DYEING

D Y E I N G,

IN the utmost latitude of the word, may be defined, The art of tingeing cloth, fluff, or other matter, with a permanent colour, which penetrates the substance thereof.—It is, however, commonly restrained to the art of tingeing silk, wool, cotton, and linen, with different colours; and, as such, is practised as a trade by those who do not meddle with any of the other branches, as staining of leather, &c.

The dyeing art is of great antiquity; as appears from the traces of it in the oldest sacred as well as profane writers. The honour of the invention is attributed to the Tyrians; though what lessens the merit of it is, that it is said to have owed its rise to chance. The juices of certain fruits, leaves, &c. accidentally crushed, are supposed to have furnished the first hint: Pliny assures us, that even in his time the Gauls made use of no other dyes. It is added, that coloured earths and minerals, washed and soaked with rain, gave the next dyeing materials.—But purple, an animal juice found in a shell-fish called murex, conchylium, and purpura, seems from history to have been prior to any of them. This indeed was reserved for the use of kings and princes; private persons were forbidden by law to wear the least scrap of it. The discovery of its tingeing quality is said to have been taken from a dog, which having caught one of the purple fishes among the rocks, and eaten it up, stained his mouth and beard with the precious liquor; which struck the fancy of a Tyrian nymph so strongly, that she refused her lover Hercules any favours till he had brought her a mantle of the same colour.

Pliny seems to ascribe the invention of the art of dyeing wool to the Lydians of Sardis: Insicere lanas Sardibus Lydi; where the word incipere must be understood. But a modern critic suspects a false reading here; and, not without reason, for Lydi substitutes Lydia, the name of a city on the coast of Phoenicia, where the chief mart of the purple dye was.

After the Phoenicians, the Sardinians seem to have arrived at the greatest perfection in the dyeing art; inasmuch that purpura Sardinorum, Sardinian dye, passed into a proverb among the Greeks. Till the time of Alexander, we find no other sort of dye in use among the Greeks but purple and scarlet.—It was under the successors of that monarch that these people applied themselves to the other colours; and invented, or at least perfected, blue, yellow, green, &c.—For the ancient purple, it has been long lost; but the perfection

to which the moderns have carried the other colours, abundantly indemnifies them of the loss. It is still, however, greatly to be doubted whether the permanency of the modern colours at all equals that of the ancient ones; though it is certain that the former greatly exceed them in brightness.

SECT. I. Theory of Dyeing.

BEFORE we can enter into any consideration of the true theory of dyeing, it is necessary to make the following observation concerning the practice, namely, That salts are almost the only means we are acquainted with by which any colouring substance can be made to fix itself upon those matters which are the common subjects of dyeing. A solution of cochineal, for instance, will of itself impart no permanent colour to a piece of woollen cloth put into it. The red colour of the cochineal will indeed stain the cloth while it remains immersed in the solution; but as soon as it is taken out and washed, this temporary stain will immediately vanish, and the cloth become as white as before. If now the cloth is dipped in the solution of any saline substance, alkalies alone excepted, and then immersed in the solution of cochineal for some time, it will come out permanently coloured; nor will the colour be discharged even by washing with soap and water. If a quantity of salt is added to the solution of cochineal, and the cloth put in without being impregnated with any saline substance, the effect will be the same; the cloth will come out coloured; only in this last case, it must be well dried before washing it with soap, or most of the colour will be discharged.

By comparing this with what is delivered under the They operate article Coloring-Making, n^o 13, 14, we shall be able to form a pretty rational theory of dyeing. It is there remarked, that a saline substance (solution of tin in aqua regia) had a surprising power of coagulating the colouring matter of certain solutions, such as cochineal, Brazil-wood, logwood, &c. If therefore a piece of cloth is previously impregnated with this solution, and put into the colouring one, it is plain that some part of the colouring matter will be coagulated by the solution remaining in the cloth, in the very same manner that it would have been if a small quantity of the saline solution had been poured into the other. The cloth therefore will take up a part of the colouring matter, which cannot be discharged but by entirely discharging the solution of tin. This, however, seems to unite

itself with the cloth very firmly, so that scarce a particle of colour will be discharged by washing in plain water, or even with soap; nor can the whole be taken out without boiling the cloth in a solution of fixed alkali.

Though solution of tin produces this coagulation in the most remarkable manner, it is not to be doubted that the same power is possessed in some degree by most of the neutrals and imperfect salts. Alum possesses it very considerably, though not so much as solution of tin; and hence that salt is very much used in dyeing, as well as sugar of lead, which also has a very strong power of coagulation. The process of dyeing, therefore, seems to be most analogous to that of the coagulation or curdling of milk. Before it has suffered this change, the milk is easily miscible with water; but after it is once coagulated, the curd, or caseous part, is very difficultly soluble in any liquid whatever. In like manner, the colouring matter in the solution of cochineal, before the cloth is put in, is easily soluble in water, and may be diffused through any quantity of fluid: but no sooner is the cloth dipped in it, than the saline substance contained in the cloth coagulates that part of the colouring matter which lies in immediate contact with it; and as all the fluid successively comes into contact with it, the whole of the colour is by degrees coagulated and deposited on the cloth.

To account for the strong adhesion of the colour to the dyed cloth, several hypotheses have been formed. One is, That the fibres of wool, silk, &c. are hollow tubes; that the colouring matter enters them; and, after being there coagulated, shows itself through the fine transparent sides of the tubes.—Another considers these filaments as solid lengthwise, but having all round their sides an infinite number of small pores like the extremities of the fine absorbing and exhalating vessels of the human body. In these pores, according to the hypothesis, the colour is lodged; and as the pores are placed exceedingly close to one another, the fine threads appear to our eyes of one uniform colour.—A third is, That the fibres are solid, or at least with respect to us may be considered as such. The saline substance, whatever it is, that is employed to make the colour strike, sinks into the surface, partly corrodes and unites itself with it into a third kind of substance no longer soluble in plain water, nor even easily by soap, but which still preserves its coagulating quality. According to this hypothesis, the dye lies entirely on the outside of the stuff, and continues as long as the effect of the salt continues upon the fibres of the matter to be dyed.

Concerning the truth of these hypotheses, or indeed any others that can be invented, it is impossible to bring any decisive proof. It seems, however, more probable, that the process of dyeing is accomplished by a coagulation of the colouring matter itself, rather than by any agglutination of it to the fibres by means of a vitriolated tartar, as Mr Hellot supposes. According to this gentleman's theory, a vitriolated tartar is generated in every process for dyeing, and proceeds from the acid of the alum and alkaline basis of the tartar used in the preparations, or in some of the dyeing ingredients themselves. He supposes that the pores of the stuff are cleaned and enlarged by the preparatory salts, and by the boiling water, in such a manner as to

receive the colouring particles, which particles are afterwards detained by the contraction of the pores occasioned by cold; and further, that these pores are lined with a saline crust of tartar or vitriolated tartar.

On this theory the translator of the Chemical Dictionary has the following observations. "Mr Hellot has not shown that pure fixed alkali is incapable of producing the effects which he attributes to his tartar and vitriolated tartar; and both these salts, though they are difficult of solution, and require a great quantity of water for this purpose, will yet dissolve at last; and therefore, if the colouring particles were fixed chiefly by means of these salts, they might be washed out by a large quantity of water; which we find to be contrary to experience.

"We shall find it more difficult to substitute a true theory than to refute that of Mr Hellot. Many experiments ought to be previously made. Nevertheless, it may be observed, That the colorific particles of most substances used in dyeing seem to be insoluble in water, in spirit of wine, and even in alkaline lixiviums: that their diffusion through these liquids is caused merely by their adhesion to certain gummy and resinous particles: and that they may be disengaged from those gummy and resinous matters, by applying a piece of stuff to which they have a greater adhesive power, which seems to be the case of the root-coloured and blue dyes; or by applying another substance to which these particles have a greater power of adhesion; such as the earth of alum, in those dyes where that salt is used, together with some other substance, as fixed or volatile alkali, capable of decomposing alum; or as the ferruginous earth of the green vitriol in black dyes, to which the colorific particles of the galls adhere; which earths are capable of applying themselves and of adhering to the stuffs. The separation of the colouring particles from the gummy and resinous matters is probably facilitated by the addition of acids and neutral salts, which may coagulate in some measure the vegetable matters, and leave the colorific particles disengaged; so that they may apply themselves to the stuff, or to the earths above mentioned."

In a treatise on this subject by M. de Apligny, the nature of the different substances usually subjected to this operation is particularly considered. These are wool, silk, cotton, and linen. Wool was probably the first substance to which any kind of dye was applied, and which might probably have been done even in the fleece, while mankind, in their rude state, wore the skins of animals. When some further progress in arts was made, and the method of manufacturing wool into worsted and cloth discovered, the dye would then be applied to it; but it was not till a considerable time afterwards that silk and cotton were known; and the art of dyeing linen is mentioned as a new invention even in the time of Pliny.

Wool, according to our author, consists of tubes, which, like hair, contain a medullary substance, but throughout their length are sieves with an infinite number of lateral pores; and in proportion to the greater or lesser number of these pores, the woolly fibres are more or less curled. The reason assigned for this is, that "the more interruptions there are in the continuity of any body, the more flexible it will be; the fibres of the wool therefore being curled must have many

many pores, and consequently great room for the extraneous substance which may be not only lodged in the exterior pores, but even penetrate into the whole extent of the tubes, after the medullary substance has been expelled. It is not therefore to be wondered at, if wool, being of all substances that are made into stuffs the most porous, should be the most easy to dye, and imbibe the greatest quantity of colour."

Silk, according to our author, may naturally be supposed to proceed originally from the mucilage of the mulberry leaf on which the animal feeds, and which he imagines is converted into an animal substance by a combination with volatile alkali; but which, by the evaporation of a thin oil, and part of this alkaline matter, becomes tough and hard. An example of something similar to this is observed on the leaves of the ros solis, on which there are found some drops, which being touched while the sun shines upon it may be drawn out into fine and very white threads. The consolidation of the silk is also promoted by a yellow substance with which the animal impregnates the thread; and this seems to be a concrete oil something similar to wax. Silk thread therefore is nothing else than a continued series of molecules of this indurated gluten: but as in this defecation the molecule will remain at unequal distances, there will necessarily be inequalities, and consequently pores in the thread; but as these pores are only on the surface of the thread without any interior concavity as in the wool, it follows, that silk can admit no particles into its pores, but such as are extremely subtile and in very small quantities; that even the particles admitted require a stronger mass or fixing substance than wool, since they are only superficial, and incapable of penetrating. Hence silk is much more difficult to dye permanently than wool, and requires likewise a much greater quantity of colouring materials; two ounces and a half of cochineal being required to give the same shade to a pound of silk that one ounce will give to a pound of wool. For the same reason also the colours on silk are less permanent than on wool.

Cotton being a true vegetable substance must necessarily have its fibres hollow like wool, that the juices may circulate properly; but as these are a great deal finer, the cotton is therefore much more difficult to dye. The exterior and lateral pores of cotton are likewise filled with a kind of oil, which it is necessary to expel before the dye can be given.

Flax may likewise be supposed porous, but that its pores are much smaller than those of any of the substances already mentioned. The detached and separated fibres resemble silk in some degree, only that, being more dry and compact, they take the dye with still more difficulty than even cotton; and from the different textures of these substances we may reasonably ascribe the different shades which are taken by them even when the same dyeing ingredients are made use of. This holds good also with respect to stuffs differently manufactured, though of the same kind; the pores being necessarily contracted by certain kinds of fabrication, whence they receive a smaller quantity of the dye: and hence scarlet cloth, when cut, appears white internally, the colouring atoms being too large to penetrate it, which, however, does not happen in the stuffs which have been previously dipped in solution of alum.—A difference of shade will also be oc-

casioned by the different positions and delicacy of the fibres of the stuff; and by this also a difference is made in the brightness of the colour.

With regard to the operation of those substances commonly made use of for fixing the dye, our author remarks, that lime seems destined by the Author of nature for binding and uniting the two seemingly opposite substances of salts and earth. "Fire (says he) makes it soluble in water, and therefore easily used; but it again becomes insoluble by the contact and influence of the air; and these properties render it capable of forming, when united to other bodies, an unalterable cement." We know several mixtures of this kind, of which lime is the basis, and that in consequence of these properties it confirms the solidity of many colours.

Alum has the property of attracting the colouring particles of the dye as well as of fixing them; and Pliny informs us that this property was known to the ancients. They made use of certain earths of the argillaceous kind, which they called creta argentaria, salumisia, and emularia, to imbibe the colour from infusions of dyeing ingredients; and they became much sooner saturated with the colour than wool itself. There are two kinds of alum made use of in dyeing, viz. roch alum and Roman alum. The first is always used for blues and the colours inclining to black; but as this generally contains some particles of iron, the Roman alum is preferred for the more lively colours, as it contains nothing capable of tarnishing their beauty. The colours are brightened by the whiteness of the earth, while its tenacity, produced by some kind of unctuousity with which it is combined, makes it more solid; and the plastic quality of the earth makes it take the form of the pores in the substance to be dyed; whence a greater permanency of colour must necessarily ensue.

There are several other saline substances made use of in dyeing, particularly nitre, sea-salt, sal ammoniac, and tartar, &c. By the three first the red colours are always rendered more dark-coloured, while the others enliven the colour and give it an orange hue. Neutral salts with a metallic basis serve to strengthen the colour, which varies its shade according to the nature of the metallic substance with which it is combined. Green and blue vitriol are the most commonly used in this art.

In explaining the theory of the art of dyeing, our author considers the whole as an effect of attraction; and in order to set forth this matter in a proper light, it is necessary, in the first place, to explain the conditions requisite for the action of bodies upon one another in this way. These conditions are, 1. That the attractive power be mutual in both. 2. That they should be placed at a distance from each other proportioned to the force of attraction. 3. That this force be superior to that by which the colouring matter is attracted by the water. Hence it is necessary for dyeing stuffs of any kind, that the dye should consist of small particles suspended in a liquid, in such a manner that they may be separated by a substance which has a greater affinity with these minute bodies than water. Some of these substances, however, are not attracted by the earth of alum, and these enter the pores of the cloth without its assistance; but in such as require the assistance of alum, the particles are fixed by the power of attraction, at the same time that the acid of the

alum is softened by its combination with the principles of these particles; this acid having served merely as a vehicle for distributing equally into all the pores of the stuff that earth which it held in a state of the greatest possible divisibility.

Our author next proceeds to contest the theory, that salts, even such as are the most insoluble, can maintain their stability in the pores of the stuff, however insoluble the salt may be in water. He observes that this insolubility, however great, could not prevent a great quantity of it from being carried off by water, and consequently the colour from being injured by the decomposition of these salts; but fixed earth, such as that of lime and alum, which from its nature obstinately retains the phlogistic principles of all colours, must necessarily produce such as cannot be destroyed but by the strongest acids.

Colours, in the opinion of our author, depend entirely upon phlogiston. It is well known that, by the simple addition of any salt to an oily, vegetable, and colouring substance, we may either change or totally expel its colour; because any salt, either simple or compound, destroying the combination then subsisting, a new reflection of the rays of light must necessarily take place. In such substances therefore as cannot have their colour affected by any salt, the phlogiston is most probably in the most perfect combination with the other principles. Were we thoroughly acquainted with this combination, we should be able to make perfect compositions for dyeing, similar to what artificial cinnabar is for painting: but though we certainly know the effects produced upon some kinds of oils by salts, and can decompose some colouring substances and separate their principles; we are still unacquainted with the manner in which these principles are combined; and therefore every effort of this kind has hitherto been found insufficient for the purpose.

"As the colour (says our author) depends upon the shape or figure of the constituent particles of the colouring bodies, the shade may be varied by changing their figure, but the permanency of the colour is at the same time diminished; because it is impossible to produce this change without altering the principles to which they owe their permanency; and this is the case with cochineal. The shades of its colour are easily varied by acids and alkalies."

M. de Apligny then proceeds to account for the action of acids and alkalies upon colouring substances. Cochineal is rendered darker by alkalies, and always becomes of a deep purple on adding them; and the volatile alkali is found to be more efficacious in this respect than the fixed kind. These salts he supposes to produce this effect, because they are natural solvents of animal substances; which, however, they are incapable of dissolving without combination, causing only a composition without the dissipation of any principle. This combination gives a degree of density to the colouring particles which they had not before; and thus inclines them to black, by occasioning a greater degree of refraction in the pencils of rays. Acids, on the other hand, especially those of the mineral kind, burn the oil, and absorb the phlogiston, which is the principle of all colours. By the violence of their action a part of the phlogiston and volatile alkali eva-

porates, the colouring matter becomes more rarefied, and reflects a greater number of the rays of light; whence it necessarily acquires a colour nearly yellow, and even quite so if a proper quantity be added; this being, according to our author, of all colours the nearest to white or transparency. Hence it is not customary for dyers to make any use of fixed alkali when cochineal is the colouring substance, as it would make too great an alteration in the consistency, and, by mixing with the animal oil, form a soap which would render the colour miscible in water, and consequently of the false kind of dye; the oil already mixed with fixed alkali being no longer at liberty to combine with the earth of alum. But after the substance has been already dyed, the fixed alkali may then be used with advantage in some cases; because the colouring substance being already converted into what our author calls a masse, cannot be dissolved by the menstruum unless the latter be used in very great quantity.

Acids, according to M. de Apligny, are more destructive in their action than alkalies; and the oil of vitriol, formerly used, always containing some ferruginous particles, a kind of Prussian blue was formed, which rendered the colour purple rather than otherwise; and even by simple boiling in an iron vessel, the solution of cochineal always assumes a purple colour. The activity of spirit of nitre, which has been substituted in place of oil of vitriol, is so great, that it has been found necessary to give it a basis on which it might in part exhaust itself, and, by communicating part of its phlogiston, render it less greedy of the cochineal. This basis is tin, which formerly was dissolved by spirit of nitre, but now by aqua regia, which was found to dissolve it more completely. Our author's method of using this solution, however, is not by diluting it in water, and then by dipping the stuffs in it previous to their being dyed. "This preparation (says he) would not be sufficient; for by diluting with a great quantity of water, a part of the calx would precipitate and be reduced into particles larger than when dissolved in acids, especially if used alone and separate from the dye; the acid in that case not acting on the colour with sufficient force to enliven it. Only part of this solution, therefore, is added to the cochineal liquor; and the acid then abandoning the tin, and combining with the oil of the cochineal, the calx of the metal seizes the colouring matter as it precipitates, and, as Mr Hellot observes, forms a kind of lacker which infiltrates into the pores of the stuff, and is there retained by a gluten given by the starch which was added to the dyeing liquor. Hence it is easy to conceive why the scarlet dye is much less solid than the crimson; the lacker being much drier than the simple colouring particles of the cochineal, is in this state nearer to the nature of the mineral colours. The oil and the animal gluten, which in the crimson dye form with the earth of alum a masse, are destroyed by the acid, and the starch then added is an insufficient substitute."

The same thing that has here been mentioned of cochineal applies equally to gum-lac and kermes; both of which afford a scarlet dye. The kermes, he thinks, has the advantage of being composed of finer particles, which more easily penetrate the pores of silk or cotton. Silk indeed, on account of the smallness of its pores, takes up only a part of the cochineal; but it extracts the

the whole of the colour from the cochineal, and the colour is also more fixed, probably because the shrub on which the insect is nourished communicates its affinity, or contains a greater quantity of oil. Cotton may likewise be dyed with kermes, though cochineal cannot penetrate its pores.

But in whatever way the salts used in dyeing do act, it is certain they are capable, except in a very few instances, of fixing and giving a lustre and permanency to the colour which otherwise could never be obtained. The exception to this general rule most commonly known is that of indigo. This is a fine blue fecula produced by fermentation from the leaves of the Indian plant called anil. It is very difficult of solution; however, it may be dissolved by alkaline salts, concentrated oil of vitriol, orpiment, or combinations of sulphur with quicklime. If a quantity of indigo is dissolved in a fixed alkali (for volatile alkalies will not dissolve it), the solution is always green, which is the natural colour produced in all vegetable blues by the alkali: but if any piece of stuff is put into this solution, though it remains green while immersed in the liquid, the moment it comes in contact with the air, the dissolving power of the alkali is totally destroyed; the indigo is precipitated upon the cloth, resumes its native colour, and dyes the cloth blue.

The cause of this precipitation is very difficult to be investigated. Perhaps it may be owing to an attraction of fixed air by the alkali from the atmosphere, which renders the salt unable to dissolve the indigo any longer. The adhesion of the colour seems merely owing to an attraction between it and the cloth; for the alkaline salt can contribute nothing to this, but would rather have the contrary effect. Perhaps, however, the great solvent power possessed by alkaline salts, by perfectly clearing away every kind of fordes, may bring the indigo and cloth into nearer contact with each other, than when it is dissolved in any other way; and consequently the attraction will in these cases be the stronger. This seems to have some probability; for when indigo is dissolved in vitriolic acid, as in dyeing Saxon blue, the colour is much more easily discharged.

Another exception is in the juices of some vegetables, such as the nuts of the anacardium. This produces, without addition, a most deep and lasting black, never to be washed out or discharged by any means whatever. Several other plants are to be found in different parts of the world, which give an indelible black stain upon linen without addition; and the colouring matter of these seems to adhere by means of a very tenacious gluten, with which it is mixed, and which, when once thoroughly dried, can never be again dissolved. In this respect, these black staining colours seem analogous to the purpura of the ancients; which stained indelibly without addition, and was of an exceedingly viscous and adhesive nature.

SECT. II. Practice of Dyeing.

THE materials for dyeing different colours are so many and various, that an enumeration of them all is scarce to be expected. The same difference, however, takes place among the materials for dyeing which we have observed to take place among those for Cocoon.

Making. Some ingredients produce durable colours, which cannot be discharged either by exposure to the air or by washing with soap: others, though they may be made to stand the action of soap pretty well, cannot by any means be enabled to resist the action of the air. These are distinguished by the different names of true and false, permanent and fading, &c.; nor is there any method yet discovered of giving the false colours an equal degree of durability with the true ones. This hath been attempted by mixing a permanent and a fading colour together; in which case it was thought that the former would impart somewhat of its durability to the latter: but this hath always been found to misgive; the fading colour soon flying off, and leaving the permanent one behind. Nay, in many cases this does not even happen; for, by some means hitherto not accounted for, the volatile colour imparts its volatility to that which would otherwise be permanent. The same hath also been attempted by dyeing a piece of stuff partially with a fading colour, and then completing the dye with a permanent one. In this case it was hoped that the fading colour being covered over, and defended from the injuries of the air by the permanent one, would necessarily become equally durable, or at least remain a much longer time than if the stuff was dyed with it alone. But this also hath been found ineffectual; and the fading colour hath been dissipated as soon when covered with a permanent one, as when left without any such cover.—Solution of tin in aqua regia will give most of these fading colours an high degree of beauty, and some share of durability, though even that is not able to make them equal to the others.—The most permanent dyes we have are cochineal and gum lac for fine reds and scarlets; indigo and woad for blue; and, when mixed in different proportions with cochineal or lac, for purple and violet colours. Weld, and some other vegetables, for yellow; and madder for coarse reds, purples, and blacks.—The fading colours are much more numerous. In this class are included Brazil-wood, logwood, peach-wood, red-wood, fustic, turmeric root, annotto, archil, &c. &c.

With regard to the salts made use of in dyeing, it hath been but too often customary to jumble together such a quantity of different ones, that it was not only impossible to know in what particular salt the virtue resided, but often the efficacy of the whole hath been totally destroyed, and the colour entirely spoiled by such injudicious management. It is proper, therefore, where a mixture of two or more salts is intended to be made for dyeing, first to try the change of colour produced by each of the salts upon the colouring substance. If the colours are nearly alike, the mixture may be safely made as to that particular. But if the two colours produced by the different salts are very different from one another, to mix them together must be very injudicious. Thus, suppose you want to dye scarlet, solution of tin in aqua regia produces the necessary change of colour on the decoction of cochineal, and converts it into a high flame-colour, which shows it to be a proper ingredient; but to the solution of tin, it would surely be the greatest absurdity to add a quantity of saccharum faturni, the effect of which is to change the colour of cochineal to a dull purple. But though the salts taken separately should produce a colour nearly similar, another thing must be regarded, namely, whether

thor.

ther they can be mixed with safety to one another? It is the nature of many salts to destroy one another whenever they come into perfect contact by being dissolved in water. Thus, solution of tin and faccharum saturni destroy one another; and so do solution of tin and tartar or cream of tartar. To mix these together must therefore be absurd; and yet we find this last mixture ordered in almost every receipt for dyeing scarlet. It is also to be observed, that a mixture of different salts ought never to be made, out of a notion that the colour will keep the better on that account; for most commonly it will keep the worse. A single salt will answer for this purpose better than a hundred. A mixture should only be made where it is necessary to produce the colour desired; and if a dyer proceeds in this simple manner, he may not only attain to great perfection in the art from his own experience without being taught by others, but even make considerable discoveries; as dyeing is at present far enough from being brought to perfection.—The salts chiefly to be used in dyeing are fixed alkalies: solutions of tin in the vitriolic and marine acids, and in aqua regia; sugar of lead; cream of tartar; alum; oil of vitriol; and solution of iron in the acetic acid. By means of these, almost all kinds of colours may be dyed at an easy rate, and with very little trouble.

With regard to the operative part of this business, M. Hellot observes, that the whole depends on the use of some colours called by the workmen primitives, but which have no relation to the colours called primitive by Sir Isaac Newton. The primitive colours used by dyers are in number five, viz. blue, red, yellow, fawn or root colour, and black. Each of these furnish a great number of shades, both according to the nature of the ingredients themselves, and the acid or alkaline substances with which they are mixed. Of these five colours only two should be prepared with ingredients which produce no colour themselves, but which, by their acidity, and the fineness of the earth they contain, dispose the pores of the substance to receive the dye. Those colours which in a more particular manner require such a preparation are the red and yellow, with such others as are derived from them. Black requires a particular preparation; but blue and fawn colour none, at least for wool; it being sufficient for the purpose to scour and soak this substance well; after which nothing more is required than to plunge it into the vat, stirring it well about, and letting it remain for a longer or shorter time as the colour is intended to be more or less deep.

The ingredients used in dyeing blue are by our author determined to be three in number, viz. pastel, wood, and indigo.

Pastel, called in Latin ifatis or glossum, is prepared by gathering it when come to maturity, suffering it to rot, and then making it up into balls for drying. For this purpose it is cultivated in Languedoc, and is made up into balls of 150 or 200 pounds weight. These resemble a collection of little dry lumps of earth intermixed with fibres of plants. For extracting the colour, the dyer must provide himself with large wooden vats of a magnitude proportioned to the quantity of stuff to be used. Mr Hellot recommends them from ten to twelve feet in diameter, and six or seven in height. They should be made of staves six inches

broad and two inches thick, bound with iron hoops about two or three feet asunder. They are to be sunk in the ground for the more easy management of their contents, which is done by means of hooks fastened to the end of a staff, the length of which is proportioned to the diameter of the vat. The bottom is made of lime and cement, though it might be made of wood, were it not for the difficulty of getting a wooden bottom strong enough to support the weight. The vats used for dyeing cottons of a blue colour, as M. de Apligny informs us, are generally formed of large brandy pipes newly emptied, or of oil hogheads containing about 500 quarts. Before the latter are made use of, they ought to be well cleansed, by flaking lime in them, and scrubbing with a broom till the oily matter is thoroughly dissolved by means of the lime.

The preparation of the blue vat is the most difficult operation in the whole art of dyeing; and for this our author gives the following directions: "Your copper cauldron should be placed as near as possible to the vat, and then filled with pond-water. If the water be not sufficiently putrid, you put in a handful of hay, viz. two or three pounds, with eight pounds of brown madder, or the bark of the root. If you could have the old liquor of a madder vat, it would save fresh madder, and have a better effect. The fire should be lighted about three in the morning, and the mixture should boil an hour and a quarter; though some continue the boiling for two hours and an half or three hours. The liquor is now to be conveyed into the vat by means of a spout, the vessel being very clean, and having a hatful of wheat bran at the bottom. The pastel balls are to be put into the vat one after another while the liquor is running into it, that they may be more easily broken, stirred, and mixed with the rake, an instrument composed of a strong semicircular piece of wood, with a long wooden handle. The mixture should be continually stirred till all the hot liquor is emptied out of the copper into the vat; and when the latter is rather better than half full, it should be covered with a lid a little larger than the circumference. There should also be a cloth put over it, to confine the heat as much as possible; after which the whole should be allowed to remain four hours. It ought then to be uncovered, in order to mix it thoroughly, and to give it air. About an handful of lime ought now to be put in for every ball of pastel; and after scattering in this substance, the vat should again be mixed and covered as before, except about an handbreadth to let in the air. In four hours after it should again be stirred, but without giving it any more lime; then it is to be covered and suffered to stand for three hours longer, leaving a small opening for air as before. At the end of three hours it may again be uncovered and well stirred; and if it be not yet ready and come to, according to the language of the dyers, that is, if the blue does not rise to the surface, but that it still foams, which may be known by striking with the flat of the rake, it will be necessary, after stirring it well, to let it stand an hour and an half longer, watching it carefully during that time in case it should cast blue. You then supply it with more water till the vat is full, putting in as much indigo as you think proper.

"The indigo used for this purpose should be in solution; and in order to dissolve it you must have a separate

parate cauldron and furnace, and the vessel sufficient for dissolving 80 or 100 pounds of indigo must contain 30 or 35 buckets of hard water. This should be made into a lixivium, by putting 25 buckets of clear water into the copper with the addition of a hatful of bran, 12 or 13 pounds of madder, and 40 of good pot-ash; that is, half a pound of alkaline salt and two ounces and a half of madder to each pound of indigo. It should boil quickly for three quarters of an hour; after which the fire should be taken away from the furnace, and the residuum stand for half an hour, in order to let the sediment fall to the bottom. The clear liquor is then poured into a clean cask placed close to the copper. Take out the grounds at the bottom of the copper, wash it clean, return the lixivium into the copper, light a small fire under it, and at the same time put into the copper 80 pounds of indigo reduced to a gross powder. The liquor should then be made very hot, but not suffered to boil; and to facilitate the solution, it must be kept continually stirring with a small rake, to prevent it from gathering into lumps, or from burning to the bottom of the copper. The liquor should be kept moderately hot, and of as equal a degree of heat as possible, by throwing into it from time to time some lixivium of lime, which should be at hand ready prepared, in order to cool it. As soon as you perceive that there are no longer any lumps in the bottom of the copper, and that the indigo is well dissolved and diluted, the fire is to be withdrawn from the furnace, leaving only a few hot cinders to keep it warm. Cover up the copper then, and put in a pattern of stuff, which ought to be green when taken out, and turn blue immediately on being exposed to the air. Should this not be the case, some fresh and clear lixivium, prepared as just now directed, must be added.

"In preparing the patten-vats, one common dye-house kettle full is to be put in for every ball of patten; the vessel is then to be filled within six fingers breadth of the edge, when it is to be well mixed and covered as before.

"An hour after the vat has been supplied with water, it must have two measures (about two handfuls) of lime for every ball of patten, or in proportion as it is thought that it will be required; but as some kinds of patten require much less preparation than others, it is impossible to give any accurate directions upon the subject. In general, however, the lime should not be scattered in till the vat be well stirred.

"Having again covered the vat, a pattern is to be put in at the end of three hours, which should also be kept three hours immersed in the liquor, when it is to be taken out, in order to examine the state of the vat. The pattern, as has already been observed, ought to be green when immediately taken out, but instantly to turn blue; and if it is of a good green, you stir the vat, adding one or two handfuls of lime, and then cover it. Three hours afterwards it is to be stirred again, adding more lime if necessary. Cover it then for an hour and an half longer; and when the matter is settled, immerse a pattern, which must remain for an hour, and then be inspected to know the state of the patten. If the pattern be of a good green when taken out, and becomes a deep blue when exposed to the air, another pattern is to be put in, in order to ascertain the effect of the vat. Should the colour of the pattern be suffi-

ciently high, the vat is to be filled with hot water, or, if it can be procured, the liquor of an old madder vat, and then stirred again. If the vat wants lime, a sufficient quantity must be added according to the smell, and as it may be found necessary during the working. This being done, and the vat brought to a proper state, it is to be once more covered for an hour; after which the stuffs are to be immersed in it."

This operation is supposed by some dyers to be impracticable, except upon a very large scale; but M. Hellot's method of preparing a blue vat on a small scale. Hellot has made some experiments on this subject, which seem to evince the contrary. For this purpose he took a little barrel containing about 25 gallons, and put it into a copper full of water kept carefully heated. He then put 20 gallons of water into a small copper with an ounce and a half of madder, and a very small handful of dyer's weed; which last, however, he does not suppose to be of any use. Having made the whole to boil together for three hours, he poured all the liquor into the barrel about nine in the evening, previously putting into it two small handfuls of bran. At the same time he added four pounds of patten; and having stirred it well for a quarter of an hour, he covered it up, and took care to have it stirred every three hours during the night. It is customary to put some four water into the large vats, but this was omitted in the present case; and the bran, which soured with the liquor, was found to be a sufficient substitute. Next morning the mixture was found to be in a state of fermentation, frothing up and making an hissing noise. On mixing it well, and adding an ounce and an half of slaked lime, the froth was increased; and as the smell became stronger, it was judged proper to add a little more patten. At half an hour after ten the vat smelt stronger of the lime; a pattern was put into it; and at the expiration of an hour, it was taken out green; and which, on being exposed to the air, became blue. On being stirred, another pattern was put in about an hour afterward; which having also remained an hour immersed in the liquor, came out afterwards of a deeper blue than the former. At half an hour after twelve two ounces of indigo, not dissolved, but only powdered, sifted, and diluted with hot water, were put in, with about the bigness of a walnut of the cendres gravelles or burnt lees of wine, which contain a large quantity of alkaline salt; and every two hours afterwards a pattern was put in an hour after stirring the vat, letting each also remain an hour in the liquor. This was continued till ten o'clock; and the last patterns were not only evidently darkest, but of the brightest colour.

The last pattern showed that the lime was exhausted; but on account of the lateness of the hour, our author added only another half ounce of lime, and an hour after put in another pattern; which after having remained an hour in the liquor, was taken out more blue than the rest, though the colour had been rendered less lively by the lime. Two other patterns put in during the night were still darker, though the colour was somewhat dull; an evidence that the lime was not yet exhausted. The paste which lay at the bottom was of a yellowish brown when taken out, but by exposure to the air became of an olive green. Under the surface it appeared of the same colour if moved with the hand, but instantly became green, smelling rather strong, though not very much of the lime. The liquor

itself was of the colour of beer, but the scum or froth of a blue colour. Patterns were now put in every two hours till two in the afternoon; when that which was taken out appeared of such a fine blue, that it was judged proper to fill the vat. For this purpose about eight gallons of water were put into a little copper with a quarter of an ounce of madder and a handful of bran; and when it had boiled for half an hour, the liquor was put into the little vat for three hours. On stirring and letting it then remain for an hour afterwards, a pattern was put in, which in an hour's time was taken out of a beautiful blue. An ell of serge was then immersed by means of what our author calls a croft; which is an iron hoop with a net fastened to it, the meshes of which are about an inch square; and the whole may be suspended at any height required by means of three or four cords fastened to it. The serge had no other preparation than being made thoroughly wet; nevertheless, in about a quarter of an hour it was taken out very green, and on being wrung out turned blue; but on a second immersion for another quarter of an hour, the colour turned out much more lively and brighter than could have been expected. The experiment was repeated with a pound of worsted; but the vat had been so much exhausted that it came out only a sky blue; however, by sprinkling in about half an ounce of fresh lime, the colour was afterwards made sufficiently deep.

For working this vat our author gives the following directions. 1. It is in a proper state for working, i. e. for imparting the blue colour to the stuffs put into it, when the sediment or grounds at the bottom is of a fine brown green; when it changes upon being taken out of the vat: when the froth which rises to the top is of a fine Persian blue; and when the pattern, which had been steeped for an hour, is of a fine green colour. 2. The vat is also in a proper state for working, when the liquor is clear and reddish, and the drops which adhere to the rake are of a brown colour. 3. When the liquor is neither harsh nor too greasy to the feel, and when it smells neither of lime nor of the lixivium. 4. It may be known when too much lime has been put in, by the colour of the pattern immersed in the liquor; which, instead of being a fine grass green, will be only a dirty greyish blue, or some other colour of that kind. The same thing may likewise be understood when the sediment does not change colour; when there is scarce any efflorescence on the vat; and when the liquor smells only of lime or lixivium.

In order to rectify the state of the vat in this case, several methods have been recommended by practical dyers. 1. Some use tartar or bran, adding a quantity of either as occasion may require. 2. Others attempt to correct it by throwing in a bucket of urine. 3. Sometimes they use a large iron stove, which may reach from the grounds at the bottom to the top of the vat. This machine is furnished with a grate about a foot from the bottom, and an iron funnel, one end of which commences with the grate, and communicates with the external air. On forcing down the stove to the bottom of the vat, where it ought to be retained by iron bars, the heat of the stove will force up the lime to the top, where as much as is required may be taken out by a sieve. 4. Some

dyers correct a vat which has got too much lime with urine and tartar: but the best method, according to our author, is to put into it a sufficient quantity of bran and madder; and if the excess of lime is not very great, it may be allowed to stand four, five, or six hours, or more, adding to it two handfuls of bran and three or four pounds of madder, which should be slightly sprinkled on the top without any covering. At the end of four or five hours it should then be stirred by a rake, and a pattern put in to try the effect of it. If the blue does not rise until it be cold, it ought to have time to recover, by allowing it to stand without disturbance, which sometimes requires whole days to accomplish; but, in general, the lime which seems to want strength to carry on the fermentation, revives and prevents the vat for some time from yielding any colour. To bring it forward, some bran and madder should be sprinkled on the top, besides an addition of two full baskets of fresh pastel, which assists the liquor, when heated again, in dissolving the lime. 5. The vat ought now to be frequently tried by putting in a pattern, that from one hour to another you may be able to judge by the green colour how far the lime has operated. Thus the operation may be accurately conducted; for when the vat has suffered either by too much or too little lime, it is very difficult to manage it. 6. If, during the time that you are thus employed in retrieving the vat, it should cool too fast, you must endeavour to preserve the heat by emptying some of the liquor, and replacing it with hot water; for when the liquor grows cold, neither the pastel nor lime are consumed but in very small quantity. The action of the lime is also retarded by too great a degree of heat; and in this case it is proper rather to wait a little than to be in too great a hurry to restore the vats. 7. It is evident that the vat has suffered by not being sufficiently supplied with lime, when there are no large air-bubbles on the top of a fine blue colour, but only a settled froth of small tarnished bubbles; and when, by dashing upon the surface of it with the rake, it makes a hissing noise produced by the breaking of a vast number of these small air-bubbles as soon as they are formed. The liquor has also an offensive smell like rotten eggs, and the sediment does not change colour when taken out of the liquor. This accident will very probably take place, if you do not carefully attend to the smell of the vat, but imprudently put in the stuffs when the pastel has spent the lime; for in that case the small quantity of lime which remains will adhere to the stuffs, and will thus give them a bad colour. When this is perceived, you must immediately take them out, and add three or four handfuls of lime in proportion to what you suppose the vat has suffered, but without stirring it up from the bottom. On stirring the vat you ought to attend to the noise as well as to the smell; for if the hissing ceases, and the bad smell is also removed, there are great hopes that the liquor only has suffered, and that the pastel is not impoverished. But when the liquor smells of lime, and is soft to the feel, the vat is then to be covered, and allowed to settle for an hour and an half; after which period, if the efflorescence commences, a pattern is to be put in, and the subsequent process is to be regulated by the colour it assumes.

Some are of opinion that the pastel blue is much superior

superior to that obtained with a mixture of indigo; but it is undoubtedly much dearer, as yielding a much smaller quantity of colour: and from the experiments of M. du Fay, as well as of our author on this subject, it appears that the prejudice in favour of pastel is by no means well founded. When a vat has been heated and well worked two or three times, the same colour is frequently preferred, only taking out part of the sediment, and supplying it with fresh pastel; but for this no directions can be given, as it is evident that the whole must be regulated by the practice of the dyer. Some are accustomed to allow the same liquor to remain for years in their vats, only supplying it with ingredients from time to time; but this practice seems not to meet our author's approbation, who thinks it rational to suppose that the best colours will be made by emptying the vats entirely when they have been heated six or seven times, and cease to give any more colour.

²² Danger of reheating pastel vat when the lime is exhausted. With regard to the reheating of the pastel vats, our author further observes, that if you heat a vat when it is exhausted, viz. when deficient in lime, it will imperceptibly turn in such a manner as to be in danger of being spoiled; because the lime, already too much diminished, will be entirely consumed by the heat. The only remedy, if discovered in time, is to throw it back into the vat, to supply it with lime, and then wait till it recovers before you reheat. In this operation also care should be taken to put the grounds into the copper with the liquor; and it must not be allowed to boil, otherwise some of the more volatile parts necessary for producing a good colour will be evaporated. Some do not put the indigo into the vat until some hours after the liquor has been emptied out of the copper, and the mixture begins to recover itself. This precaution is taken lest the vat should not recover, and then the indigo would be lost. An inconvenience, however, arises from this practice, viz. that the indigo does not give out its colour freely; so that it is best to put it into the vat immediately with the liquor, and to stir it well afterwards. If a vat that has not been worked is to be reheated, it must not be skimmed as in the common operations of this kind, for then the indigo would be skimmed off; but in ordinary cases the foam is composed of the earthy particles of the indigo and pastel, with a small quantity of lime. When too much lime is added, you must wait till it be consumed. It might indeed be corrected by an addition of acid or other ingredients; but as these also consume the colour, it is better to wait the natural operation of the lime itself. Weak lime proves likewise disadvantageous, because it remains in the liquor without incorporating with the paste. When this is the case, the paste smells strong, and the liquor has a kind of sweetish smell; but both ought to be alike in this respect. The remedy is to hasten the solution by stirring it often in order to mix the lime with the paste, till the proper smell of the vat be restored, and the froth on the surface becomes blue.

²³ To slack the lime for the purposes of dyeing. To slack the lime for the purpose of dyeing, several pieces are to be thrown into water one after another, taking out each piece when it begins to ferment, and putting in another. It is then put into an empty copper or other vessel; and when fallen thoroughly

into powder, it is to be sifted through a fine sieve, and kept in a very dry cask.

²⁴ Preparation of acid waters. In this operation acid waters are sometimes necessary; the method of preparing which is as follows: Fill a copper of any size with river water; put fire under it; and when it boils, throw it into a cask in which you had before put a sufficient quantity of bran. It should be well stirred three or four times a day. Three bushels of bran into a vessel containing about 70 gallons of water have been found to answer the purpose. This water, at the end of four or five days, becomes acid; and therefore may be applied in all cases where it does not injure the preparation of the worked. It must be observed, however, that woollen fleece, by too great a quantity of acid liquor, would be rendered difficult to spin, as being in a manner glued together by the matter proceeding from the bran. It is also necessary to take notice, that the acid must not be left in the cauldron, especially if this is made of copper; because it will corrode enough of the metal to occasion a deficiency in the colour. This metal, when dissolved, gives a greenish colour.

²⁵ Dutch vats. The Dutch vats are constructed in such a manner as to require less frequent heating than those above described. The upper part of them for three feet downward is of copper, and they are almost surrounded by a brick wall at about the distance of six or seven inches from the metal. A quantity of hot embers are deposited in this interval, which maintain the heat of the vat so effectually, that it remains for several days in a state fit for working even after it becomes very weak. This is not the case with the others, which frequently give a much deeper colour than was intended, unless you suffer them to grow considerably colder; and in that case the colour is less bright.

²⁶ The woad-vat differs from that already described only in being weaker and yielding less colour; but it is prepared in the same manner. The following is a description of the woad vat, according to an experiment made by M. Hellot, similar to that concerning the pastel already mentioned.

"I placed (says he) in a cauldron a small cask containing about twelve gallons, two-thirds full of river-water, an ounce of madder, and a small quantity of weld; at the same time I put into the cask a good handful of bran and five pounds of woad. At five o'clock in the evening the vat was well stirred and covered. It was again stirred at seven, at nine, at twelve, at two, and at four. The woad was then working, as has been already observed with regard to the pastel. Some air bubbles began to rise pretty large, but in a small quantity, and of a very faint colour. It was then garnished with two ounces of lime, and stirred. At five o'clock I put in a pattern which I took out at six, and again stirred. This pattern had received some colour. At seven o'clock I put in another, and at eight stirred again. This pattern was tolerably bright: I then added an ounce of indigo; at nine o'clock another pattern; at ten stirred again, and put in an ounce of lime because it began to smell sweetish; at eleven another pattern, and at twelve stirred again. This process was continued till five o'clock. I then added three ounces of indigo. At six I tried another pattern, and at seven stirred again. It would have been now time to fill it, being in a proper state

for working, as the last pattern which had been taken out very green became a bright blue: but as I was very much fatigued, having sat up the whole night, I chose to defer it till the next day, in order to see its effect by day-light; and for this reason I added an ounce of lime, sufficient to sustain it till nine o'clock in the morning. Patterns were put in from time to time; and the last being very beautiful, I filled the vat with a liquor composed of water and a small handful of bran only. It was then stirred, and patterns tried every hour. Being in a proper state at five o'clock, it was immediately worked. It was then garnished with lime, and mixed, in order to preserve it till such time as it might be convenient to reheat.

"Two months afterwards I prepared another woad vat without indigo, that I might be enabled to judge of the solidity of the dye; and was convinced, by experiment, that it was of equal goodness with the pastel. Hence the pastel is superior to the woad only because the latter yields less colour than the other.

"The little variations to be observed in the method of setting these different vats, sufficiently demonstrates that there are many circumstances in the several processes not absolutely necessary. In my opinion, the only matter of importance, and which demands attention, is to conduct the fermentation with caution, and to avoid supplying with lime till, from the indications I have described, it appears necessary. With regard to the indigo, whether it be added at twice or all at once, whether a little sooner or a little later, is, I think, of very little importance. The same may be said of the weld, which I used twice, and twice omitted; and likewise of the pearl-ash, a little of which I put into the small pastel vat, and omitted in that of the woad. In short, it appears to me very demonstrable, that the distribution of the lime either in the setting or reheating the vats requires most attention. It must also be observed, that in setting either a pastel or woad vat, it cannot be too frequently examined; because though some are too slow, which is attributed to the weakness of the pastel or woad, others become too soon ready for working. I have seen seventy pounds of pastel lost by this neglect. It was ready for working at eight o'clock, but for want of the workman's constant inspection, he did not discover it till two hours afterwards. The paste was then entirely risen to the surface of the liquor, which smelt very sour. It was now impossible to recover it; he was therefore obliged to throw it out immediately, or it would very soon become insupportably putrid and fetid.

"This difference in the vat may be also produced by the temperature of the air, as it cools much sooner in winter than in summer. It is therefore necessary to watch very attentively, though it is seldom fit for working in less than 14 or 15 hours.

"The indigo vat (says our author) is about five feet high, two feet in diameter, and grows narrower towards the bottom, being surrounded by a wall, and a vacancy left for the embers. In a vat of this size you may put from two to five or six pounds of indigo. In order to set a vat containing twenty gallons, you boil in a copper about fifteen gallons of river-water for half an hour, with two pounds of pot-ash, two ounces

of madder, and a handful of bran. The indigo is prepared meanwhile in the following manner:

"Take two pounds of indigo, and put it into a pail of cold water, in order to separate the solid from the volatile particles, which will immediately rise to the surface. The water is then poured off, and the remaining indigo pounded in an iron mortar; you then put a little hot water into the mortar, shaking it from side to side, and pouring into another vessel that which swims, and which is consequently the best bruised. In this manner you continue to pound what remains in the mortar, still adding fresh water, in order to make the finest part rise to the surface, and so on till all the indigo is reduced to a powder so fine as to rise in the water, which is all the preparation required. The liquor which had boiled in the copper, with the grounds of the madder and pot-ash, which probably fell to the bottom, is thrown into the high narrow vat; at the same time adding the pounded indigo. The whole is then well stirred with a rake, the vat covered, and the embers put round it. If this operation was begun in the afternoon, you must renew the hot embers in the evening, which should also be repeated both morning and evening the next day: the vat should be lightly stirred twice the second day. In order to maintain the heat of the vat, you renew the embers on the third day, stirring the vat twice. You then perceive, that a shining brassy scum, divided and interrupted in many places, begins to rise on the surface. By continuing the heat, on the fourth day the scum becomes more perfect and less broken. The froth that rises upon stirring is now blue, and the vat a deep green.

"When it becomes green in this manner, it is an indication that the vat should be filled. For this purpose you must prepare a fresh liquor, by putting five gallons of water into a copper, a pound of pot-ash, and half an ounce of madder. When this has boiled a quarter of an hour, you fill the vat. You then stir it; and if it produces much froth, it will be in a proper state for working the next day. This is sufficiently known by the quantity of froth, and by the brassy scaly crust that swims on the top of the liquor; also when, by blowing or stirring it with the hand, the liquor beneath is green, though the surface appears of a brown blue.

"This vat, of which I have just described the process, and the first I had set, was much longer in coming to a colour than the others, because the heat was too strong the second day; but for this accident, it would have been ready for working two days sooner. It was attended with no other bad consequence; and therefore, as soon as it was in a proper state for working, I dipped at several times 30 or 40 pounds of serge. As the liquor was by this means diminished and weakened, it was necessary in the afternoon to replenish with a fresh mixture, composed of a pound of pot-ash, half an ounce of madder, and a handful of bran. Having boiled this a quarter of an hour, it was put into the vat; which was then stirred, covered, and a few embers put round it. In this manner it may be kept for many days; but when you mean to work it, it should be stirred the preceding evening, and supplied with hot embers.

“ When you would reheat this kind of vat, and repleasish it with indigo, you put into a copper two-thirds of the liquor, now no longer green, but of a brown blue and almost black. When it is ready to boil, the scum on the top should be taken off with a sieve; after which it should be suffered to boil, with the addition of two handfuls of bran, a quarter of a pound of madder, and two pounds of pot-ash. The embers are then taken from under the copper, and a little cold water thrown in to stop the boiling. It is then emptied into the vat, with the addition of a pound of indigo pulverized and dissolved in some of the liquor, as I have said above. The vat being then stirred, covered, and a few hot embers put round it, will be fit for working the next day.

“ When an indigo vat has been reheated several times, it should be emptied out entirely and set anew, because the colour becomes dull: for though heated, and in a proper state for working, the green colour is not so beautiful as at the beginning.

“ I have had several other vats set in the same manner, with a greater or less quantity of indigo; as from one to six pounds, proportionably increasing or diminishing the other ingredients; always, however, putting a pound of pot-ash to a pound of indigo. From other experiments which I have since made, I am convinced that this proportion was not absolutely necessary. I am also persuaded that there are many other methods for the preparation of the indigo vat equally effectual. I shall nevertheless make some observations concerning this vat.

“ Of all those which I have had prepared in this manner, I failed but in one; which was occasioned by neglecting to put hot embers round it on the second day. I added some pulverized arsenic, but without any effect; it would never come to a colour. Red-hot bricks were also thrown into it at several times; the liquor at times became greenish, but never sufficiently. At length, after having to no purpose tried several other means without being able to discover why it did not succeed, and having reheated it several times, I had it thrown out at the fortnight's end.

“ The several other accidents which I met with in the conduct of the indigo vat only retarded the success; so that this operation may be considered as very easy in comparison of the pastel or woad vat. I have indeed made several experiments on each of them, with an intent to shorten the time of the preparation; but for the most part not succeeding, or at least not better than by common practice, it is needless to describe them.

“ The liquor of the indigo vat is not in every respect like that of the pastel. Its surface is a brown blue, covered with coppery scales, and the liquor itself of a fine green. The stuff or woollen which it dyes is green when taken out, and becomes blue immediately afterwards. The same observation has been made with regard to the pastel vat, but it is very singular that the liquor of the latter is not green, though it produces the same effect upon woollen as the other. It is also necessary to observe, that when the liquor of the indigo vat is changed out of the vessel, and too long exposed to the air, it loses its green colour, and at the same time all its qualities;

so that, though it yields a blue colour, it is not permanent.

“ There is likewise a cold preparation of an indigo vat Cold indigo with urine, and it is also worked cold. For this purpose, you take four pounds of indigo powdered, and put it into a gallon of vinegar, leaving it to digest over a slow fire for 24 hours. At the expiration of this time, if it be not perfectly dissolved, it is again pounded in a mortar with the liquor, adding now and then a little urine. You afterwards put into it half a pound of madder, mixing it well by stirring the whole with a stick. When this preparation is finished, you pour it into a cask containing 60 gallons of urine: it is of no consequence whether it be stale or fresh. You mix and stir the whole well together; and this should be repeated morning and evening during the space of eight days, or till the surface of the liquor becomes green when stirred, and produces froth like the common vats. It may be worked immediately without any other preparation than stirring it three or four hours before hand. This kind of vat is extremely convenient; because when it is once prepared, it remains so always till it is entirely exhausted, that is to say, till the indigo has yielded all its colour; hence it may be worked at all times, whereas a common vat must be prepared over night.

“ According as you would have this vat more or less considerable, you augment or diminish the ingredients in proportion to your quantity of indigo: thus for every pound of indigo you always put a quart of vinegar, two ounces of madder, and fifteen gallons of urine. This vat is much sooner prepared in summer than in winter. If you would hasten it, you need only take a little of the liquor, heat it in a copper without suffering it to boil, and afterwards pour it into the vat. This operation is so very simple, that it is almost impossible it should fail.

“ When the indigo is entirely exhausted, the vat may be renewed by dissolving some fresh indigo in vinegar; but you must add madder in proportion to the quantity of indigo, and then pour it into the vat, which should be stirred as at first morning and evening: it will be as good as if it were fresh. This, however, should not be repeated more than four or five times; because the grounds of the madder and indigo would tarnish the liquor, which would consequently render the colour less bright. I must however confess, that as I have not myself experienced this vat, I cannot answer for its success: but the following with urine, which I have seen prepared, dyes woollens a very permanent blue.

“ A pound of indigo was first steeped in a gallon of urine for 24 hours; it was afterwards ground in a large iron mortar with the same urine. When by this means the urine became very blue, it was strained through a fine sieve into a small tub; but the indigo which remained in the sieve was beaten again in the mortar with another gallon of fresh urine, and this was repeated till all the indigo passed through the sieve with the urine. This operation, which continued two hours, being finished, about four o'clock in the evening 62 gallons of urine were put into a copper, which was made very hot, but without boiling; and the scum which rose on the surface of the urine was brushed off the copper with

²⁹ Differences betwixt the indigo and pastel liquors.

³¹ An hot vat with urine.

with a becom. This was frequently repeated till nothing rose but a slight white scum. The urine being thus sufficiently purified and ready to boil, it was thrown into the wooden vat; the prepared indigo was then added, and the vat stirred with a rake, in order that the indigo should incorporate with the urine. Immediately afterwards a mixture, consisting of a gallon of urine, a pound of alum, and a pound of red tartar, was added to the vat; but these were first reduced to a fine powder. The urine was then poured out on it in the mortar, and mixed together till it ceased to ferment. It was then poured into the vat, well stirred, and covered. In this situation it was left all night. The next morning the liquor was very green. This showed that the vat was in a proper state, and that it might have been used; but it was suffered to remain without working, because all that had been hitherto done was only the first preparation of the vat, and the indigo which had been put into it was designed only to nourish and temper the urine. Hence the vat was suffered to rest two days in order to complete the preparation, but covered all the time to prevent it from cooling too fast. It was then managed as follows: A second pound of indigo was beaten with purified urine as above. About four o'clock in the afternoon the whole vat was emptied into the copper: it was then made very hot, but not boiled. It still produced a thick scum, which was taken off; and the liquor, being near boiling, was returned into the vat. The indigo was immediately added, bruised as above, with a pound of alum, a pound of tartar, and two quarts of urine, with the addition of another pound of madder: it was then stirred, close covered, and suffered to remain so all night. The next morning it was in very good order; the liquor being very hot, and of a beautiful green: hence it was evidently in a proper state for dyeing; which was executed in the following manner. The substance to be dyed was woollen fleece.

"This fleece had been well scoured with urine, well washed, and perfectly well drained. Being thus prepared, 30 pounds of it were put into the vat. It was then well opened with the hands, that it might be equally drenched; and after this it was suffered to remain an hour or two according to the degree of shade that was required. During this time the vat was kept close covered, in order to preserve the heat; for the hotter it is, the better it dyes: when it becomes cold, it ceases to act. When the wool was sufficiently blue, it was taken out in large balls, as big as a man's head; and at the same time squeezed and wrung over the vat, and immediately given to four or five women who stood round the vat, in order to open it, and expose it to the air between their hands till the green colour which it had coming out of the vat changed to blue. This change was produced in three or four minutes. These 30 pounds being thus dyed, the vat was raked, and then suffered to stand for two hours, keeping it always close covered. At the expiration of this time they put in another 30 pounds of wool, which was opened well with the hands. The vat was again covered; and in four or five hours this wool had taken as good a colour as the former: it was then taken out of the vat in balls in the same manner as the former. This operation being finished, the vat was still warm,

but not sufficiently so to dye any more wool; for when it has not a sufficient degree of heat, the colour which it yields will be neither uniform nor solid; hence it is necessary to reheat and replenish with indigo as before. This may be done as often as you think proper; because this vat never spoils by age, provided that while it is kept idle you give it a little air.

"About four o'clock in the afternoon all the liquor was emptied into the copper, with the addition of a sufficient quantity of urine to replace what had been evaporated and lost in the preceding work. This generally requires about eight or nine buckets of urine. The copper was then heated, the scum taken off as before: when ready to boil, it was returned into the wooden vat. You add to it a pound of indigo, pounded and mixed with urine as above, a pound of alum, a pound of tartar, a pound of madder, and two quarts of urine. After the vat is stirred and close covered, it is suffered to stand all night. It will be in a proper state the next day, and capable of dyeing 60 pounds of wool at twice, as above. In this manner, the reheatings should be always done the day before you want to dye, and may be repeated ad infinitum.

"It is necessary to observe, that the more indigo you put into the vat at once, the deeper the colour: thus, instead of one pound, you may add four, five, or six, without increasing the quantity of alum, tartar, or madder; but if the vat contains more than three hogsheds, the quantity of the ingredients should be proportionably augmented. That which I have just mentioned contained only three hogsheds, and was consequently too small to dye at one time a sufficient quantity of wool to make a piece of cloth, viz. 55 or 60 pounds. To do this properly, it should contain six hogsheds, which would be attended with a double advantage. First, all the wool might be dyed in two or three hours; whereas, by twice dipping, it could not be finished in less than eight or ten. Secondly, at the expiration of the three hours, the vat would be still very warm; so that, after stirring and letting it settle for a couple of hours, the same wool may be dipped again. By this means the colour is heightened almost as much more; because wool once dyed always takes a much better colour than new or white wool, though suffered to remain in the vat even for 20 hours.

"It is necessary to be very attentive in opening the dyed balls as soon as they are taken out of the vat, and exposing them to the air, in order to change them from green to blue, which should be done by many hands at the same time, that they may be equally affected by the air, else the blue colour will not be uniform.

"Some manufacturers pretend that cloth, the wool of which had been dyed in this urine vat, cannot be perfectly scoured by fulling even at twice; others to the contrary, and I believe they are right, Nevertheless, if the first be right, one would suppose that the animal oil of the urine was become resinous by drying on the wool, or that incorporating with the oil by which the wool had been moistened for its other preparations, it would be more likely to resist the fuller's earth and soap than simple oil by expression. To remedy this, it is only necessary to wash the wool in

in running water after it has been dyed, expressed, and opened, ungreened, and again cold. Be this as it may, a passel vat in a large dye-house is preferable to those kinds of indigo vats prepared with urine; because with a good woad vat and a dexterous woad-man, you expedite more work than could be accomplished with any other blue vat. In mentioning the several indigo vats in this treatise, my design is not so much to introduce them to great manufactories, as to assist those who work at small fabrics; to whom, I flatter myself, this treatise will be equally useful. I will even describe a cold vat for the dyers of small stuffs mixed with thread or cotton, which succeeds very well, but which would be of no use for woollens.

³³ Another cold indigo vat.
"In some places they make use of a cold indigo vat, differing from that already mentioned, which is more commodious, as it is much sooner ready, and has no bad smell. It is prepared in the following manner."

"Three pounds of indigo, well pulverized, is put into a glazed earthen vessel, and dissolved in three pints of soap-boiler's lixivium, which is a strong solution of fossile alkali with quicklime. I have made use of a solution of potashes, and succeeded very well. The solution of indigo is performed in about 24 hours, as may be easily discovered by its remaining suspended in the liquor, which is thereby thickened, and becomes like an extract. At the same time you put into another vessel three pounds of flaked lime sifted with six quarts of water. The whole should boil during a quarter of an hour, and when settled should be drained off clear. You afterwards dissolve in this lime-water three pounds of green copperas, suffering it to settle till the next day. You then put 75 gallons of water into a large deal cask, the only wood proper for the purpose; as any other, particularly oak, would blacken and tarnish the liquor. The two solutions, which had been prepared the night before, are then added, the vat stirred, and left to settle. I have seen it sometimes take the colour in two hours; but with this vat it was very different, not being ready till very late the next day. It produces a great quantity of froth; and the liquor takes a fine green colour, but a little yellowish, something like the green of the common vat."

"When the vat is almost exhausted, it is replenished and quickened without fresh indigo, by adding to it a small liquor, consisting of two pounds of green copperas dissolved in a sufficient quantity of lime-water. But when the colour of the indigo is quite exhausted, it should be replenished with fresh indigo dissolved in a lixivium, such as I have just described. It is natural to suppose, that the quantity of your other ingredients must be augmented or diminished in proportion to the indigo. Some dyers use a mixture of vinegar and water impregnated with rusty iron. They suppose that the colour is thereby rendered more solid; but I am convinced by experience that there is no necessity for it, and that the colour is as permanent as any of the other blues prepared as I have directed above."

"The first time I prepared this vat, I proceeded according to a receipt sent me from Rouen. The soap-boiler's lixivium was simply denominated strong water. I suspected this to proceed either from malice or mistake, nevertheless, as in matters of fact it is unjust

to condemn without examination, I tried the common aqua-fortis, which produced the following effect.

³⁴ "I took half a pound of indigo, well powdered, and effects of steeped it in half a pint of common aqua-fortis, made aqua-fortis with vitriol and salt-petre: this produced a fermentation. In this situation I left it for 24 hours; and having, as in the preceding operation, dissolved a pound of copperas in some lime-water, I poured these two mixtures into a cask containing about 17 gallons of river water. I stirred it well, but there appeared nothing extraordinary the next day. I still continued to stir three times a-day for two days together, and then suffered it to rest for two days more, persuading myself that it was absolutely spoilt. At the expiration of these four days, the liquor became of a red colour, but clearer than the passel vats. I stirred it once more, and let it stand six days longer: it had then a little froth, but very pale: six days afterwards the surface of the liquor became brown, and underneath a brown green. I stirred again, and fancied that the liquor underneath was still reddish, though the froth which it threw up was of a good colour; I therefore conceived hopes that it would do, and that I should be able to work it the next day."

"At the expiration of sixteen hours I dipped some cotton, which took colour, but so very weak, that I was obliged to let it remain in the liquor several hours, till the blue became sufficiently deep. It then withstood the summer air and sun tolerably well for 12 days; nevertheless, I had the vat thrown out as useless, on account of its tedious operation. Doubtless it might have been recovered with lime, or some other alkali that would have absorbed the acid of the aqua-fortis, but it was not worth the pains. Besides, the answer which I received from the person who sent me the receipt from Rouen, contained an explanation with regard to the kind of aqua-fortis that should be used; from which I learnt that it should have been the soap-boiler's lixivium, which, instead of being acid, is one of the most caustic alkalies. In fact, by making use of this alkaline lixivium, the operation was attended with immediate success, and never failed me since."

³⁵ "I tried several of these different vats in miniature, in cucurbits, put into a water or sand bath. These of dyeing blue in last are attended with no difficulty; it is only necessary to diminish the quantity of the liquor, and of every ingredient, in proportion to your vat, and it is scarce possible it should not succeed."

"Concerning that which I first described, and which is set hot, as it is attended with a little more difficulty, and several persons may wish to try this operation themselves, being rather curious, and requiring neither expence nor preparation in miniature; I will give the description of a process which succeeded extremely well, and which I purposely supplied with much more indigo than is generally done in the common method."

"I boiled two quarts of water with two drachms of madder, and four ounces of pearl-ashes. When it had boiled a quarter of an hour, I poured it into a cucurbit, containing about a gallon, which was previously heated with hot water, in which I had put a quarter of a handful of bran. The whole being well stirred with a deal spatula, I put my cucurbit into a very

moderate sand heat, sufficient only to keep it warm, or nearly of the same degree of heat requisite in a common indigo vat.

"I continued the sand heat all night and the next day, without perceiving any alteration. I stirred it only twice during the day with the spatula. The day following it produced an efflorescence, formed a coppery scum on the surface, and the liquor became a brown green. I then filled it with a mixture, composed of a quart of water, two ounces of pearl-ashes, and a little bran. It was well mixed, and then left to settle. It became perfectly well coloured, and the next day I dyed several bits of woollen stuffs. These vats are reheated and replenished with as much case as a great one."

"After having prepared the vats according to any of the methods above mentioned, the dyeing any kind of woollen stuff is exceedingly easy; no other preparation for the dye being requisite than simple immersion in warm water, wringing them, and then dipping them in the vat for a longer or shorter time according to the deepness of the colour you wish to impart. From time to time the stuff should be opened; that is, taken out and wrung over the vat, and exposing it for a minute or two to the air till it becomes blue; for it must be observed, that in all the solutions of indigo or other materials hitherto described, the blue colour is produced by exposure to the air alone, and the stuff is always taken out green, and will retain that colour if not exposed to the air. In dyeing blue, therefore, it is necessary to let the colour change in this manner before you immerse it a second time, that the shade may be the better distinguished; for dark blues require to be dipped several times, but it is dangerous to make this experiment with light blues. When a large quantity of wool is to be dyed, which cannot be put into the vat all at once, it very often happens that the quantity first put in will take up the deepest dye. To prevent this, some dilute their indigo-vat with a quantity of warm water; but M. Hellot disapproves of this, as being apt to produce a fading colour. The best method, he says, is to dip them when the vat is nearly exhausted; and for this purpose he recommends the pastel-vat rather than any other: and though the colours produced in this manner are less bright than the others, they may be sensibly enlivened by passing the stuffs through boiling water. This, he says, is proper for all blue colours; as it not only renders the dye more fixed and bright, but cleanses the stuffs from accidental impurities. After the work is taken out of the hot water, it is to be rinsed in a running stream. It will be still more proper to full a dark blue stuff well with soap and water, and afterwards to rinse it in running water; for the soap will be so far from injuring the colour, that it will thereby be rendered more bright and lively. Some dyers, in order to save the dearer ingredients of pastel or indigo, make use of logwood; but this is by no means allowable, as the colour, though rather brighter than that of indigo, is exceedingly perishable. In 1748, M. Macquer of the Royal Academy of Sciences discovered a method of dyeing silk and cloth with a preparation of Prussian blue, superior to all the blues hitherto discovered. This, however, has never yet come into practice, nor is it at all probable that the colour of this pigment

can ever be made to stand washing with soap. In all the methods in which we could try the experiment, it could not even bear washing with plain water. Indeed, when we consider the great volatility of the colouring matter of Prussian blue, that it can only be fixed by iron, and that any alkaline matter will instantly disengage it, and make it resume its former volatility, there can be but very little hope of overcoming the difficulties which attend the process.

Having been so particular with regard to the preparation of the materials and method of dyeing wool, we need say the less concerning the method of dyeing silk or cotton. The following composition is recommended by M. Macquer. ³⁷ "To eight pounds of the finest indigo add six of the best pearl-ash, from three to four ounces of madder for every pound of ashes, besides eight pounds of bran, washed in several waters to take out the flour. When washed, and most of the water squeezed out, it is placed alone at the bottom of the vat. The pearl ash and the madder are then mixed, bruising them thoroughly together, and then boiling them for a quarter of an hour in a copper containing two thirds of the vat; the liquor is then suffered to rest, and the door of the furnace shut.

"Two or three days previous to this, eight pounds of indigo are steeped in a bucket of warm water, washing it well, and even changing the water, which has a reddish cast. Some begin with boiling the indigo in a ley of one pound of pearl-ash with two buckets of water; after which they pound it while quite wet in a mortar; then while it is yet in a paste, they fill the mortar with hot liquor which has been boiled before; letting it stand to settle for a short time, and then pouring off the clear into a separate boiler or into the vat. The same quantity of the mixture is then poured on the indigo which remained in the mortar, bruising and mixing it well, and then as before pouring it off into the boiler; which operation is repeated till the whole of the indigo is thus dissolved in the liquor. That in the boiler is gradually poured into the vat upon the bran in the bottom, adding afterwards the remainder of the composition, grounds and all. After stirring and raking for some time, it is let stand, but without fire, till it becomes cool enough for the hand to bear. After this a little fire is to be put round the vat, only to preserve the same degree of heat; and this should be continued till the liquor becomes green, which is easily known by trying it with a little white silk. This shows that the vat is in a proper state; but in order to be ascertained of this, it will be necessary from time to time to stir it with a rake, when the brown and coppery scum which appears upon it after standing for a little time shows that it is in a proper state for working. Even in this case it is necessary to behave with the utmost caution, and to observe whether on blowing aside the coppery scum just mentioned a fresh one appears or not; for if it does not, it is a sign that the vat is not yet ready. If the scum appears, it must stand three or four hours, when a new composition is made to complete it. For this purpose as much water as is necessary to fill the vat is put into a copper, boiling it with two pounds of ashes and four ounces of madder as at first. This new liquor is poured into the vat, raked and mixed, and then left to stand for four hours, when it is ready for dyeing.

The method of preparing silk for the blue dye is by boiling with soap, using 35 or 40 pounds of the latter to 100 of the former; but no impregnation with alum is required. Before dipping it in the vat, however, it should be washed from the soap; and to cleanse it more effectually, it ought to be twice beetled at the river, having been divided into hanks for the convenience of wringing. After being dipped in the vat, it is to be wrung as hard as possible, and then opened out to the air, to give it the blue colour, as directed for wool; it should then be immediately washed in two waters, and well wrung out again. Lastly, it is to be dried as quickly as possible; cutting the thread which ties it, if the hanks are large, because if kept tied it frequently turns red under the thread.

Silk dyed as above directed is apt to take the blue very unequally, and will most certainly do so, if not washed and dried immediately after dyeing. Fine dry weather is always best for these operations; for should water accidentally fall upon it, it would be full of reddish spots. In moist weather, therefore, and during the winter, a room with a stove will be necessary. Different shades of blue are produced by dipping that first which is intended for the darkest colour.

The method of dyeing cotton or linen blue is so little different from that already described with regard to woollen or silk, that nothing farther needs be said concerning it; only the colour upon cotton is generally less bright. M. de Apligny indeed tells us, that he has discovered a method of dyeing cotton velvets of a most beautiful and durable blue: but as he does not choose to communicate it, nothing can be said on the subject. In the former edition of this work, a receipt was given for dyeing cotton of a very good blue colour, and which, as being instantaneously done, may occasionally be useful. The indigo is dissolved in a mixture of lime and potash (probably the pure caustic lixivium would answer fully as well); and after it is dissolved, some raisins beat into a pulp in a brass or marble mortar are to be added. This very soon produces a copper-coloured scum at top; and the cotton being now dipped into the liquor receives the colour in an instant. Linen may be dyed in the same manner.

The next of the primitive colours to be considered is red; of which there are many varieties: but the principal are scarlet, crimson, and madder red. The dyeing of these colours differs considerably from that of the blues, because they require a previous preparation in the stuffs to be dyed; and it is on this preparation that the goodness of the colour very often depends. These preparations are generally alum, tartar, aqua-fortis, aqua-regis, or solution of tin in these acids. Galls and alkaline salts are also sometimes added, tho' they do not of themselves contribute any thing to the colour.

There are three kinds of scarlet, viz. that dyed with kermes, with cochineal, and with gum-lac. The first, called Venetian scarlet, is the least bright, but more permanent, and less apt to be spotted than the others; inasmuch that in some pieces of tapestry done with this at Bruxelles in Flanders, it has scarce lost any of its vivacity in 200 years. However, it is scarce ever used except for tapestry, and is dyed in the following manner, according to Mr Heliot.

The wool should be first drenched; for which

purpose you put half a bushel of bran into a copper, with a quantity of water sufficient for 20 pounds of wool, which to the belt of my knowledge is the usual batch for one dyeing. In this liquor it should boil for half an hour, stirring it from time to time; after which it is taken out and drained. I shall observe, once for all, that when you dye worsted, you put a rod through each skein, which commonly weighs about a pound, and which should be kept on the rod during the whole process, by which means the skein is prevented from tangling. It is also convenient for turning the skein, in order to dip each part, that the whole may be equally coloured; for which purpose, you raise it about half way out of the liquor; and holding the rod with one hand, you pull the skein with the other, so as to let the part which before was next the rod fall into the liquor. If the worsted should be too hot for the fingers, it may be done by means of another rod. The equality of the colour depends so entirely upon the frequency of this manœuvre, that it cannot be too strenuously urged. In order to drain them, you rest the ends of the rods just mentioned on two poles; which should be fixed in the wall over the copper.

While the worsted is draining, after being thus drenched, you prepare a fresh liquor, viz. by throwing out what remained in the copper, and replenishing with fresh water; to this you add about a fifth part four water, four pounds of Roman alum grossly pounded, and two pounds of red tartar. As soon as it boils, the worsted on the rods should be immersed for two hours, almost continually moving the rods, one after another, as I have before directed.

It is necessary to observe, that after the alum is put in, when the liquor is ready to boil, it will sometimes rise suddenly out of the copper, if you do not mind to check the boiling by throwing in cold water. If, when it is ready to boil, you put in the cold worsted quickly, it will have the same effect. It is also proper to observe, that when dyers work in the great, they should have their legs bare, that the hot liquor may not rest in the stockings. When the quantity of tartar is rather considerable, as in the present operation, the liquor does not rise so high; but when there is nothing besides the alum, sometimes, when it begins to boil, half of the liquor boils over, unless prevented by the above precautions.

When the worsted has boiled in this liquor for two hours, drained, lightly squeezed, and put into a linen bag, it is deposited in a cool place for five or six days, and sometimes longer; this is called leaving the worsted in the preparation. This delay helps it to penetrate, and increases the action of the salts; for as a part of the liquor constantly evaporates, it is clear that what remains, being more impregnated with the saline particles, becomes more active, that is to say, provided there remains a sufficient degree of moisture; for the salts being once crystallized and dry, their power is destroyed.

When the worsteds have remained in this state for five or six days, they are then in a proper condition for being dyed. A fresh liquor is then prepared, according to the quantity of the worsted; and when it grows warm, if you want a full scarlet, you throw into it 12 ounces of pounded kermes to every pound of worsted; but if the kermes be stale, it will require pound for pound.

pound. When the liquor begins to boil, the worsted should be put in, being still moist; but if it has been suffered to grow dry after boiling, it should be put into warm water, and well drained.

"Before you put the wool into the copper with the kermes, it were advisable to throw in a small handful of refuse wool, which, being boiled for a moment, imbibes a part of the blackness and drofs of the kermes; so that the wool afterwards dyed takes a much more beautiful colour. You now dip the skeins on the rods in the same manner as in the preparation, continually stirring them, and giving them air, from time to time, one after another. In this manner they should be kept boiling for a full hour. They are then washed and drained.

"If you would reap any advantage from the dye still remaining in the liquor, you may dip a little prepared wool, which will take a colour in proportion to the goodness of the kermes, and to the quantity which had been put into the copper.

"If you mean to dye a number of shades, one darker than another, you require much less of the kermes; 7 or 8 pounds being sufficient for 20 pounds of prepared wool. You then dip the quantity of worsted intended for the lightest shade, leaving it in the copper no longer than necessary, in order to turn it, that it may imbibe the colour equally. It is then raised upon the pegs, and the next shade immediately put in, and suffered to remain for a longer time. You proceed in this manner to the last shade, which should also remain till it has acquired the colour you desire.

"You begin with the lightest colour, because if the wool was suffered to remain in the copper longer than necessary, it would be no loss, provided you reserve this batch for the darker shade: whereas, by beginning with the darkest, you would have no remedy in case of any accidental skip in the light shades. The same precaution is necessary in regular shades of all colours; but of the colour in question these are seldom made, because the dark shades are not much in use: and as the operation for all colours is the same, what I have said respecting this will answer for all the rest.

"When the wool has been dyed in this manner, and before it is carried to the river, you may swell it in warm water, with a small quantity of soap, well dissolved; this adds a brightness to the colour; but, at the same time, gives it a little of the rose, that is to say, a crimson tinct.

"In order to render this colour more bright and beautiful than common, I have tried a great number of experiments, but could not obtain a red equal to that produced by cochineal. Of all the liquors for the preparation of wool, that which succeeded the best was made according to the proportions I have mentioned. By changing the natural tinge of the kermes, by various kinds of ingredients, metallic solutions, &c. various colours may be obtained, which I shall presently mention.

"It is impossible to prescribe any proportions for an ell of stuff, considering the infinite variety of their breadth, and even of their thickness, and the quantity of wool in their fabrication; experience is the best guide. Nevertheless, if you chuse to be exact, the surest way is to weigh the stuff to be dyed, and to di-

minish about one quarter of the colouring ingredients prescribed for worsteds; because the stuffs take internally less colour, as their texture, being closer, prevents it from penetrating; whereas the worsted or woollen fleece takes the colour internally as easily as on the exterior surface.

"The alum and tartar, used in the preparation for stuffs, should also be diminished in the same proportion; neither is it necessary to let the stuffs remain in the preparation as long as the worsted: they may be dyed even the day after they had been boiled.

"Woollen fleece dyed in the red of kermes, and to be afterwards incorporated in mixed cloth, or for the manufacture of thick cloths, will have a much finer effect than if dyed with madder.

"A mixture of half kermes and half madder, is called scarlet in half-grain. This mixture gives a colour extremely permanent; but not so lively, inclining rather to a blood colour. It is prepared and worked precisely in the same manner as if kermes alone were used; only that in the liquor they put but half this grain, the other half is supplied by madder. This is consequently much cheaper; and it frequently happens that the dyers who make it, render it much less beautiful than it might be, by diminishing the quantity of the kermes and increasing that of the madder.

"From the trials made on scarlet in grain, or scarlet of kermes, both by exposing it to the sun and by various liquors, it is proved that there does not exist a better nor a more lasting colour. It may for solidity be compared to the blues already mentioned. Nevertheless, the kermes is scarce ever used except at Venice; for since the fiery scarlets are become the taste, this colour is almost entirely exploded. It has, notwithstanding, many advantages over the other, as it neither blackens nor spots; so that should the stuff get greased, the spot may be taken out without impairing the colour. Nevertheless, kermes is so little known to the dyers, that when I wanted a certain quantity for the above experiments, I was obliged to have it from Languedoc; the merchants of Paris encumber themselves with no more than what they vend for the use of medicine."

"The second kind of scarlet, viz. that dyed with cochineal, is much more expensive and less permanent than the other. For inferior uses, such as tapestry, the colour is sometimes partly done with Brasil wood; but this colour cannot be made equally permanent with cochineal: and it is remarkable, that in whatever manner these fugitive colours be mixed with permanent ones, the latter never convey to them any portion of their durability, but, on the contrary, both go off together. The true cochineal scarlet is very difficult to dye in perfection, and almost every dyer has a receipt of his own for the purpose. The success of the whole operation, however, according to Mr Hellot, depends upon the choice of the cochineal, the water used for dyeing, and the method of preparing the solution of tin, which is now universally known to be the only ingredient by which a scarlet colour can certainly be produced. The following is his receipt for the preparation of this liquid, which from his own experience he gives as the best. To eight ounces of spirit of nitre add as much river water, dissolve in the mixture gradually half an ounce of very white sal-ammoniac,

in order to make an aqua regis, to which add two drachms of purified salt-petre. This last ingredient, he owns, might be omitted; but he is persuaded that the use of it contributes to make the colour more uniform. In the liquor thus prepared dissolve an ounce of English tin reduced into grains by dropping it, when melted, into a basin of cold water. These are to be dropped into the liquor one by one, waiting for the dissolution of the first before we add a second, in order to preserve a quantity of red vapours, which are the phlogisticated nitrous acid; and to the mixture of which he supposes the beauty of the colour is partly owing. The solution prepared in this manner is of the colour of solution of gold; and if fine tin be made use of, there is neither black dust nor sediment of any kind to be seen in it; but though transparent when just made, it is apt to become milky with the heats of summer; which, however, is no detriment to it in our author's opinion: and it is certainly just, if the transparency returns with the coolness of the solution. The aquafortis or spirit of nitre used for this purpose ought to be such as will dissolve half its weight of silver: and by following this method you will always be certain of having a composition of an equal strength; so that any slight difference which may arise from the quality of the cochineal will scarce be perceived. A weak solution makes the scarlet incline towards crimson, and a strong one towards orange.

When worsted is to be prepared for the scarlet dye, the following operation is necessary. For every pound of the stuff, ten gallons of clear river water are to be put into a small copper; and when it becomes pretty hot, two ounces of cream of tartar, and a drachm and an half of cochineal, both finely sifted, are to be added. A brisk fire is to be kept up; and when the liquor is ready to boil, two ounces of the composition already described must be added, by which the liquor is immediately changed from crimson to blood colour. As soon as it begins to boil, the worsted, previously steeped in hot water, and then expressed, is to be added. It must be suffered to boil for an hour and an half; after which it is taken out, gently squeezed, and washed in cold water, having taken care to stir it constantly all the time. It will now be a tolerable flesh colour, or even somewhat darker, according to the goodness of the cochineal and the strength of the solution of tin; but the colour will be so totally absorbed by the stuff, that the remaining liquid will be almost as colourless as water. This is called the scarlet boiling; and without this the dye would not hold. To finish the dye there must be another preparation of very clear water, the goodness of this being of the utmost consequence to the goodness of the colour. In this preparation, along with the other ingredients, there must be half an ounce of starch; and when the liquor is pretty hot, six drachms and an half of cochineal, likewise finely powdered, is to be added. A little before it boils, two ounces of the solution of tin are put in; by which, as in the former case, the colour is instantaneously changed. As soon as it begins to bubble, the worsted is to be dipped, allowed to boil an hour and an half, stirring it all the time, and then washing it as already directed. An ounce of cochineal will be sufficient to give a proper

depth of colour to a pound of wool; a drachm or two more might be added, if you would have the colour very deep, but if it be much enlarged, the dye will turn out very dull.

In dyeing the scarlet colour, the material of which the cauldron is made is by no means a matter of small consequence. On this our author has the following observations. "Their cauldrons in Languedoc are made of fine tin. They are also used by several dyers at Paris; but Mr Julienne, whose scarlet is very highly esteemed, makes use of brass cauldrons. These are also used in the dyeing manufactory of St Dennis. Mr Julienne is careful only to suspend a large pack-thread net, with pretty small meshes, in his cauldron, to prevent the stuff from touching. At St Dennis, instead of a net, they use a large open wicker basket; but this is less convenient than the net, because it requires a man at each side of the copper to keep it even, and to prevent it, when loaded with the stuff, from rising to the surface of the liquor.

44
This practice, so different with regard to the materials of the cauldron, determined me to make an experiment. I took two ells of white Sedan cloth, which I dyed in two cauldrons, one of copper, furnished with a pack-thread net, and another of tin. I weighed the cochineal, the composition, and other ingredients, with as much accuracy as possible. They boiled exactly the same time. In short, I was sufficiently attentive to make the operation the same in every particular; that in case of any perceptible difference it could only be attributed to the different materials of the cauldrons. At the first boiling, the two patterns were absolutely alike, except that the piece done in the tin cauldron was rather more marbled, and not quite so even as the other; but this in all probability might be occasioned by their not having been equally cleansed at the mill. I finished each piece in its proper cauldron, and they were both of them very beautiful. Nevertheless, it was very evident that the cloth which had been dyed in the tin was more fiery, and the other rather more crimsoned. They might have been easily brought to the same shade; but this was not my object. From this experiment, it appears that, with a copper cauldron, the quantity of the composition should be increased; but then the cloth grows harsh to the feel. Those who dye in copper, to prevent this evil add a little of the turmeric, which is a drug only used for false colours, and therefore prohibited by the regulations to dyers in grain, but which gives scarlet that dazzling fiery colour so much the fashion at present. It is, however, if you have any suspicion, easy to discover the deception, by cutting the pattern with a pair of scissors. If it has no turmeric, the cut edge will appear white, otherwise it will be yellow. When the close texture is equally dyed with the superficies, let the colour be what it will, they say the colour cuts, and the contrary when the middle of the texture remains white. Legitimate scarlet never cuts. I call it legitimate, and the other false, because that with the addition of the turmeric is more liable to fade. But as the taste for colours is so variable, as the bright scarlets are at present the mode, and as it is necessary, in order to please the buyer, that it should have a yellow cast, it were better to authorise the use of the turmeric, though

a false colour, than to allow too large a quantity of the composition, by which the cloth is injured, being more liable not only to dirt, but also to tear, as the fibres of the wool are rendered brittle by the acid.

"I must also add, that a copper cauldron should be kept extremely clean. I have myself frequently failed in scarlet patterns by neglecting to clean the cauldron. I cannot in this place forbear condemning the practice even of some eminent dyers, who at about six o'clock in the evening make their preparation in a copper cauldron; and, in order to gain time, keep it hot till day-light the next morning, when they dip their stuffs. The preparation must undoubtedly corrode the copper during the night; and consequently, by introducing coppery particles into the cloth, injure the scarlet. They will tell us that they do not put in the composition till immediately before the cloth is dipped: but this is no apology; for the cream of tartar added on the preceding evening being sufficiently acid to corrode the copper, forms a verdigris which dissolves, it is true, as soon as it is formed, but which nevertheless produces the same effect.

"As tin is absolutely necessary in the scarlet dye, it were much better to have a cauldron of this metal, which would infallibly contribute to the beauty of the colour. But the price of these cauldrons, if sufficiently large, is an object of consideration, especially as they may melt in the first operation if not carefully attended to by the workmen. Besides, it would be very difficult to cast a vessel of so large a size without flaws that would require to be filled. It is absolutely necessary that they be made of block tin. If the flaws should be filled with solder, which contains a mixture of lead, many parts of the cauldron will retain the lead, which being corroded by the acid composition will tarnish the scarlet. Hence there are inconveniences in every particular: nevertheless, if it were possible to procure a skilful workman capable of casting a cauldron of the Melac tin without flaw, it were certainly preferable to every other; for though the acid of the composition should in some parts corrode it, the detached particles will do no harm, as I have already observed.

"There is no danger of melting a tin cauldron, but when it is emptied in order to fill it with a fresh liquor. I shall therefore add the precautions necessary to prevent this evil. In the first place, the fire should be taken entirely from the furnace, and the remaining embers quenched with water. Part of the liquor should then be taken out with a bucket, while the remainder should be dashed about with a shovel by another person, in order to keep the upper part of the cauldron continually moist, at the same time cooling what remains in the cauldron with cold water. In this manner it should be continued till you can touch the bottom without being burnt. It should then be entirely emptied, and all the sediment taken up with a moist sponge. This attention will preserve your cauldron.

"Woollens are never dyed scarlet in the fleece, for the two following reasons: The first is, or ought to regard all stuffs of simpy one colour; those of many colours are called mixed stuffs. These kind of stuffs are never dyed in the wool, especially when the colours are bright and fine; because, in the course of the fabrica-

tion, the spinning, twisting, or weaving, it would be almost impossible to prevent some white or other coloured wool from mixing, which though ever so trifling would injure the stuff. For which reason, reds, blues, yellows, greens, or any of those unmixed colours, should not be dyed till after they have been manufactured. The second reason is peculiar to scarlet, or rather to the cochineal, which being heightened by an acid, cannot stand the fulling without losing much of its colour, or being at least excessively crimsoned. For the soap which contains an alkaline salt destroys the vivacity produced by the acids. Hence it is evident that neither cloth nor stuffs should be dyed scarlet till they have been fullled and dressed.

"To dye different pieces of cloth at the same time, the directions already given do not entirely answer.

48
For example, in order to dye five pieces of Car-
cassonne cloth at the same time, each piece five quar-
ters broad, and fifteen or sixteen ells in length, it is
necessary to observe the following proportions: You
begin by making the composition in a very different
manner from the preceding process, viz. twelve pounds
of aquafortis put into a stone jar or glazed vessel, with
twenty-four pounds of water, and one pound and an
half of tin grains added. The solution goes on more
or less slow according to the acidity of the aquafortis,
and should stand for twelve hours at least. During
this time a kind of blackish dirt falls to the bottom;
the top should be then drained off the sediment: this
liquor is of a clear lemon colour, and is preserved by
itself. This process evidently differs from the first by
the quantity of water mixed with the aquafortis, and
by the small portion of tin, of which scarce any re-
mains in the liquor; for the aquafortis not being in
itself a solvent for tin, only corrodes and reduces it to
a calx, provided neither saltpetre nor sal ammoniac be
added, which would convert it into an aqua regia.
The effect of this composition is not, however, different
from others, and is perceptible to those who
from experience are competent judges of this colour.
The composition without sal ammoniac has been for a
long time used by the manufacturers of Carcassonne,
who doubtless imagined that its effect was owing to a
supposed sulphur of tin, and may be preserved from
putrefaction for thirty hours in winter and only twenty-
four in summer. It then grows turbid, forms a
cloud, which falls to the bottom of the vessel in a
white sediment. This sediment is a small portion of
the tin, which was suspended in an acid not prepared
for the solution. The composition, which ought to
be yellow, becomes clear as water; and if employed in
this state never succeeds, but produces the same effect
as if it had been milky.

"When the composition is prepared, as I have now
described, according to M. de Fondieres, you put, for
the quantity of cloth last mentioned, about sixty cubic
feet of water into a large copper; when the water
grows warm, you add a sackful of bran: it is some-
times necessary to use four water; they will either of
them do, as they say, to correct the water, viz. to ab-
sorb the terreous and alkaline substances, which crim-
son the tinge of the cochineal. We should be well
informed concerning the nature of the water employed,
in order to know whether these correctives be neces-
sary.

"Be it as it may, when the water is a little more than warm, you add ten pounds of crystals or cream of tartar pulverised, that is to say, two pounds to each piece of cloth. The liquor should be then violently stirred; and, when rather hot, you should put into it half a pound of the powder of cochineal, mixing it well together, and immediately afterwards you pour into it twenty-seven pounds of the composition, very clear, which also requires to be well stirred. As soon as it begins to boil, the cloth being immersed, should boil very fast for two hours, and during that time should be kept in continued motion on the wynch, and when taken out passing it through the hands by the lifting, in order to open and give it air. It is afterwards carried to the river and well washed.

⁴⁹
Method of stirring the cloth. "In order perfectly to understand the method of stirring the cloth, it is requisite to observe, that a kind of reel or wynch, with a handle for turning, should be placed horizontally on the iron hooks which are fixed in the fellows that support the edge of the cauldron. You first join the several ends of each piece of stuff to be dyed at the same time; and as soon as they are immersed, you carefully keep the end of the first piece in your hand; you then lay it on the reel, which should be turned till the end of the last piece appears. It is then turned the contrary way, and in this manner every piece will be dyed as even as possible.

"When the cloth has been well washed, the cauldron should be emptied, fresh liquor prepared, to which you must add, if necessary, a sack of bran or some four water; but if the quality of the water be very good, there is no occasion for any addition. When the liquor is ready to boil, you put in eight pounds and a quarter of cochineal pulverised and sifted. The whole is then mixed together as even as possible; but when you cease to stir, you must mind when the cochineal rises to the surface, forming a kind of scum of the colour of lees of wine. As soon as this scum begins to divide, you pour in eighteen or twenty pounds of the composition. You should have a vessel full of cold water near the cauldron ready to throw in, lest after putting in the composition it should rise above the edge, as is sometimes the case.

"When the composition is put into the copper, and the whole well mixed, you turn the wynch quick for two or three turns, that every piece may imbibe the cochineal equally. It is then turned more slowly, in order to let the water boil. It should boil very fast for two hours, constantly turning and keeping the cloth down with a stick. The cloth is then taken out, and passed through the hands by the lifting, in order to give it air and to cool it; it is afterwards washed at the river, dried, and dressed.

"There is a considerable advantage in having a great quantity of stuff to dye at the same time; as for example, when the five first pieces are finished there remains a certain quantity of the cochineal, which, supposing seven pounds at first, might amount to twelve ounces; so that cloth put into this second liquor will imbibe the same shade of rose-colour as if you had coloured a fresh liquor with twelve ounces of cochineal. The quantity remaining may, however, vary very much according to the quality of the cochineal, or according to the fineness of the powder. Though the quantity of colour remaining in the liquor may be very in-

considerable, it nevertheless deserves attention on account of the dearth of this drug. Of this liquor, therefore, a preparation may be made for five pieces of cloth; and it will require less of the cochineal and less of the composition, in proportion, as near as you can guess, to the quantity remaining in the liquor. This is also a saving of fuel and time; but it is impossible to give positive directions concerning this manœuvre, which must be left to the ingenuity of the dyer; for having dyed rose-colour after the scarlet, you may make a third preparation, which will dye a flesh-colour. If there is not time to make these two or three preparations in 24 hours, the liquor spoils: some dyers put Roman alum into the liquor to prevent it from spoiling; but this changes it to a crimson.

"Scarlets thus crimsoned in the same liquor in which they had been dyed, are never so bright as those done in a fresh liquor. Drugs which reciprocally destroy each other's effect are more efficacious when employed in succession.

"When you dye cloth of different qualities, or any kind of stuffs, the best method is to weigh them, and for every hundred pound to allow about six pounds of crystals or cream of tartar, eighteen pounds of the composition in the preparation, the same quantity in the completion, and in each of them six pounds and a quarter of cochineal. For the accommodation of those who would make small experiments, the whole may be reduced, viz. one ounce of cream of tartar, six ounces of the composition, and an ounce of cochineal for every pound of stuff. Some of the Paris dyers succeed very well by putting two-thirds of the composition and a quarter of the cochineal in the preparation, and the remaining third of the composition, and the other three-quarters of the cochineal, to the completion.

"It is not the custom to put crystal of tartars in the finish: I am however convinced by experience that it does no harm, provided that at most you put but half the weight of the cochineal; and in my opinion it made the colour rather more permanent. There have been dyers who have dyed scarlet at three times: in this case they had two preparations, and afterwards the finish; but they always used the same quantity of drugs."

We have already observed, that the kermes were so little used for brown or Venetian scarlets, that these kind of colours were made with cochineal. For this purpose the preparation is made as usual; and for the dyeing they add to the liquor eight pounds of alum to every hundred weight of stuff. This alum is dissolved in a separate cauldron with a sufficient quantity of water: it is thrown into the liquor before the cochineal. The remainder is done precisely the same as in common scarlet: it gives the cloth the colour of Venetian scarlet; but it is not by any means so permanent as the colour obtained from kermes.

There are no alkaline salts that do not crimson scarlet; but it is more generally the custom to use alum, because these alkaline salts are no addition to the permanency of the colour, and may possibly injure the stuffs, because all animal substances are dissolved by fixed alkalies. The alum, by being deprived of its phlegm by calcination, will more certainly crimson. The liquor which had been used for crimsoning is red, and

and still redder in proportion as the scarlet is more crimsoned, so that the colours part with much of their basis in the liquor by which they are darkened. It is, however, impossible to darken in grain without salts. The late Mr Barron, in a memoir which he presented to the Royal Academy of Sciences 12 or 15 years ago, remarks, that he succeeded better with the salt of urine, than with any other salt, for uniting the colour and preserving its brightness and fulness; but, as he observed, it is very inconvenient to make any quantity of this salt.

It has been observed, that the choice of the water for dyeing scarlet was of importance; the greatest part of the common waters sadden, because they almost always contain a quantity of stony or calcareous earth, and sometimes of sulphureous or vitriolic acid. These are commonly called hard waters; by this term they mean water that will not dissolve soap, and in which it is not easy to dress vegetables. By absorbing or precipitating these heterogeneous substances, all waters are rendered equally good. If the matter be alkaline, a little sour water will produce this effect. Five or six cubic feet of this sour water, added to 60 or 70 cubic feet of other water before it has boiled, will cause the alkaline earth to rise in a scum which may be easily taken off the liquor. A sackful of any kind of white mucilaginous root cut in small bits, or, if dry, powdered, will also, if the sack be left to soak in the water for a half or three-quarters of an hour, correct a doubtful water; bran, as we have said above, will also answer the same end tolerably well.

The scarlet produced by gum-lac, though less bright than cochineal, has the advantage of being more permanent. The lac most esteemed for dyeing is of a branched form. The colour is that of an animal, like that of cochineal and kermes, and the branched kind has most of the animal particles in it. The best kind is of a blackish brown colour on the outside, and red within; and from some experiments made by M. Geoffroy, it appears to be a kind of comb, somewhat resembling that made by bees or other insects of that kind. Dyers sometimes use it when pulverised, and tied up in a bag; but to this M. Hellot objects, because some of the gum-resin being melted by the heat of the boiling liquid, escapes through the cloth, and adheres to it so closely, that it must be scraped off with a knife when cold. Others endeavour to extract the colour by boiling it in water after it has been reduced to powder, and then letting it stand to settle, and pouring off the coloured liquid; but in this way it often turns putrid. M. Hellot, therefore, after several unsuccessful trials to extract all the colour readily, had recourse at last to mucilaginous roots; which, without communicating any colour of their own, retained that of the lac so effectually as to remain with it upon the filtre. Comfrey-root was that with which he succeeded best. For extracting the colour, he used it dried and powdered, in the proportion of half a drachm to a quart of water. In this it is to be boiled for a quarter of an hour; then strained through a linen cloth, and poured while quite hot upon the gum-lac powdered and sifted through an hair-sieve. By this it immediately acquires a fine crimson colour; after which the whole is set to digest in a moderate heat for twelve hours, stirring the gum which remains at the bottom seven or eight times. The

water thus impregnated with the colour is afterwards decanted into a vessel large enough to contain four times the quantity, which is then to be filled with cold water. A small quantity of strong solution of Roman alum is then added; the coloured mucilage subsides; and if any colour remains in the liquor, it may be precipitated by the addition of some more alum, until at last the water will be left entirely colourless. After the crimson mucilage is entirely sunk to the bottom, the clear water is drawn off with a syphon, and the remainder put upon a filtre, to let the liquid slowly drop off or evaporate. If the whole of the colour be not extracted from the lac by one operation, it is to be repeated till no more appears, and the residuum becomes of a pale straw-colour. The best lac, detached from its branches, does not yield more than one-fifth of its weight in colour; and hence there is no great advantage to be made by substituting it in place of cochineal for the scarlet dye.

For dyeing scarlet with this extract of gum-lac, the Method of requisite quantity of it, dried and powdered, is to be put into an earthen or block-tin vessel. Some hot water is then to be poured upon it; and, when well moistened, add the proper quantity of the scarlet composition, stirring the mixture with a glass pestle. By this means the powder, which before was of a dark dirty purple, acquires an exceedingly bright scarlet. The solution in which the crystals of tartar had been previously dissolved is then to be poured into the liquor; and as soon as the latter begins to boil, the cloth is to be dipped into it, turning it over and over according to the common method. The remainder of the operation is to be performed in the same manner as if cochineal were used. The extract, in our author's opinion, afforded about a ninth part more colour than cochineal.

53
M. Hellot's
method of
extracting
the colour
of gum-lac.

54
Method of
using the
extract of
gum-lac.

55
Of dyeing
crimson.

Crimson is the colour produced by cochineal with alum and tartar only, without any solution of tin. For this colour two ounces and an half of alum, with an ounce and an half of white tartar, are to be taken for every pound of wool. These being put into a cauldron with a proper quantity of water, are to be made to boil before the stuff is put in. As soon as the liquor begins to boil, the wool is to be put into the cauldron, and the boiling continued for two hours; after which it is to be taken out, gently squeezed, rinsed in water, and put into a bag, which is also necessary to be done with the preparations for every other colour. A fresh liquor must be prepared for the dye, in which an ounce of cochineal is to be put for every pound of wool. When it begins to boil, the wool is to be put in, and managed as already directed for scarlet. For the finest crimson, the stuff, after the common process is finished, should be dipped in a new liquor in which a small quantity of sal ammoniac is to be dissolved, and an equal quantity of potash added after it is pretty hot.

A very beautiful crimson is obtained by boiling the wool as for common scarlet, then making a second preparation with two ounces of alum, and an ounce of tartar to every pound of wool. It should remain an hour in this decoction. A fresh liquor is then to be prepared immediately; in which to every pound of wool you put six drachms of cochineal. When it has remained an hour in this liquor, it is taken out and immediately dipped in a solution of barilla and sal ammoniac.

moniac; and in this manner a great number of very beautiful shades of crimson may be prepared by diminishing the quantity of cochineal. In this process it is necessary that the mixture of alkaline salt and sal ammoniac should not be too hot, as this would cause the volatile spirit evaporate too quickly, and the crystals of tartar also, being neutralised, would lose their effect.

56
Of dyeing
silk of a
crimson
colour.

For dyeing silk of a fine crimson with cochineal, M. Macquer recommends only 20 pounds of soap to 100 of silk; because (says he) the little natural yellow still remaining in the silk, after only this quantity of soap, is favourable to the colour.

Having washed and beetled the silk at the river to discharge it well of the soap, it is put into a very strong solution of alum, where it should remain generally from night till the next morning, about seven or eight hours. The silk is then washed and twice beetled at the river; during which time the following liquor is thus prepared:

You fill a long boiler about one-half or two-thirds full of river water; when this water boils, you throw in some white nutgalls pounded, letting it boil a little longer, about a quarter of an ounce to two ounces for every pound of silk. If the nutgalls are well pounded and sifted, they may be put in at the same time with the cochineal.

The silk being washed, beetled, and distributed upon the rods, you throw into the liquor the cochineal, carefully pounded and sifted; it must be then well stirred with a stick, and afterwards boiled. You may put from two to three ounces for every pound of silk, according to the shade required. For the most common crimson colours two ounces and an half is sufficient, it being seldom necessary to use three ounces except for some particular match.

When the cochineal has boiled, you add to the liquor for every pound of cochineal about an ounce of the solution of tin in aqua regia; it is called composition, and made in the following manner:

One pound of the spirit of nitre, two ounces of sal ammoniac, and six ounces of fine tin in grains: the two last are put into an earthen pot of a proper size; twelve ounces of water is then poured on it, the spirit of nitre afterwards added, and the whole left to dissolve.

This composition contains much more tin and sal ammoniac than is used for the scarlet of cochineal on wool; it is however absolutely necessary.

This quantity of the composition should be well mixed and stirred in the liquor, and the copper then filled with cold water, about eight or ten quarts to every pound of fine silk; coarse silk requiring less, as it occupies less space. The liquor is then fit to receive the silk which is immersed, and returned till it appears uniform, generally requiring about five or six returns. The fire is then stirred; and whilst the liquor is boiling, which it should do for two hours, the silk is returned from time to time. The fire is then taken from under the copper, and the silk put to soak in the same manner as for aluming. It should remain for five or six hours, or even, if the liquor be ready at night, till the next morning. It is then taken out, washed at the river, twice beetled, wrung as usual, and put on the perches to dry.

To fadden the grain of scarlets, the silk when taken out of the cochineal liquor is washed and twice beetled at the river; the water-liquor is then prepared, in summer as it is, but in winter a little warmed, adding a solution of copperas, more or less according to the darkness of the shade required. The silk should be returned in this liquor, in small hanks, till it becomes very even; and when the shade is equal to expectation, should be taken out, wrung and put to dry without washing if you like, because the copperas liquor is little more than clean water. The copperas gives the cochineal a violet tinct, depriving it of its yellow. If, however, it should appear to lose too much of its yellow, it may be preserved by adding to the copperas liquor a little of the decoction of fustic. Nothing but copperas will fadden grain scarlets; the logwood being quite useless for this purpose, copperas alone will suffice, as it darkens greatly with the nutgalls used in grain scarlets.

The process just related for producing this colour is the most in use at present, as it gives a more beautiful shade than can be obtained by any other method. Nevertheless, as many dyers proceed in the old way, we shall describe it here.

For these grain scarlets the round paste, as imported from the Indies, is added in the boiling of the silk. When the soap boils, about an ounce of rocou is bruised in the eulender, in the same manner as described for orange-colours. It should be pounded as fine as possible, lest any lumps should remain and stick to the silk.

This small quantity of rocou, in the boiling of the silk, has the same effect as the composition, yellowing a little. The remainder of this process is just the same as the preceding; but without the addition of either composition or tartar.

The silk dyers are accustomed to use only the finest cochineal, and even always prefer the prepared cochineal, which is cleansed from all its impurities, sifted and picked. This is certainly commendable, considering that the cochineal not prepared being less pure, the more of it must be added, and that the dregs remaining in the liquor may injure the colour. The white tartar used in grain scarlets serves to exalt and yellow the colour of the cochineal, producing this effect by its acidity, all acids having the same effect: we must, however, observe, that tartar is preferable, as it gives a more beautiful tinct. But, notwithstanding the quality of the tartar, it is still incapable of exalting the colour of the cochineal sufficiently to produce a grain scarlet, whatever quantity may be added if employed by itself: for if the dose of this ingredient be moderate, it will not yellow enough; and if too large, it destroys and degrades the colour, without any good effect. In order to assist the tartar, it will be necessary to add some of the composition, which, as we have seen, is nothing more than a solution of tin in aqua regia. This solution with cochineal, when used for dyeing of worsted, has a considerable effect, changing it from a crimson, its natural colour, to a prodigious bright fire colour; and produces only a crimson when applied to silk: but it gives this colour a very beautiful tinct; for uniting with the tartar, it augments the effect without impoverishing the colour, saving the rocou ground, as we have before observed.

⁵⁷ "As to nutgalls, they produce no good effect with regard to colour: on the contrary, if you use too much, they tarnish to a degree, entirely spoiling the crimson colour; nevertheless, it is always the custom to put the quantity we have specified.

"One might probably conjecture from the introduction of this practice, that scarlets were formerly produced with cochineal, without either tartar or composition, yellowing only with rocou: silk dyed in this manner, however, would have no rustling, so that it could not be distinguished from silk dyed with Brasil wood. Nutgalls, on account of their concealed acid, having the property of giving the silk a great rustling, are therefore added with cochineal; by which means these scarlets are distinguished by the feel from the scarlet of Brasil wood: for we must observe, that the Brasil dye cannot stand the action of the nutgalls, by which it is entirely destroyed.

"But besides giving this rustling to the silk, it has at the same time the singular and very remarkable quality of adding to its weight very considerably; so that by putting one ounce of nutgalls to every pound of silk, you add two or two and a half per cent. to the weight: by this means some silk-dyers add even seven or eight per cent. They are so much accustomed to this advantage in weight, owing to the nutgalls, that even when this drug becomes useless by the addition of the tartar and composition, which produces the same rustling, they make it still necessary on account of the weight, which is not proportionably increased by the other acids. White nutgalls are always preferable to the black, as they injure the colours much less. We may, however, hence conclude, that for grain scarlets nutgalls are not only useless but very prejudicial; and serving only as an imposition, is a blameable practice, and injurious to commerce.

"The silk is thus suffered to remain in the liquor, in order to make it wholly imbibe the cochineal. During this repose it takes a good half-shade; and the colour yellowing in proportion, gives it a much finer cast.

"One would be apt to believe, that leaving the silk to boil in the liquor for a longer time would have the same effect; but experience proves the contrary: besides, it would be more expensive, considering that it would be necessary to continue the fire.

"The cochineal leaves on the silk, when taken out of the liquor, a kind of scale, or rather the skin of the insect, which always contains a portion of the colouring juice. In order, therefore, to cleanse the silk perfectly from this kind of bran, it is twice beetled when washed at the river. By this means the colour becomes more brilliant, clearer, and fuller.

"The two beetlings before dyeing are necessary, because the silk having been strongly alumed for this colour, and intended to boil in the dyeing liquor for a great while, would, without this precaution, yield a certain quantity of the alum, which not only injures the colour, but likewise prevents the perfect extraction of the cochineal; for generally all neutral salts added to the dyeing liquor have more or less this inconvenience.

"The grain, or cochineal crimson, such as described, is not only a very beautiful, but may be considered as a most excellent colour: it is the most permanent

of all dyes for silk. It perfectly resists the boiling with soap, and evidently suffers no alteration from either the sun or the air. Silk stuffs of this colour, commonly used in furniture, are sooner worn out than faded. It is frequently seen that the colour of this grain crimson in furniture, though more than 60 years old, is scarce impaired. The only observable difference occasioned by time is, that by losing the yellow cast it becomes rather darker, approaching nearer to the violet."

⁵⁸ The dyeing of cotton red is attended with much more difficulty than any of the substances hitherto mentioned; and indeed to produce a good scarlet or crimson upon it has hitherto been a desideratum in the art. The following are M. Apligny's directions for dyeing such reds as are commonly in use. "It is necessary, previous to the dyeing of cotton thread, to cleanse it from that unctuous matter by which the dye is prevented from penetrating its pores. For this purpose they make use of four waters; which is prepared by throwing some handfuls of bran into hot water, and letting it stand 24 hours, or till the water becomes four, when it is fit for use. These four waters, however, cleanse the cotton but very imperfectly, carrying off only the superficial part of the unctuous matter, which river water would do as well. The lixiviums of ashes are more effectual; and therefore all fixed alkalies, particularly kelp, or even the ashes of new wood, are, for the reason I have already given, generally preferred for this operation. The salts are extracted in the same manner as by the bleachers; and the cotton is then steeped in these lixiviums, which, like the silk, is inclosed in a clean linen pocket or sack, to prevent the skeins from tangling: it should boil for a couple of hours: when perfectly cleansed, the pockets sink to the bottom of the liquor, because the impeding matter being removed, the water penetrates the pores. The pocket is then taken out of the copper, the skeins separated from each other, and washed at the river. They are afterwards wrung on the peg, and again rinsed till the water comes off clear. The skeins are then spread on the perches to dry.

"To dye cotton red requires three preparations, viz. cleansing, galling, and aluming. The operation of cleansing as above.

"With regard to the galling, any kind of galls may be used in case of necessity; or even tan may be substituted; but that requiring more, it would not answer the purpose so well. The black Aleppo galls, because less suffices, are preferable to the white galls, which though cheaper make the expence come nearly equal. The Aleppo galls are, however, liable to dull the colour, which though easily revived, the white not producing this inconvenience, are generally preferred by most dyers. It requires nearly five quarts of liquor to drench one pound of cotton; so that for 20 pounds, five pounds of pounded galls are boiled in about 120 quarts of water; it should boil for two hours, or till by pressing it between the fingers it breaks easily.

This liquor is drawn off clear, and poured into a tub, into which, when cold, or even whilst warm, the cotton, which was before divided into hanks of about eight ounces each, and tied with a thread to prevent them from tangling, is dipped. Suppose, for example, that having about 40 of these hanks, and 100 quarts of the gall liquor, a part of it necessarily evaporating

rating in the boiling, five quarts of this liquor is taken out of the tub and put into a trough, into which you dip two skeins at once, carefully working them till they are soaked. They are then taken out and laid in an empty tub, pouring over them the remainder of the liquor in which they had been soaked: five quarts more are then taken out of the tub containing the gall water, poured into the trough, and two more hanks dipped into it, and so on successively till the whole is galled. The gall liquor should be stirred in the tub every time you take out, that the whole of the cotton may be galled equally, which it would not be were the grounds to settle at the bottom. This operation finished; if any of the liquor remains, it is poured on the galled cotton, being orderly ranged in the tub; where, after remaining 24 hours, it is taken out skein by skein, gently wrung, and then put to dry.

"The aluming for the cotton consists of about four ounces of Roman alum for every pound of the substance. Having pounded the proper quantity of alum, it is dissolved over the fire in a copper containing a sufficient quantity of water, taking care not to let it boil, otherwise it would lose its strength. The liquor is immediately poured into a tub or trough of cold water, proportioned to the quantity of the cotton, so as that the whole of the liquor may be as that of the galling, 100 quarts for every 20 pounds of cotton. It is the custom to add to this alum liquor a solution partly composed of arsenic and white tartar, with one part of the lixivium of kelp. The first solution consists of one grain of arsenic and two grains of white tartar, in two or three quarts of water. When the water in the copper boils, the arsenic and tartar, well pounded, is put into it, and kept boiling till the liquor is reduced to about half. When cold, it is strained and put into bottles or vessels, which should be stopped and kept for use.

"The kelp lixivium is made with about half a pound to a quart of water. You will know if this lixivium be sufficiently strong, when by putting an egg into it the point only appears on the surface.

"You then add to the alum liquor for this supposed 20 pounds of cotton 20 quarts of the solution, and three quarts of the said lixivium, observing nevertheless that the whole of the water used in mixing the alum and other substances be always in the proportion of five quarts of liquor to every pound of cotton. The 20 pounds of cotton are then plunged into this aftringent pound by pound, in the same manner and with the same precaution as in galling; it is afterwards wrung, but without being too much squeezed, and then slowly dried.

"Some dyers never use the solution of tartar and arsenic with the alum, rationally supposing that these substances, as they rust and yellow the red colours, would be prejudicial to the dye: the red furnished by madder, being already too much inclined to this shade, requires rather to be faddened; and for this reason partly the kelp lixivium is added to the aluming. Several, therefore, use six quarts of this lixivium instead of three; and these six quarts containing the salts of about three pounds of kelp, which by supposing the kelp ashes to contain a quarter of its weight of salt, is in proportion of half an ounce to every quarter of a pound of alum.

"Instead of the solution of tartar and arsenic, others

make use of a solution of sugar of lead, prepared separately. It should be observed in this particular, that when the sugar of lead is dissolved in common water, it becomes turbid and whitish, because plain water not dissolving this perfectly, a kind of partial separation of the calx of lead takes place; but by mixing a sufficient quantity of distilled vinegar with the water, the calx entirely disappears and the solution is complete.

"When the cotton is taken out of the aftringent, it is lightly wrung on the peg, and dried. The more slowly it dries, and the longer before it is maddered, the brighter the colour. Twenty pounds of cotton are generally dyed at the same time; but it were still more advantageous to dye only 10, because when there are two many hanks to work in the copper, it is very difficult to dye them equally, the hanks first immersed having time to take a great deal of colour before the last are put in; for as the first cannot be returned upside down till after the last are plunged, it is morally impossible that the dye should be even.

"The copper in which this ten pounds of cotton are dyed should contain about 240 quarts of water,—that is, 20 quarts of water for every pound of cotton; its shape should be an oblong square, and about two feet deep. It should also be wider at top than at bottom; the difference, however, should not be too great, because in that case the hanks laid flanking on the sides would be liable to spot. As several dyers have erred for want of knowing how much water the copper should contain respecting its dimensions, and as the greater part of the braffers are likewise ignorant in this particular, it may not be amiss, in this place, to add a short and easy method of finding the contents of a vessel.

"In the first place, suppose the vessel round or cylindrical, you begin by measuring the diameter; you then seek the circumference, afterwards the surface; and at last, by multiplying the surface by the perpendicular height, the product is the cube sought for, and determines the contents of the vessel.

"For example, a copper 22 inches deep by 30 diameter; to find the surface, take the proportion of the diameter to the circumference, which is as 7 to 22: state as in the Rule-of-Three, the first number 7, the second 22, and the third 30; the fourth number will be the circumference. This fourth number is found by multiplying the two middle numbers, 22 and 30, by each other, and dividing the product 660 by 7, the first number; the quotient 94 is the circumference sought for. If a square or oblong vessel, as in the present case, you have the circumference by adding the length of the four sides.

"Multiply afterwards the half of the circumference by the radius, that is 47 by 15, the product 705 is the number of square inches, and consequently the surface of your vessel.

"At last multiply 705 by 22, which is the perpendicular height, the product 15510 is the number of cubic inches your vessel contains. If it is larger at top than at bottom, it is necessary, in order to determine the circumference, to take a middle number between the breadth of the top and the breadth of the bottom, as if the copper be 33 inches at the top and at bottom 27, the middle number and real diameter is 30.

"Having multiplied the surface by the perpendicular height, you must reduce the inches to feet. Now the

the square foot being equal to 144 square inches, and the cubic foot to 1728 cubic inches; you must therefore in this example divide 15510 by 1728, the quotient $9\backslash frac\{1\}\{4\}$ will be about the number of cubic feet in the copper; and as a cubic foot contains 35 quarts, consequently the copper contains 318 quarts Paris measure. (The Paris pint is our quart.) To madder 10 pounds of cotton, a copper containing 248 quarts of water is made hot. When it is rather too hot for the hand, six pounds and a quarter of good Dutch grape madder is put into it, and carefully opened and diffused in the liquor. When it is well mixed, the cotton, which had been previously passed on the rods and suspended on the edge of the cotton, is dipped into it hank by hank. When it is all dipped, the hanks on each rod are worked and successively turned upside down, beginning from the first that was put in, and so proceeding to the last; returning to the first, and thus continuing without intermission for three quarters of an hour, always maintaining an equal degree of heat, but without boiling. The cotton is then raised and drawn out upon the edge of the copper, and about a pint of the kelp lixivium poured into the liquor. The rods are then passed through the threads by which each hank is bound, and the cotton put back into the copper and boiled for about 12 or 15 minutes, keeping it entirely immersed during that time. It is at last raised, gently drained, wrung, washed at the river, and wrung a second time on the peg.

"Two days afterwards the cotton is a second time maddered, about eight ounces of madder to every pound; that is, five pounds of madder added to the dyeing liquor. The cotton is then worked in it in the same manner as in the first maddering, with this difference, that none of the lixivium is added, and that the liquor is made of well-water. This maddering being finished, and the cotton cooled, it is washed, wrung, and dried.

"To brighten this red, you put into a copper or trough a quantity of warm water sufficient to drench the cotton, pouring into it about a pint of the lixivium. In this liquor you immerse the cotton pound by pound; leaving it in for an instant only, when it is taken out, wrung, and dried.

"On this operation it ought to be observed, that the method of dyeing in two liquors has no advantage. For, besides that it consumes more time and wood, the second maddering cannot furnish much dye, considering that the alstringent salts are exhausted by the boiling of the first maddering; consequently that the cotton, when deprived of these salts, cannot take the dye. I propose therefore another method now pursued with success by several dyers: it consists in giving the cotton two aluminings, and afterwards dyeing in one liquor only. By this means it takes the dye much better, and acquires more depth, because the whole of the madder turns to advantage. With respect to brightening, it is a needless operation for red cotton destined for the fabrication of callico; because the colour is brightened after it is woven, by dipping in warm water sharpened with a little of the lixivium. When the cotton is taken out of this water, if washed at the river and spread on the grass, the red brightens much better than by any other operation.

"The reds hitherto mentioned are vulgarly called
N^o 106.

madder reds, though those I am going to describe are equally obtained from a species of madder coming from the Levant. The latter, however, commonly called lixary, furnishes a dye incomparably finer than that produced by the best Zealand madder: it is, however, the fashion to call the red of madder the first dye, and the Adrianople red the second. The process of the latter I shall give in this place.

"When you have 100 pounds of cotton to dye, you put 150 pounds of Alicant soda, inclosed in clean linen, into a tub. This tub should be full of holes at the bottom, that the liquor may run into another tub underneath. The 150 pounds of soda being in the upper tub, is covered with 300 quarts of river-water, measured by wooden pails containing each 25 quarts. The water that passes from the first tub into the second is again poured over the soda at different times, till it has extracted all the salt. This lixivium may be tried with oil: if it uniformly whitens, and mixes well with the oil without any appearance of separation at the surface, it is then sufficiently saturated with the salt. It may be also tried with a fresh egg, as I have said above. You again pour 300 quarts of water over the soda contained in the superior tub, in order to extract the whole of the salt. Two similar lixiviums are afterwards made, each with the same quantity of water as had been used for the soda, viz. 150 pounds of fresh wood-ashes, and the other with 75 pounds of quicklime. These three lixiviums being clarified, 100 pounds of cotton are put into a tub, and watered with each of these lixiviums in equal proportion. When it has perfectly imbibed these salts, it is put into a copper full of water without being wrung, and boiled for three hours: it is afterwards taken out and washed in running water. This operation being finished, the cotton is dried in the air.

"A quantity of the above-mentioned lixiviums is then poured into a tub in equal portions, so as to make 400 quarts. In a part of this liquor, 25 pounds of sheep's dung, with some of the intestine liquor, is well diluted by means of a wooden pestle, and the whole strained through a hair-sieve. Twelve pounds and a half of good olive-oil poured into this mixture, when finished, instantly forms a soapy liquor. In this the cotton should be dipped, hank by hank, stirring every time, and with the same precautions I have already recommended in the aluming of cottons destined for the madder red. The cotton having remained 12 hours in this soapy water, is then taken out, lightly wrung and dried. This operation is repeated three times. The liquor that runs from the cotton when wrung falling again into the trough where the cotton was laid is called sickion, and should be kept for brightening.

"When the cotton has been three times dipped in this soapy water, and afterwards dried, it is again dipped three times in another composition, made in the same manner as the first, with 400 quarts of lixivium and 12$\backslash frac\{1\}\{2\}$ pounds of oil, but without the sheep's dung: the remainder of this liquor is also preserved for brightening. The cotton having been dipped in this liquor three times with the same precautions, and left in it the above-mentioned time, it is then carefully washed at the river to divert it entirely of the oil, without which the aluming would not take effect. Having been washed,

washed, it should be as white as if it had been bleached.

“ When dry, you proceed in the aluming, which is done twice successively; but it is needless to give a detail of what has been sufficiently explained in the article upon madder red. It is enough in this place to say, that the galls, about a quarter of a pound to every pound of cotton, should be pulverized; that six ounces of alum should be put to the first aluming; for the second four ounces; and at last, that an equal quantity of the lixivium be added to the alum-water. We must also observe, that it were best to make an interval of three or four days between each aluming; and that no other astringent be added, all metallic salts being in general injurious to the beauty of the colour.

“ Some days after the last aluming, you proceed to dyeing in the same manner as above, only using two pounds of lizary in powder for every pound of cotton; and, before you dye, adding to the liquor about 20 pounds of liquid sheep's blood. It should be well struck into the liquor, which should be carefully skimmed.

“ In order to brighten the colour, the cotton is dipped in a lixivium of fresh wood ashes, dissolving in it five pounds of the best white Marfeilles soap; the water should be warm before the soap is put into it. In this mixture the 100 pounds of dyed cotton is immersed, and worked till it becomes perfectly penetrated. Six hundred quarts of water are then put into another copper; and when warm, the cotton, without squeezing it out of the first, is put into the second, and boiled for three, four, five, or six hours, over a very slow fire, but as equal as possible, carefully covering the liquor to keep in the vapour, that none may escape but what passes through a funnel of small reeds.

“ Some pieces of the cotton are taken out from time to time; and when sufficiently revived and washed thoroughly, the red is perfect. The cotton may be also brightened in the following manner: when washed and dried immediately after dyeing, it should be soaked in the sickiou for an hour, well squeezed, and also dried. When dry, you dissolve for every 100 pounds of cotton 5 pounds of soap in a quantity of water sufficient to cover the cotton. When the water is warm, the cotton is immersed; and having well imbibed, is put into a copper with 600 quarts of water. The whole is boiled very slowly during four or five hours, keeping the copper covered to prevent the steam from going off. This second method makes the red much brighter than the finest Adrianople car-nation.

“ The process just described was practised at Dar-netal, and in other manufactories of France, according to instructions communicated by a person who had seen this process in Turkey. But whether his observations were inaccurate, whether he concealed a part of the mystery, or whether the success of the operation depended on the concurring circumstances accompanying the various mixtures, I know not. Few, however, by closely observing this process, have hitherto obtained a red either so permanent or so beautiful as the red of Adrianople, and those who have succeeded think it but just to reap the advantage of their secret.

VOL. VI. Part I.

On this subject, however, several not unuseful reflections may be advanced.

“ First, the manner of purging the cotton indicates that this process is capable of damaging considerably, and of rendering the cotton very brittle, owing to the sharpness of the lixivium in which it is steeped, so burning in its nature as to make holes in the legs of the workmen who tread it with their feet. It is therefore more simple and less dangerous to cleanse the cotton in six quarts of lixivium to every pound of substance, and containing only six ounces of kelp for every six quarts; to boil the skeins in it afterwards, inclosed in clean linen pockets.

“ By this method the cotton would be sufficiently cleansed without being spoiled; the kelp may be even reduced to half the quantity, substituting in its place double its weight of fresh wood ashes, which would answer quite as well.

“ Secondly, that the failure of many dyers is owing to their not sufficiently divesting the cotton of the oil, which prevents both the galling and aluming from taking effect. The mixture of the lixivium and oil not being well made, or the lixivium being too weak, the oil forms with it but an imperfect combination. This oil therefore, separating and swimming on the surface of the lixivium, sticks to the cotton, which it greases, and by obstructing the pores prevents the gall from penetrating. Great attention therefore should be given to the lixivium, in order to extract all the salt of the kelp, and to use quicklime, which is absolutely necessary to render this lixivium caustic; a quality without which the oil cannot possibly form a combination with the alkali, consequently can make no soap.

“ In Europe the oil of olives is substituted instead of the oil of sesamum, which is used in the East-Indies and in Turkey; but the nature of these oils makes no difference in the operation. The oil of sesamum differs from the oil of olives only because it is thicker, consequently nearer to the nature of animal fat or wax; but the conclusion resulting from this difference is, that less of it may be required than of the oil of olives. Were the oil of sesamum absolutely necessary, it might have been easily procured. The sesamum is a species of fox-glove that grows in the Indies; but is cultivated in Italy, and especially in Sicily, where it is called giurgulena. The same kind of oil may be obtained from plants analogous; such as the gratiole the henbane, &c. but the plant whose seed resembles it most is the convolvulus or lizeron.

“ It is certain that the process brought from Adrianople might be greatly abridged; but we must leave the secret to those to whom it belongs: and I am besides convinced, that a memoir on this subject will be presented to the Academy of Sciences, and therefore will not anticipate.

“ With regard to the sheep's dung and intestinal liquor, it is of no use in fixing the colour. But we know, that these substances contain a large quantity of volatile alkali quite developed, which has the property of rosing the red colours. If the bones of animals owe to their tenacious gluten the faculty of retaining so strongly the madder colour, the vivacity of this colour may be attributed, as from experience we

D d

learn,

learn, to their volatile alkali. It were absurd to imagine that the Europeans only had discovered this phenomenon; as it may be rationally supposed, that the Indians, having perceived it by accident, sought to imitate what chance had brought to their knowledge. It is certain, that in the red dye of the Maroquins, the process of which was brought from the Levant, they prepared the goat skins for dyeing with dog's excrement, having found it effective in exalting the dye of the lac.

"In the dyeing of cotton thread, it is common to mix the sheep's dung with a lixivium of fixed alkali; by which the volatile principle of the dung is retained, and consequently putrefaction prevented. By dipping the cotton several times in this soapy liquor, it is impregnated with the predominating alkaline principle; and we know by experience, that substances once impregnated with volatile alkali, for example, chemical vessels used in extracting it for a long time, retain a smell very like the smell of musk, even after having been well scrubbed with sand, ashes, soap, &c. Every time the cotton is dried when taken out of this liquor, the evaporation of the aqueous particles (the alkaline principles being changed into earth) produces a stronger adhesion in the pores of the cotton. From the union of this earth with a portion of the oil employed, a mastic is the result, which is afterwards completed by the alum; and this, in a word, is the theory of the fixity of this colour.

"Linen thread may be dyed in the same manner; only that, previous to its being purged like the cotton thread, it is usual to boil it in water, adding for every pound of thread a quarter of a pound of chopped forrel. Oil of vitriol is, however, more convenient and better than forrel. But I refer my reader to what I have already said upon the article of thread; observing only, that by this process the linen thread always takes less dye than the cotton, owing to the difference of their pores.

The following processes were taken from the manuscripts of M. Hellot. "According to the letters of M. Grange, correspondent of the Royal Society, who died at Shiraz in Persia, June 1737, the dyers of the city of Damas dyed their crimson colour, so beautiful and so much esteemed in the east, in the following manner: Take ten rottes (a rotte weighs five pounds) of silk in skeins; wash it well in warm water; then let it soak in a sufficient quantity of hot water during half an hour; squeeze out the water; dip it afterwards, but once only, in a hot lixivium, made with a sufficient quantity of water, half a rotte of kelp ashes for every rotte of silk, which is immediately drained on rods, taking care not to leave the silk longer in the lixivium than is necessary for its being well soaked, lest the alkali should corrode it.

"Whilst the silk drains, they prepare another liquor cold, with ten ounces of the pulp of yellow melon, very ripe, which is uniformly diffused in a sufficient quantity of water. They steep in this liquor the ten rottes of silk for twenty-four hours; they increase or diminish the quantity of the above drugs in proportion to the quantity of the silk to be dyed. The silk having remained one day in this melon liquor, is several times washed in fresh water till it becomes perfectly

clean; they then hang it to dry. Mean while the workmen fill a large pan of water, adding a half rotte of alum powdered for every rotte of silk. The pan is then suspended over a hot furnace, and the liquor boiled during twenty minutes; after which the fire is taken from the furnace. The silk is then dipped in this alum solution, moderately hot, and again taken out as soon as it is perfectly wet. They then put it into another pan, pouring over it the alum solution, in which it remains four or five hours, but no longer. It is then taken out and several times washed in fresh water.

"Whilst the silk is washing, a workman fills a large pan with water, adding an ounce of baifonge (a fungus), finely powdered, for every rotte of silk; when this new decoction has boiled for half an hour, they add ten ounces of oudex (cochineal), very finely powdered, for every rotte of silk; that is, six pounds four ounces of cochineal for ten rottes of silk. As soon as this cochineal is added, the fire is taken from the furnace. The liquor is then gently stirred round with a stick; and when the mixture is perfectly made, they pour gently and by inclination a little fresh water into the middle of the pan. The water thus added not only cools the dye, but makes it much more lively. They then immediately dip the silk four or five times, wringing after every dip. This tincture is afterwards boiled again for about a quarter of an hour, and the fire is then taken from the furnace as before. When the liquor is a little cool they dip the silk, still observing to wring after every dip. This done, they put the silk into an empty kettle, pouring over it the remainder of the dye, in which it is left to soak for twenty-four hours. It is then well washed in clean water, dried in the shade, and when very dry wove into stuffs. This crimson is much superior to all the French and Italian crimsons; because the silk was never boiled in the dye.

"The dyers of Damas and Diarbequir say, that they could not accomplish this dye without the pulp of the yellow melon in the preparation, or without the baifonge used with the cochineal in the dye. According to M. Grainge, we have this melon in France; but he doubts concerning the baifonge, which is a species of fungus growing on trees in some parts of Persia, from whence it is brought to Damas, and might also be sent into France by the way of Aleppo, were we desirous of imitating this excellence in the crimson dye.

"To avoid mistakes in the quantity of the different ingredients employed in this process, it may be necessary to repeat, that a rotte of silk weighs five French pounds, and that the ten rottes of silk, produced as an example in this memoir, should also serve as a standard with regard to the quantities of the other ingredients.

"As to the water necessary for the preparation of the silk with the kelp, melon, and the alum for the dye, it requires no more than a sufficient quantity for wetting the silk, namely, about a finger's breadth over it, differing from the tincture, which as the skeins are dipped in this liquor at least ten or a dozen times, should be fuller in the kettle.

"The kali used in the preparation of the silk is nothing more than the ashes of a plant called by the Arabs

Arabs kailou. These are preferable to the ashes made from the rouquet, or those made in Egypt.

“The frames used for these silks are similar to the frames used at Lyons.

“At Genoa the silks designed for crimson are boiled in a much less quantity of soap than those intended for any other colour, 18 or 20 pounds serving for a hundred pounds of silk in the crimson dye; for any other colour, the Genoese use 40 or 50.

“When the silk is boiled, it is dipped in the alum liquor; and to a quantity of raw silk, weighing 72 pounds, they put from 16 to 18 pounds of roch alum, finely powdered, into a copper full of cold water. When the alum is perfectly dissolved, the silk is put to soak in it for near four hours: it may remain longer without any inconvenience, silk intended for crimson requiring more alum than for any other colour. When taken out of the alum liquor, it is shook and dressed on the pegs, but without wringing. One of the dyers being questioned why the silk was not wrung when taken out of the liquor? answered, that it would purge it too much from an impregnation so absolutely necessary for its taking the crimson dye.

“Of the 72 pounds of silk already mentioned, 32 pounds is organzine, and the remaining woof. At Genoa it is the custom to allow two ounces of cochineal to twelve of organzine, if designed for the warp of damask furniture, and for the same silk an ounce and three quarters of cochineal for 12 ounces of the woof, supposing it necessary to the beauty of the silk that the warp should be fuller than the woof; and to bring the colour of the damask to still more perfection, they add to the organzine a quarter of an ounce of cochineal, that is, instead of two ounces they add two ounces and a quarter, adding no more to the woof than one ounce and three quarters.

“As the above 32 pounds of organzine should be of the finest colour, they allow two ounces and a quarter of cochineal to every pound of silk; so that upon the whole they use 142 ounces of cochineal, or 11 pounds 10 ounces, Genoa weight; namely, 32 pounds of organzine to two ounces and a quarter of cochineal, making 72 ounces; 40 pounds of woof to one ounce and three quarters, making 70 ounces. Total, 142 ounces.

“In order to dye this 72 pounds of silk, alumed as above, they make use of an oval copper containing when full 200 quarts of water; they fill this copper two-thirds full of clean fountain water, adding afterwards the following drugs pounded and sifted. Two ounces of tartar, two ounces of saffranum, and two pounds and a half of the Levant galls.

“They wait till the drugs have boiled two minutes in this liquor; after which they add the 11 pounds 10 ounces of cochineal finely powdered and sifted; and whilst one of the workmen by degrees makes it sink to the bottom, another keeps violently stirring the liquor with a stick to promote the solution.

“This done, they fill the vessel with clean water to about a foot of the edge, immediately afterwards dipping the 32 pounds of organzine, divided on 14 rods. They let it remain till the vessel which they fill with clean water, and under which they put a large

fire, is ready to boil; they then, to make the silk take the colour more evenly, raise the rods without ceasing, one after another, that each may alternately reach the bottom of the copper, which being but two-thirds full, the upper part of the silk would else remain out of the liquor, the rods being supported on the edge of the copper.

“When the liquor was ready to boil, the forty pounds of woof, divided on 18 rods, were dipped; they still continuing to raise the rods, one after another, for half an hour, both the organzine and the woof, that each may alternately reach the bottom; so that when the workman came to the last he returned to the first, and so on successively.

“After the first half hour, they stopped for a quarter of an hour between every operation, the workmen still raising the rods from the first to the last, five or six times repeated in the space of an hour and an half; all the time keeping a good fire under the copper. The organzine was then steeped in this liquor two hours and a quarter, and the woof only two hours. The fire was then taken from under the copper; and the workman taking out one dip of the organzine and another of the woof, he wrung and dried them as much as he could to see if the colour was what he wished; if not sufficiently deep for the purpose, he let them both remain in the liquor something less than half an hour whilst the liquor was growing cold. He then took out all the silk, wrung it on the peg, then washed it several times in clean water, changing the water every time. This done he wrung it again on the pegs, and so finished the operation.

“It must be observed with regard to the organzine and woof, that though dyed in the same liquor, they were not however of the same shade at the conclusion of the operation; the organzine was deeper, having been a quarter of an hour longer in the cochineal liquor, during which time it was impregnated with the more subtle colouring particles of the cochineal.

“At Genoa it is not the custom to wash the silk out of the cochineal with soap water; on the contrary, they are persuaded that this practice dulls the brightness of the colour, and that the water, both for the cochineal liquor and for washing afterwards, should be the finest spring-water: for they remark, that the crimson dyed in summer with cistern water, is by no means so bright as the crimsons dyed at other seasons when the fountains are full.

“According to the dyers of Genoa, there is a kind of cochineal which though apparently beautiful, is not so in effect; that in using this cochineal it is necessary to alum the silk as much as possible, and to add to it more tartar than before mentioned. It is, however, impossible to give any certain rules concerning this matter; the dyer himself will judge of the quality of the cochineal fit for use. He should however use the best; for were it even a fact that the inferior kind, with the assistance of a greater quantity of alum and tartar, gives a colour equal to the best, the silk thus weakened by alum would necessarily be always less perfect. The Genoese manufacturers are so well convinced of this, that they themselves furnish their dyers with cochineal in proportion to the silk given to be dyed.”

After the operations of dyeing scarlet and crimson already mentioned, there always remains a brown sediment in the bottom of the liquor, which is thrown out as useless. This, on being examined by M. Hellot, was found to be a precipitated calx of tin, as he has ascertained by reviving the metal from it, though not without great trouble, so that there can be no advantage in repeating his experiments. The remainder of this sediment was composed of the dregs of the cream of tartar united with the gross animal particles of the cochineal. These last being washed over with water, and thus separated from the earthy and metallic parts, were dried separately, and afterwards bruised with an equal weight of crystals of tartar; after which they were ground to an impalpable powder, and boiled with a little alum. Thus they communicated a fine crimson colour to a pattern of white cloth; from which our author is of opinion, that the custom of reducing cochineal to powder and only lifting it, does not give an opportunity of sufficiently extracting the colour from this valuable material; he therefore gives the following receipt for doing so in a more perfect manner.

To an ounce of cochineal powdered and sifted as usual, he adds a fourth part of its weight of very white, clean, and dry cream of tartar. These being ground together on a marble stone to an impalpable powder, are used both in the preparation and in the dye, omitting the small quantity of crystals of tartar formerly directed for the preparation. The quantity here directed to be put to the cochineal, he thinks, evidently renders the colour more fixed.

For madder red the preparation is pretty much the same as for kermes, and is always made with alum and tartar. Dyers are not agreed with regard to the proportions. M. Hellot puts five ounces of alum and one of red tartar to every pound of worsted; adding likewise about a twelfth part of four water, and boiling the wool in this solution for two hours. Worsted is to be kept for seven or eight days moist with this solution; but cloth is finished in four days. A fresh liquor is prepared for dyeing this wool; and when the water is sufficiently hot to bear the hand in it, you must throw in, for every pound of wool, half a pound of the finest madder, carefully stirring and mixing it well in the copper before you put in the wool, which is to be kept in for an hour; but without letting it boil, as that would tarnish the colour. Nevertheless, for the dyer's security, it may boil for three or four minutes at the end of the operation; but the more that madder is boiled, the worse is the colour it yields.

The third primitive colour spoken of among dyers is that of yellow: and for this M. Hellot observes, that there are ten different ingredients fit for the purpose, though only five of them yield a good and permanent dye. These are weld, savory, green-wood, yellow-wood, and fenugreek.

Weld or wold generally yields the truest yellow, and is therefore preferred to all the others. Savory and green-wood, being naturally greenish, are the best for the preparation of wool to be dyed green; the two others yield different shades of yellow.

The shades of yellow, best known in the art of dyeing, are straw colour, pale yellow, lemon colour, and full yellow. The common orange colours are not

simple, and therefore we shall not speak of them at present.

68
For dyeing worsted and stuffs yellow, you make use of the usual preparation, viz. of tartar and alum. You allow four ounces of alum to every pound of wool, or 25 pounds to every 100. With regard to the tartar, one ounce to every pound is sufficient for yellow, though it requires two for red. The method of boiling is similar to the preceding. For the welding, that is to say for yellowing, when the wool or stuff has boiled, you make a fresh liquor, allowing five or six pounds of weld to every pound of stuff; some inclose the weld in a clean woolen bag to prevent it from mixing in the stuff; and to keep the bag down in the copper they put on it a cross of heavy wood. Others boil it in the liquor till it has communicated all its colour, and till it falls to the bottom; the stuff is then suspended in the net, which falls into the liquor; but others, when it has boiled, take out the weld with a rake, and throw it away. They sometimes mix yellow wood with this weld; and some dyers mix any of the other ingredients before specified, according to the shade required. By varying the proportions of the salts for the preparation, the quantity of the colouring ingredients, and the time of boiling, it is possible to produce an infinite variety of shades.

For regular shades of light yellows you proceed as for all other regular shades, only that light yellows require a weaker preparation. For example, 12 pounds and a half of alum to 100 pounds of wool is sufficient. The tartar should also be diminished, because the wool is always washed a little by the preparation, and that when you require only light shades they may be as easily obtained by a weaker preparation; thus you save also in the expence of the salts. But these light shades do not so well stand the test as the darker shades, which are dyed with the full proportion of tartar. Some dyers suppose that by letting their wool and stuff remain longer in the dye, they remedy this evil; because they imbibe the colour more slowly in proportion to the weakness of the decoction: if you put wool into the dye, differently prepared, it will in the same time imbibe different shades. These weaker preparations are called half preparations or quarter preparations, and require great attention, especially for light shades of wool when dyed in the fleece for the manufacture of cloth and mist stuffs, because the wool is harder and more difficult to spin in proportion to the quantity of alum in the preparation; the stuff is consequently less fine. This observation is not, however, of much importance with regard to worsteds for tapestry, neither with respect to stuffs; but it is not much amiss were it only to show that the quantities of the ingredients used in the preparation are not so very exact; but that they may be varied without any risk, whether to give to the same shades to wool prepared in different preparations, or whether to make but one preparation, if more convenient for different shades.

In order to dye with yellow wood, it should be split, or rather shaved with a joiner's plane: by this means it is more divided, consequently yields better, so that a smaller quantity will do. Prepare it as you will, it should always be tied up in a bag, to prevent it from mixing with the wool, and from tearing the stuff.

stuff. The savory and green-wood, when used instead of weld, in order to vary the shade, should be inclosed in the same manner.

"To the above mentioned ingredients for dyeing yellow we may here add the root of dock, the bark of ash, especially the second bark; the leaves of the almond tree, peach, and pear tree; in short, all astringent leaves, barks, and woods. These will produce good yellows, more or less fine according to the time they have boiled, and in proportion as the alum or tartar predominates in the preparation. A larger quantity of alum makes it almost as fine as the yellow of weld; if the tartar prevails, the yellow has more of the orange; but if these roots, barks, or leaves, boil too much, the yellow terminates in shades of fawn colour.

"Though several dyers are accustomed for the good dye to use turmeric, a root imported from the East Indies, and which produces an orange yellow, it is however blamable; because the colour very soon fades, at least if not fixed with marine salt, as practised by some dyers who carefully conceal this art. Those who use it for common scarlet, in order to give cochineal, and to give a lively orange red, are also reprehensible; for scarlets dyed in this manner very soon lose their bright orange cast, which darkens by the air. We are, however, obliged in some degree to tolerate the deception; for this flaming colour being so much in vogue, it were impossible to produce it otherwise but by increasing the quantity of composition, the superabundant acid of which considerably injures the cloth."

69
To dye silk of a yellow colour.

For dyeing silk of this colour it should have about 20 pounds of soap for every 100 of stuff; and after boiling with this ingredient, it should be washed, alumed, and washed again (which is called refreshing), when it is to be put upon the rods in hanks of about seven or eight ounces, and then dipped and returned in the yellow liquor. The finest yellow for silk is weld; and the process, as delivered by M. Macquer, is as follows:

"A copper is prepared with about two pounds of weld to every pound of silk; and that all the weld may be well soaked, it is loaded with a large piece of wood. When it has boiled a good quarter of an hour, the bunches are pushed to the far end of the copper, or rather, if you please, taken out; and by means of a bucket or ladle all the liquor may be taken out of the copper, and strained into a copper or wooden trough; that is, by putting a sieve or linen cloth across a trough; by which means the liquor is cleared from all the grain and little straws left by the weld in boiling. The liquor thus strained is left to cool till you can bear your hand in it: the silk is then dipped and returned till the colour becomes uniform. If this boiling does not make sufficient to fill the trough, it must be supplied with water, which should be added before the liquor is cold, that the degree of heat already mentioned may be preserved. In general, all dying vessels should be full, that the silk when dipped may be only two inches from the edge.

"During this operation the weld is a second time boiled in fresh water; and when it has boiled, the silk should be raised at one end of the trough, either up-

on a kind of barrow, or upon the edge of the trough. Half the liquor is then thrown away and replenished by adding of the second boiling as much as was taken from the first, observing to rake and mix the liquor well: such is generally the method when any new addition is made; at least if the contrary is not particularly specified. This new liquor may be used rather hotter than the first; it should nevertheless be always of a moderate heat, because otherwise it would destroy a part of the colour which the silk had already taken, probably owing to the silk being deprived of part of the alum by the heat of the liquor. The silk is returned in this fresh liquor as at first; mean while you prepare a solution of pearl-ash in proportion of about one pound to every twenty pounds of silk.

"For this purpose the pearl-ash is put into a copper, and the second liquor, quite boiling, poured on it, stirring in order to assist the dissolving of the salt. This small liquor is left to subside, and the silk is a second time raised on the barrow or trough, throwing into the liquor about two or three ladles of the clear part of the solution. The liquor is then well raked, the silk replunged, and again returned. This alkali develops and brightens the yellow of the weld. After seven or eight returns, one hank is wrung to try if the colour be full enough and sufficiently bright; if deficient, a little more of the solution of the ashes must be added, and the remainder of the silk done in the same manner till it has taken the shade required. The lixivium, separately prepared, may be added, if you will, at the same time with the second boiling of the weld-liquor; care should be taken however that the liquor be not too hot. This operation is only for yellows, nor would the liquor do for greens.

"For yellow still fuller, approaching to jonquil, when the pearl-ash is added, it may be also necessary to add some rocon, in proportion to the shade required.

"For the light shades, such as pale lemon or Canary-bird, they should be boiled in the same manner as for blues, these shades bring much more beautiful and transparent when dipped in a clear ground. To do this, when the weld is ready to boil, some of the liquor should be taken out and mixed with a little clean water and a little of the liquor of the vat if boiled without azure. The silk is then dipped as usual; and if deficient in shade, the weld liquor must be re-added, and the dipping repeated, if necessary, to complete the shade required.

"For deeper lemon colours the weld should boil as for yellows, adding only a certain quantity with clean water, according to the fulness of the shade required; some of the liquor of the vat may also be added if necessary; but these dark lemon colours may be boiled in the common way as for yellows. It must be observed, however, that the blue of the vat is never added to these colours but when it is intended to give them a greenish cast.

"These very pale yellow shades are rather difficult, as they are very frequently liable to be affected by the air, and to deepen too much while drying. This happens when alumed in the common way, which is too much; but this inconvenience may be avoided, if in-
stead

stead of aluming as for other yellows, a separate liquor is prepared, or even without any particular preparation, only a little alum put into the liquor of the weld.

"In manufactories where they cannot easily procure weld, they make use of the grains of Avignon, and precisely in the same manner; but it gives a less permanent colour."

⁷⁰
To dye cotton yellow. Cotton to be dyed of a yellow colour should be first well cleansed in a lixivium of fresh wood ashes, and afterwards well washed and dried. Another liquor is then prepared by dissolving in the water, when ready to boil, about a quarter the weight of the substance to be dyed of Roman alum. The skeins are plunged into this alum liquor, returning them on the rods for some minutes. When equally penetrated throughout, the threads by which the skeins are tied being passed on the rods, the hanks are laid on the trough containing the alum liquor. The copper or trough is then covered, it being sufficient to keep the liquor hot without boiling. The cotton, having been thus infused for 24 hours, is then dried, but without washing. We must observe, that the longer it remains dry, the better it takes the colour, and that the washing may be even dispensed with previous to the yellow dye.

A strong weld liquor is afterwards prepared, adding for every pound of the substance to be dyed a pound and a quarter of weld. The cotton or thread, having been previously alumed, is then immersed; the boiling checked with cold water, and the substance worked till it has taken the shade required.

The whole when dyed is plunged into a very hot liquor, but not boiling, made of blue vitriol, a quarter of a pound for every pound of the substance. When it has remained for about an hour and an half, the whole, without washing, is thrown into another liquor composed of about a quarter of a pound of white soap for every pound of the substance. Having been well worked and the threads opened, it should boil for three hours or more if you think proper. The soap might be diminished to half the quantity, but the full proportion does better. This operation finished, the whole is well washed and dried.

If you desire a dark or jonquil yellow, neither the linen nor cotton should be alumed; but for every pound of thread should be added two pounds and a half of weld. When it has been dipped and well worked in this liquor till it has taken the colour equally, it is raised above the liquor, and half a pint of the kelp lixivium poured into it, made as directed in the article upon red. The thread is then returned upon the rods, dipped in this liquor; where having remained for a full quarter of an hour, it is taken out, wrung, and dried.

The lemon yellow is done after the same manner, only that for every pound of thread you put but one pound of weld, diminishing the verdigris in proportion, or even omitting it entirely by substituting in its place the alum liquor. By this means the yellow shade may be varied ad infinitum, and without any difficulty; in brightening and fixing the colour, however, the above method must be always observed.

Cotton-velvet is dyed with the root of a plant called careum or terra marita, a species of ruff which comes

from the East Indies. It gives a beautiful yellow colour; but if dyed in the common manner, has but little solidity. This colour, according to M. de Apligny, may be fixed upon cotton or linen thread by dipping them in a solution of sulphur of antimony in the kelp lixivium already mentioned. When treated in this manner, it is very beautiful as well as permanent.

⁷¹
The fourth primitive colour so called among the dyers, is that which bears the appellation of fawn or root colour. It is however a kind of brown, and has the name of root-colour from being an ingredient in a great number of others. The process for dyeing it is different from those lately described; the wool requiring no other preparation than that of being soaked in water, as already directed for blue. The materials for dyeing it are the green shell of the walnut, the root of the walnut tree, the bark of the alder, fantal, fumach, roudoul or fovic, and foot.

The green shells of the walnut, collected when the nuts are perfectly ripe, and put into tubs or casks, and afterwards filled with water, are in this manner preserved till the year following. The shells are also used before the nuts are ripe; but these should be saved apart, in order to be first used; because, as the soft shell which adheres putrifies, it will keep but for two months only.

The fantal or faunders is a hard wood imported from the Indies, generally ground into a very fine powder, and preserved in bags; because it is supposed to ferment, by which it is thought to be greatly improved; but our author has never observed any difference. This ground wood is generally used with one third of cariatour wood; by which, in the opinion of those who prepare it for sale, it is much improved. It is however nothing like so good as the walnut shells; because, if used in too large a quantity, it stiffens considerably, and thereby injures the wool; hence it were best not to use it, either for wool or fine stuffs, except in the lighter shades, where it would not have so bad effect. It is generally mixed with galls, alder bark, and fumach, as by this means only you can obtain its colour when not mixed with the cariatour. It yields but very little with the preparation of alum and tartar, especially if it be not chipped; but notwithstanding these defects, it is used on account of the solidity of its colour, which is naturally a yellow red brown. The air makes it deeper, and soap lighter. It loses but little by a trial of alum, and still less by tartar.

Of all the ingredients for dyeing fawn colours the walnut rind is the best. Its shades are finer, its colour solid; and by making the wool flexible, renders it less difficult to work. It is prepared in the following manner. You fill a cauldron half full of water, and when it grows warm, you add rinds in proportion to the quantity of stuffs to be dyed and to the colour required. It is then boiled; and when it is boiled for a quarter of an hour, the stuffs, having been previously moistened with warm water, are dipped; they are then turned and well stirred, till they have imbibed the colour desired. If for worsteds, requiring an exact assortment of shades, you put less walnut rinds, and begin with the lightest shades. You put more walnut rinds in proportion as the colour is exhausted, and then dip the darkest shades. With regard to stuffs, you

generally begin with the deepest, and as the colour of the dye diminishes, you dip the lightest. They are aired as usual, dried, and dressed.

The root of the walnut tree is, next to the husk, the best dye for fawn colour: it also gives a very great number of shades, nearly resembling those of the husks; hence they may be substituted for each other, but the root requires a different process. You fill your cauldron three quarters full of river water, putting in the root, cut small, in proportion to the quantity of wool to be dyed, and to the shade required. When it is very hot, you dip the wool or stuff, turning and returning it as before, remembering to air it from time to time; and, if stuff, to draw it through the hands in order to shake off the small bits of the root, which might else spot the stuff. To avoid these spots, the root should be tied in a bag. You afterwards dip the lighter stuffs, and so on, till the colour of the root is exhausted. If worked, you always begin with the lightest, as for other colours; but of all things you must be careful to keep your liquor from boiling at the beginning, as in that case the first piece of stuff would imbibe all the colour.

72
Precautions
to be used
in dyeing
with roots.

The method of dyeing with roots is not very easy; for if you are not very attentive to the degree of heat, to turning and returning the stuffs or workeds, so as to dip them equally, you run a risk of their being either too dark or spotted, for which there is no remedy. In this case, the only resource is to dye them marone, prune, or coffee colour. In order to avoid this evil, you must keep the stuffs continually turning on the reel, and dip them only piece by piece, nor let the liquor boil till the root has yielded all its colour. The workeds or stuffs dyed in this manner, should be aired, well washed, and dried.

Nothing more can be said concerning the bark of alder, than what has been already observed with respect to the root of the walnut tree, only that letting it boil at the beginning is not of so much consequence, because it yields its colour less freely. It is generally used for workeds and colours darkened with copperas. It nevertheless produces a good effect on wool not intended for colours extremely dark, and perfectly withstands the power of the air and sun.

Sumach is nearly of the same nature, and used in the same manner as the husks: its colour is not so deep, and is rather greenish. It is for dark colours frequently substituted for nut galls; but a greater quantity is requisite. Its colour is also perfectly solid and permanent. These different substances are sometimes mixed together; and as they are equally good, and produce nearly the same effect, there is no great difficulty in obtaining certain shades. We must, nevertheless, be directed by custom in the production of these fawn colour shades, which absolutely depend upon the eye, and which are not difficult to manage.

With regard to the mixing of these ingredients with ground santal, you put four pounds of the latter into the copper, half a pound of nut galls pounded, twelve pounds of alder bark, and ten pounds of sumach (these quantities will dye 25 or 27 ells of cloth). The whole is boiled; and having checked the boiling with a little cold water, you immerse the cloth, turning and refreshing it for two hours: it is then taken out, aired,

and washed in the river. You afterwards dip some more stuff in the same decoction, if you want a lighter shade; and in this manner you may contrive as long as the liquor retains any colour. The quantities of these ingredients are augmented or diminished in proportion to the depth of the shade required, letting the wool or stuff boil accordingly.

Here we shall describe also the manner of dyeing 73 with foot, though it has less solidity than the others, with foot, and has also the property of hardening the wool, and giving the stuff a very disagreeable smell.

The foot and water is generally put into the copper at the same time, and the whole well boiled. The stuff is then immersed, and more or less boiled according to the shade required; it is afterwards taken out and cooled, and those intended for the lightest shade are then put in; they are afterwards well washed and dried. But the best method is to boil the foot in the water for two hours, to let it stand afterwards, and then to empty the liquor into another copper, without mixing the foot. The wool and stuffs are then dipped in the liquor, and are thereby less hardened than if they had been mixed with the foot: but this does not render the colour more permanent; and indeed it were better never to make use of this ingredient, except for stuffs of little value, especially as it can be supplied by other ingredients already mentioned, and which give a better and more lasting colour, and are besides more softening to the wool. In the dye they frequently employ the green walnut shell, and the root of the walnut tree for their fawn colours. These two substances are useful both for the greater and lesser dye: there are, however, places where it is difficult to meet with them, and where they are therefore obliged to make use of saunders and even of foot.

The last of the primitive colours so called by the 74 dyers, is black; which includes a vast number of black shades, from the lightest grey or pearl-colour to the deepest black. Hence it is ranked among the primitive colours in dyeing; for among dyers the word primitive does not denote simplicity, but only being the original colour from whence a number of others are derived. In order to dye woollen stuffs of a good black, they should first be dyed of a mazarine blue as deep as possible; which is called the basis or ground, and is to be performed in the manner already directed. The stuff ought to be washed well in running water as soon as it comes out of the vat; and afterwards scoured at the fulling mill; which operation is of the utmost consequence, because without it the subsequent colour will be greatly injured by the lime in the liquor for dyeing blue. This being done, the colour is finished in the following manner. For 100 pounds of cloth put into a cauldron of a moderate size, ten pounds of logwood, cut into chips, and ten pounds of Aleppo galls pulverised, the whole enclosed in a bag: these ingredients are boiled in a sufficient quantity of water for 12 hours. A third part of this liquor is emptied into another cauldron, with two pounds of verdigris; the stuff is then entered and turned for two hours without ceasing. It is necessary to observe that this liquor should boil very slowly, or it is still better to keep it very hot without boiling. The stuff is then taken out, and the second third of the liquor thrown into the copper to the first third, with the

addition of eight pounds of copperas. The fire under the cauldron is diminished, and the copperas left to dissolve for half an hour, letting the liquor cool, after which the stuff is kept turning an hour; it is then taken out and cooled. The rest of the liquor is then mixed with the two first thirds, carefully squeezing the bag well. To this is added 15 or 20 pounds of fumach: you give it another boil, and then cool it with a little water; having previously added two pounds more of copperas, you again turn the stuff for two hours; it is then taken out, cooled, and again put into the cauldron, turning it constantly for an hour longer. After this it is carried to the river, well washed and scoured at the fulling mill. When it is thoroughly scoured, and the water comes out of it clear, you prepare a fresh liquor with as much weld as you think proper; you give it one boil, cool it, and dip the stuff. This last decoction softens and confirms it a very fine black. For the most part, however, they do not take so much pains; but are satisfied, when the cloth is blue, to dip it in a decoction of nutgalls, and to let it boil for two hours. It is afterwards washed, and some copperas and logwood added to the liquor; after which the stuff is again dipped for two hours, and then washed and scoured.

It may be also dyed in the following manner: for 15 cts of cloth, previously dyed blue, M. Hellot had a pound and a half of yellow wood, five pounds of logwood, and 10 pounds of fumach, put into a cauldron. In this the cloth boiled for three hours; after which it was taken out, and 10 pounds of copperas thrown into the copper. When the copperas was dissolved and the liquor cooled, the cloth was put into it for two hours; it was then taken out and cooled, after which it was again immersed for an hour, and then washed and scoured: it was tolerably fine, but not so velvety as the preceding.

It was commanded by the ancient French regulations, that stuffs should be maddered after they had been blued, and before they were dyed black. Desirous of ascertaining the advantage resulting from this process, our author took a bit of cloth which had been dyed blue; this being divided, one half was boiled with alum and tartar, and afterwards maddered. It was then blackened in the same liquor with the other half which had not been maddered, conformable to the first of the two methods just described. They were each of them a very beautiful black; it nevertheless appeared that the maddered stuff had a reddish cast: the other black was certainly more beautiful, more velvety, and much finer. There is, indeed, less danger of the maddered stuffs soiling the hands and linen, because the alum and tartar of the preparation had carried off all the loose particles. This advantage is not however sufficient to make amends for the inconvenience of maddering, as the stuff is always in some degree injured by the alum and tartar, and as the madder gives it a reddish cast disagreeable to the eye, and besides this operation raises the price of the dye to no purpose.

Some dyers, to avoid these inconveniences in part, madder their cloth without having previously boiled it in alum and tartar. But madder used in this manner has no permanency.

Black is sometimes dyed without having given it the blue ground; and this method of dyeing is used for light or thin stuffs of inferior value, consequently not considerable enough to bear the expense of a deep blue previous to their being dyed black. It is however proper at the same time to give these stuffs a ground of the green walnut shell, or of the root of the walnut-tree, to avoid the necessity of blackening them with too great a quantity of copperas.

This process is attended with no manner of difficulty. The cloth is prepared with the green walnut shell, and afterwards blackened in the manner already described, or as near it as possible. For with black, as with scarlet, most dyers suppose that they are possessed of a secret for dyeing a much finer black than any of their fraternity; this, however, consists in augmenting or diminishing the quantities of the same ingredients, or in substituting others which produce the same effect. M. Hellot has tried several methods; but supposes that what is strictly meant by succeeding to perfection, depends rather on the manner of working, handling, and airing the stuff properly, than upon the exact quantity of the ingredients.

It may not in this place be improper to explain the ⁷⁶reason of the necessity of giving stuffs a blue, or at least necessary a root colour ground, previous to their being dyed ^previously black; and why the dyeing white black is expressly ^{to dye the} prohibited in France; because in that case it is necessary ^{stuffs blue,} to use a much greater quantity of nutgalls: this would indeed be no great evil, as nutgalls of themselves do not injure the wool; but in order to overcome this gall, according to the workmen's phrase, that is, to blacken it, or properly speaking rather to form an ink on the stuff, it requires a greater quantity of copperas, which not only hardens the stuff, but, from the acidity impressed on the fibres of the wool by this salt, makes it brittle: on the contrary, when the stuff has had a ground, that is to say, a strong layer of some deep colour, there is much less occasion for either.

Blue is preferable to any other colour; first, because it is the nearest to black, which is in fact only a deep blue; and, secondly, as there is no occasion for any other preparation than previously boiling the wool, the stuff is in no respect injured. For the same reason, viz. the preservation of the wool, the root colour is substituted for inferior stuffs instead of the blue, which would enhance the price; it is therefore necessary that this root-colour ground should be as deep as possible; because the darker it is, there is occasion for less copperas to complete the black.

It also frequently happens, that when stuffs of any colour are badly dyed or spotted, they are dipped in black: it is however advisable to dip them first in blue, unless the colour be very dark, in which case they would take a very fine black; but this is the last resource. These stuffs are not commonly dyed black, if it be possible to make them any other colour; because, having been prepared with alum and tartar for the first colour, the copperas requisite for the black would considerably injure and greatly diminish their quality.

The shades of black are greys, from the darkest to ⁷⁷the lightest. They are of great use in the art of dye-^{How to} dye grey ^dyed as well for their own colours simply as when ap-^colours, plied

plied to other colours, which is called darkening. At present we shall mention two methods of producing them. The first and most general is to boil some pounded nutgalls with a proper quantity of water for two hours; at the same time dissolving some copperas in a little water separately. Having prepared a cauldron of liquor sufficient for the quantity of wool or stuff to be dyed, you add to it, whilst the water is too hot for your hand, a little of the decoction of the nutgalls with the solution of copperas. The stuff intended for the lightest grey is then dipped. When sufficiently coloured according to your desire, you add some fresh decoction of nutgalls with some of the infusion of the copperas, and then dip the next shade. In this manner you proceed to the darkest shade, constantly adding these liquors, from the tawny grey even to black; but it is much better to give the tawny grey and the extreme dark shades a blue ground, more or less as you like, for the reason above mentioned.

The second method of producing grey seems to be preferable; because the juice of the galls is better incorporated with the wool, and you are thereby sure of using no more copperas than is absolutely necessary. It even appears that the greys are more beautiful and the wool brighter. It also appears to be equally solid; for they are both of them equally proof against the air and sun. The second method is much less prejudicial to the quality of the wool, and is attended with no more difficulty than the first.

You boil a sufficient quantity of nutgalls, well pounded and inclosed in a clean linen bag; you afterwards put the wool or stuff into this liquor, letting it boil for an hour, moving and stirring it about, after which it is taken out. You then add to the same liquor a little copperas dissolved in a part of the solution, and then dip the woollens intended for the lightest shade. You again add a little of the copperas solution, continuing in this manner as in the first operation till you come to the darkest shades. In either process, if not restrained by patterns, you may catch the precise shades, beginning with the dark and finishing with the light, in proportion as the liquor becomes exhausted of its ingredients; keeping the pieces of stuff or wool immersed for a longer or shorter time, till the stuff takes the colour desired.

It is as impossible to determine the quantity of water necessary for these operations, as it is to specify the quantity of the ingredients, or the time for letting the wool remain in the liquor. The eye must judge of these things. If the liquor be strongly impregnated with colour, the wool will imbibe the shade in a short time; but, on the contrary, it must remain longer if the liquor be exhausted. When the wool is not dark enough, it is dipped a second time, a third, or even more, till it is of a sufficient colour; the only necessary attention is to prevent the water from boiling. If it be by chance too deep, the only remedy is to dip the stuff in a fresh warm liquor, adding to it a little of the decoction of nutgalls. This liquor carries off a part of the precipitated iron of the copperas; consequently the wool or stuff becomes lighter.

But the best way is to take it out of the liquor from time to time, not leaving it in long enough to imbibe

more of the colour than required. It may also be dipped in a solution of soap or alum; but these correctives destroy a great part of the colour, so that it is often necessary to darken it again; by this means the wool, which suffers greatly by the reiterated action of these ingredients, is injured. All greys, however dyed, should be well washed in a large stream, and the darkest even scoured with soap.

These dingy shades, from the lightest to the darkest, are produced by the same operation from which common ink is obtained. The green vitriol contains iron; were it blue, it would contain copper. Pour a solution of this green copperas into a glass, holding it in the light and dropping into it some of the decoction of nutgalls. The first drops that fall into this limpid solution of ferruginous salt produces a reddish colour, the next turns it bluish, then a dusky violet colour, and at last it becomes a dark blue, almost black, which is called ink. To this ink add a quantity of pure water; let the vessel rest for several days, and the liquor by degrees becomes clearer and clearer, till it is almost as limpid as common water, and at the bottom of the vessel you will perceive a black powder. Having dried this powder, put it into a crucible; calcine this, and put to it a little fat or any other fat, you will obtain a black powder which may be attracted by the loadstone. This, therefore, is iron; this is the metal which blackens the ink; and this, when precipitated by the nutgalls, lodges in the pores of the fibres of the wool, dilated by the heat of the liquor, and contracted when the stuff is exposed to the air. Besides the hygroscopic quality of the nutgalls, by which they have eminently the property of precipitating the iron of the copperas and producing ink, they also contain a portion of gum, as may be ascertained by evaporating the filtered decoction. This gum being introduced into the pores with the ferruginous atoms serves to retain them; but this gum being easily soluble, it has not the tenacity procured from a salt more difficult of solution; therefore these dark colours have not the solidity of other solid colours prepared in a boiling solution of alum and tartar, and therefore plain greys have not been submitted to the usual trial.

It is by no means easy to produce a good black colour on silk, though the basis is undoubtedly the dye silk of same, viz. iron dissolved by acids, and precipitated a black colour on the cloth by a vegetable astringent. The following process is given by M. Macquer. "Twenty quarts of vinegar are put into a trough with one pound of black nutgalls pounded and sifted, and five pounds of fresh iron-filings. While the infusion is making, you clean out the copper in which you put the black ground, with the following drugs pounded, viz.

"These several drugs are put into a copper, containing half the quantity of the vessel used for the black ground, and filled with water. Twenty pounds of Campeachy or logwood chips are afterwards inclosed in a linen bag, for the convenience of taking them out

of the liquor, unless you choose to take them out with a pierced ladle, or any other means, because these must boil a second time as well as the other drugs.

"When the logwood has boiled for about a quarter of an hour, it is then taken out and properly preserved. The above-mentioned drugs are then put into the logwood decoction, and also boiled for about a quarter of an hour, carefully checking with cold water as often as it seems ready to boil over.

"This operation being finished, the liquor is strained through a linen strainer into a trough, and then left to settle, carefully preserving the grounds which must be again boiled.

"The cold infusion of the vinegar with the nutgalls and iron filings is then put into the copper intended for the black ground. The fire is afterwards put under it, and the following ingredients immediately added, viz.

These several drugs should be pounded and sifted, except the gum arabic, which is only broken.

"Instead of gum arabic the native gums may be used, and dissolved in the following manner: Some of the logwood decoction is put into a boiler; when hot, you put into it a copper strainer, made in the shape of an egg, and open at the largest end. The gum is put into this strainer, and dissolves as the liquor heats; it must be stirred with a wooden pestle, that it may pass through the holes. When it is entirely passed, you introduce another copper strainer, with holes still smaller than the former, to prevent the impurities of the gum from escaping. The liquor of the gum already dissolved is poured into this strainer, and again passed as before by the help of the pestle. This operation is made more easy, by now and then taking out the strainer and resting it on a cross shelf or plank, suspended on the peg over the copper used for wringing the black. The gum must be squeezed pretty hard with the pestle to force it through the holes of the strainer.

"The gum would dissolve with more facility if previously steeped for three or four days in the logwood decoction, especially if you are careful to pour it on very hot.

"When the above ingredients are put into the black ground, you must remember to keep the liquor hot enough to dissolve the gum and the salts, but it should never be suffered to boil; and when it is therefore sufficiently hot, the fire is taken away, and the fresh iron-filings sprinkled over it in a proper quantity to cover the liquor.

"The next morning the fire is again put under the copper, the drugs boiled, and the logwood a second time boiled. It is then taken out, and the following drugs added to this second decoction, viz.

These drugs are boiled, the liquor strained and poured on the black ground as we have already said, and the grounds preserved. You then put a little fire under the copper as at first, and the following drugs are immediately added, viz.

"When the liquor is hot enough, you take away the fire, strewing over the liquor with the iron-filings, and letting it stand for three or four days.

"Two pounds of verdigris are then pounded and dissolved with six quarts of vinegar in an earthen pot, adding to it about an ounce of cream of tartar. The whole should boil for a full hour, taking care to check the boiling with cold vinegar that it may not boil over. This preparation should be kept ready to be added to the black ground when you are going to dye."

"For the black dye the silk is boiled as usual; having washed and beetled according to custom, you give the gall liquor for heavy blacks twice, but for light blacks only once. These two blacks are alike both in beauty and shade, differing only in the weight of the silk: the light black has, however, rather more lustre.

"The nutgall liquor is made as follows: For every pound of silk you must have three-quarters of a pound of light nutgalls, adding the same quantity of Aleppo. These galls are pounded together, and boiled for two hours in a quantity of water sufficient for the whole of the silk to be galled. As the liquor wastes a great deal in the boiling, it is, after the first hour, filled again, and after two hours the fire is taken away; the liquor is then left to deposit, and the galls taken out with a pierced ladle; about an hour afterwards the silk is put into it, prepared as above.

During this operation the silk is drained and very lightly squeezed: it is then immersed in the gall liquor, on cords one above another, taking care to keep it near the surface of the liquor, but sufficiently covered. In this manner it should remain 12 or 15 hours; it is then taken out, washed at the river, and if intended for heavy black, is a second time galled in a fresh galling like the first; the grounds are generally used for the first galling; but for the second a liquor of fresh drugs.

"Some dyers gall the heavy blacks but once, by boiling the old grounds, taking them out immediately, and afterwards adding fresh galls; for every pound of silk a pound of light gall and half a pound of fine Aleppo. The fresh galls they boil for two hours or more, and when the grounds are taken out they put the

79
How to use
the native
gums in
this opera-
tion.

the silk in the fresh gall liquor, where they let it remain a day and a night.

" This method, they say, is the best; because, were the gall grounds to remain in the liquor, they would re-imbibé part of the substance which they had before given to the water.

" When the silk is galled, a little fire is put under the black ground; while it is heating, the silk is wrung out of the galling, and beetled at the river.

" When washed it is drained on the pegs, passing a thread round every hank, each hank as large as for common colours: it is then immediately put on the rods.

" While the black liquor is heating, it should be stirred with an iron rake or paddle, to prevent the grounds from sticking to the bottom of the copper. You then dissolve some French gum by the method above described, till it rises on the top in a kind of scum covering the surface of the liquor; afterwards you throw into it two or three handfuls of linseed. You then add half of the vinegar and verdigris preparation with about four or five pounds of copperas; this should be punctually repeated at every heating.

" Care should be taken whilst the fire is under the copper to rake; and, to try if it be hot enough, the rake is moved round at the bottom of the copper; if the gum sticks to the rake, and the liquor does not appear through the middle of the gummy scum, it shows that it is hot enough: the fire is then taken away, because, as we have before observed, it should not boil. The rake is then also taken out, and the liquor covered with iron-silings in the same manner as before; after this it is suffered to subside for about an hour, when the surface of the liquor is again stirred, in order to precipitate the silings to the bottom.

" Before we explain the manner of dipping silk in the black liquor, it is proper to observe that silk-dyers never dye black but by copperas, that is when they have a sufficient quantity of silk for three dips, if for heavy black; but if light black only two dips, which is done in the following manner:

" If heavy black, a third of the silk is put upon the rods, and three times returned in the black ground; it is afterwards wrung on the peg over the copper; this is done by giving it three twists: in this manner three hanks may be wrung at once, because it should be done gently, and only to drain; it is again put on the rods, and suspended between two perches to air.

" While the first silk is airing, the second third part is dipped in the same manner, and afterwards the third third part, always in the same manner. It must be remembered, that while the silk is on the rods it should be turned from time to time to give it air.

" When the last third part is wrung, the first part is put in, and then the two others successively for three times, always airing at each time. This is commonly called giving the three wrings, and these three wrings are called one fire or heating.

" The light blacks should also have three wrings to one fire.

" After each fire the black ground is again heated, adding copperas and gum as before. This operation is thrice done for the heavy blacks, that is three fires, each fire consisting of three wrings; but for light blacks only twice, each also consisting of three wrings.

" It must be observed, that at every reheating it is requisite to change the order of dipping, in such a manner that each may in its turn have the first of the liquor. If the black dye is strong and good, the heavy blacks may be done with two fires only; and for the light blacks one wringing less may do for each heating.

" When blacks are finished they are returned in a trough of cold water by dips one after another, called by the French dyers disbroder or rinsing; they are then twice or thrice beetled at the river. When washed you put them on the cords, only taking care not to press them too much.

" The silk when taken out of the black dye is extremely harsh, which is by no means wonderful, considering the number of acids and corrosives in the composition. It is therefore necessary to soften it in the following manner:

" Dissolve about five pounds of soap in two buckets of water; and while the soap is dissolving, throw in black silks a handful of aniseed or any other aromatic plant. It should boil till the soap is entirely dissolved. In the mean time a trough should be provided full of cold water, and large enough to dip all the silk at the same time. The soap-water should be strained through linen, the whole mixed well together, and the silk put in, where it should remain a full quarter of an hour. It is then taken out, wrung on the peg, and dried as usual. As the quantity of soap can do no harm, too much is better than too little. This softening is very necessary, in order to divest the silk of that rustling and stiffness so prejudicial in the manufacture of black goods.

" To dye black in the raw, the silk should be galled to dye in a cold liquor of fresh galls, which had been previously used for the boiled silk. The natural yellow of the silk is preferable for this dye, because the white takes a less beautiful cast.

" Having untied the silk and divided it into hanks of the common size, it is dipped with the hands into the gall liquor. When soaked and a little squeezed, it is strung on cords, eight or ten hanks together.

" They are afterwards put into the cold gall-liquor, one above another, letting even the cords sink in the liquor, where they may remain for six or seven days. They are then taken out and once beetled at the river. As to time, it should remain in the galling according to the strength of the liquor and the quantity of the silk put into it; but however strong it may be, and however small the quantity of silk, it should remain two or three days at least.

" When the silk is washed, it is again strung on the cords and left to drain, after which the cords are put one over the other into the rinsing or black wash, which is of itself sufficient to dye; it will, however, require more or less time according to the strength of the rinsing wash, generally about three or four days. Whilst the silk is thus immersed in the rinsing water, it should be raised with sticks three or four times a day; it is then drained over the liquor, and when drained put on the ground in a proper place, where it is spread and aired, but not dried. This is absolutely necessary to produce the black, else the silk might take a black-grey; this grey would, however, blacken in the air: nevertheless you are thereby enabled to

judge how much of the colour it has taken, and how much it may still want. Should the silk be suffered to dry, it must be again wetted before it is re-dipped, which would be an additional and unnecessary trouble.

"This operation of washing and drying must be successively continued till the silk is sufficiently black.

"The silk in this situation is carried to the river, and twice beated; after which it is drained on the cords, and then put on the perches to dry without wringing, which would soften it too much: for as this kind of silk is designed for gauzes and black lace, care should be taken to preserve its natural stiffness as much as possible.

"To produce black in the raw in the quickest manner, the silk when washed from its galling should be put on the rods and three times returned in the blacking ground; it is then taken out, and put to drain over the vessel containing the black liquor, and then cooled on the rods.

"When drained, it is again twice dipped in the black liquor, drained, and each time cooled as at first. When drained, it is again washed; and the procedure is then the same as for those which had been dyed in the rinsing. This is not, however, the usual method of dyeing black in the raw; because it consumes the black liquor too soon, considering with what avidity the raw silk takes any colour whatever; and besides that a good rinsing is sufficiently strong for dyeing this colour.

"The black dye is weakened and becomes exhausted in proportion to the silk it has dyed; it is therefore necessary to strengthen and replenish, from time to time, by an addition of proper drugs, which is called giving the brevet or composition.

"This composition is made by putting four or five buckets of water into a copper, and then boiling it with about four pounds of logwood chips. The logwood is then taken out, and four pounds of black buckthorn berries is added with two pounds of pomegranate rind, two pounds of sumach, two pounds of Cogue de Levant, two pounds of coliquinte, two pounds of linseed, and four pounds of cummin.

"These drugs are boiled together for about three quarters of an hour; the fire is then put under the black liquor, when a little more than half boiled, and whilst hot the following drugs are added, viz.

"These drugs, when all pounded, are thrown into the black ground, remembering to stir. When the composition is sufficiently boiled, it is strained in a trough and left to settle; the grounds having subsided, the clear part is added to the black ground. The same grounds are again boiled and preserved for some other time.

"The composition being added to the black liquor, and sufficiently hot, the fire is taken away. The liquor is then strewed over with the iron-silings, and left to settle for two days.

"When the black ground has had a certain number

of additions, and a quantity of sediment collected at the bottom, part of the grounds should be taken out in order to clear the liquor. Thus frequently replenishing, the foundation is always preserved; so that the liquor is never entirely new, but having been once set in a dye-house is set for ever. These liquors are never liable to putrefaction, owing to the great quantity of nutgalls and martial vitriol in the composition, two of the most powerful antiseptics known.

"The most material observation concerning the black dye is, that in general it greatly injures the goods in such a manner that stuffs of this colour, though not inferior in other respects, wear out much sooner than those of any other. This defect may be attributed to the vitriolic acid of the copperas, which is but imperfectly saturated with the iron. Iron combined with any, even vegetable, acid, is capable of producing black with vegetable altringents. It is therefore most probable that this inconvenience might possibly be removed, by substituting other combinations of this metal for the copperas, if it were worth while to make the attempt."

"All kinds of grey, excepting black grey, are produced upon silk without aluming. The silk being washed from the soap and drained on the peg, a liquor is made of fustic, logwood, archil, and copperas. Fustic gives the ground: archil the red; logwood darkens, and the copperas softens all these colours, turns them grey, and at the same time serves instead of alum in extracting them. As there is an infinite variety of greys without any positive names, and produced by the same methods, it would be endless to enter into a detail that would prolong this treatise to so little purpose. 8a

Suffice it to remark here, that in producing a reddish grey the archil should predominate; for those more grey, the logwood; and for those still more rusty and rather greenish, fustic.

In general, when obliged to complete the colour with logwood, it should be used rather sparingly, because it is apt in drying to darken too much, differing in this particular from all other colours.

To give an example of the manner of producing these colours we shall take the nut-grey.

The fustic decoction, archil, and a little logwood, is put into water moderately hot. The silk is then returned, and when the liquor is exhausted it is taken out; and to soften the colour the copperas solution is added. Some dyers for this purpose add the black wash instead of the copperas; the silk is again returned; and if the colour does not appear sufficiently even, some red spots still remaining, it may be concluded that it requires a little more copperas.

It must also be remembered, that as copperas is the general base of all greys, if deficient in quantity, the colour will be apt to change in drying, and to become rough and uneven.

To try if the colour be sufficiently softened, it should be examined; and if it wets easily, after having been wrung on the peg, it wants copperas; but if on the contrary it soaks with a little difficulty, the colour is enough softened.

On the other hand, too much copperas stiffens the silk considerably, making it harsh, and even depriving it of a great part of its lustre. To remedy this, the silk

filk when taken out of the liquor should be wrung on the peg, and then immediately washed at the river, which carries off the superfluous copperas.

The black greys, because alumed and welded, make a separate class. When the filk is alumed and cooled at the river, and the weld liquor prepared as for yellows, the filk is returned; and when the liquor is exhausted, a part of it is thrown away, and the logwood decoction substituted in its place. The filk is again returned in this liquor; and when the logwood is exhausted, some copperas may be added in a sufficient quantity to blacken the colour. The filk is then washed, wrung, and finished as usual.

For iron grey, it is necessary to boil the same as for blues. This colour is much more beautiful when laid on a very white ground. It is more used in the manufacturing of stockings than any other colour, therefore generally wrought in shades; that is, many different shades made at the same time.

When the filk is washed and prepared as usual, you make the liquor of river or well water, no matter which; but either must be cold.

If river water, the logwood decoction made with river water is added, sufficient to produce the dark shade required; the filk is then dipped, and when finished it is wrung and hung up. A part of the liquor is then thrown away and replenished with water for the following shades, and so on to the lightest, carefully dividing; that is, preserving an equal distance between the shades.

When all is finished with the logwood, the dark shades are put again on the rods, to be dipped in a new liquor with the addition of copperas; the remaining lighter shades are then dipped in the same liquor, but without the copperas addition: if, however, the second shade is not enough softened, a little copperas must be added. This defect is easily perceived in the dipping, as we have before observed.

When arrived at the lightest shades, care should be taken that the liquor be not overcharged with copperas, which is easily perceived by its having a reddish cast; in which case some of the liquor should be thrown away and replenished with water, too much copperas producing the same effect with regard to these shades as the preceding.

When the liquor is made with well water, the logwood decoction should also be made of well water. This being added to the liquor, the darkest shades are first dipped as in the preceding process. When the filk has sufficiently drawn, it is taken out, and the following shades are then dipped, but without replenishing, the colour being much better and clearer without the river water.

When all the shades are complete, you soften with copperas, in the same manner as above described; the filk is afterwards washed, and if necessary beated.

To discharge greys, that is when the shades are too dark and too full, you put some tartar pounded in a mortar and sifted into a bucket or small trough; you then pour over it some boiling water. The clearness of this liquor is afterwards put in a trough, and the filks returned in it; by which operation a part of the colour is immediately discharged.

If the filk does not instantly take an equal colour, a little more tartar must be added as above mentioned.

The filk thus discharged of its superfluous colour is once beated at the river, and afterwards dipped in hot water, without any other addition. This last operation restores in part what it had lost by the tartar; but to try the colour it should be wrung on the peg.

The tartar always destroying some part of this colour, it should be restored with a fresh liquor made for the purpose, and then softened with copperas as usual.

If the filk has been alumed, then the hot water may be omitted after the beating; the hot water is, however, always of use in removing the harshness occasioned by the tartar.

To discharge iron greys when too dark, they should be sulphured, afterwards beated at the river, and then again dipped in a fresh liquor similar to the first.

This method of discharging iron greys is preferable to either tartar or lemon juice, these ingredients giving them a ground that does not easily yield even to the boiling with soap, which consequently spoils the colour; whereas the sulphuring almost entirely whitens the filk by totally destroying the logwood.

For greys in the raw, the filk should be as white as for common colours, except the black grey, for which the natural yellow would be no disadvantage. Having soaked the raw filk, the process is then the same for producing these shades as on boiled filk.

Cotton or linen receive a black colour with still more difficulty than filk. "The various processes (says M. de Apligny) for dyeing black, agree in the sole intention of introducing within the pores of the stuff ferruginous particles dissolved in different menstrua, and of precipitating them on the stuff by means of astringent substances furnished with phlogiston capable of colouring iron black. The best method therefore of succeeding, is to choose a solvent capable of dividing the particles so minutely that the calx may not injure the stuff. Copperas or green vitriol are used in these processes; but the iron it contains is by no means in a state of perfect division, on account of the phlogiston obstinately retained by it, which facilitates its union with the acid without the iron being perfectly dissolved. It is for this reason, doubtless, that a solution of green vitriol in water deposits in lime a species of ochre; which, according to M. Geoffroy, seems to be an extraneous substance. For the same reason the spirit of nitre, saturated with iron, will dissolve still more, by abandoning the grosser particles of what is held in solution, and of which it retains only the phlogiston.

"This being the case, whenever copperas is used in dyeing of black, the stuff dyed are generally harsh to the feel and considerably damaged; because the gross particles of the iron being only divided, and not dissolved by the vitriolic acid of the copperas, overspill the pores of the stuff into which they had entered, and by their hardness extending the partition of these pores, force them asunder. M. Hellot very well observes, that cloth-dyed black without a blue or root ground requires a greater quantity of copperas, by which the stuff is rendered rotten; but I have also remarked, that when dissolving the rust of iron in vinegar, either for yellow or for the black of painted linens, it is apt to tear in the parts where these colours are applied, particularly if there has been no attention to take off the grosser earth by scumming the solution. To this

this earth therefore the rottenness of black stuff may be attributed; and not, as vulgarly imagined, to the salt of vitriol, nor to any other burning cause.

“And therefore, in order to render the colour more equal, and the stuffs less damaged, the best method for black is to use a solution of iron perfectly divided. Consequently, as experience daily teaches, those acids which attack the iron too rapidly are the least proper to produce a perfect solution of this metal. Weak acids are therefore preferable; which, notwithstanding their slow operation, penetrate entirely, dividing it into impalpable particles. Black compositions also succeed much better in proportion as the black liquor is older, and consequently the solution of the iron more complete. The manufacturers in India are so truly sensible of this consequence, that many of them preserve their black vats for more than 20 years. In the states of Genoa, Florence, and Naples, every manufacturing city has a place of reserve, called the Seraglio, where at the public expence eight or ten vats are continually supported. These vats have been set from 300 to 400 years, more or less; that is, prepared for the dipping of silk designed for black, and requiring only to be supplied with proper drugs in proportion as they are diminished by use. The ground remaining always the same, forms a kind of leaven, by which the fermentation of the necessary additional drugs is assisted.

“The process at Rouen for dyeing linen and cotton thread black, is first to give it a sky-blue ground, and then to wring and dry. It is afterwards galled, a quarter of a pound of galls for every pound of the substance (as for reds); having remained 24 hours in the gall liquor, it is again wrung and dried.

“About five quarts of the black liquor for every pound is then poured into a trough. The cotton is then dipped and worked with the hand, pound by pound, for about a quarter of an hour, then wrung and aired. This operation is twice repeated, adding each time a fresh quantity of the black liquor carefully scummed. It is again aired, wrung, washed at the river, well drained, and dried.

“When this cotton is to be dyed, about one pound of the rind of the alder-tree for every pound of thread is put into a copper and boiled in a sufficient quantity of water during one hour. About half the liquor that had been used for the galling is then added, with about half the weight of the rind of the alder or sumach. The whole is again boiled for two hours, after which it is strained through a sieve. When it is cold, the cotton is dipped in it on the rods, and worked pound by pound; from time to time airing, and returning it into the liquor; where having remained 24 hours, it is wrung and dried.

“For softening this cotton when too harsh, it is the custom to soak it in the remainder of the weld-liquor that had been used for other colours, adding a little of the logwood-liquor. It is then taken out, and instantly plunged into a trough of warm water, into which had been poured about an ounce of the oil of olives for every pound of the substance: it is then wrung and dried.

“M. l'Abbé Mazéas has given a process for the dyeing of linen and cotton thread black, by maddering after having prepared with the fickion of the A-

drianople red, galling and dipping in an astringent composed of lime-water and green copperas calcined. This process, though long and expensive, is in my mind no better than those I have just described. In order to obtain a permanent black, it is my opinion that we must still have recourse to the black resulting from a combination of the three primitive colours, until we discover feculae capable of yielding a direct black. I shall now describe a process in which I myself have succeeded perfectly.

“To dye linen and cotton thread black by a combination of colours, it is necessary to begin by cleaning the thread as usual by galling, in the same manner as mentioned in the article upon red, aluming afterwards, and then dipping in a weld-liquor. When taken out of this liquor, it must be dyed in a decoction of logwood, to which has been added a quarter of a pound of blue vitriol for every pound of the substance. It is then taken out, washed at the river, wrung, and washed several times, but not wrung hard. It is at last dyed in a madder liquor, about half a pound of this dye for every pound of the substance. It is needless to repeat here the manner of galling, aluming, and welding, &c. having described them above. By this process we may rest assured of obtaining a very beautiful and permanent black, that will not be liable to be discharged, provided that after having been dyed the thread be dipped in a boiling soap-liquor.

“Several different shades of grey are distinguished in the art of dyeing; viz. black-grey, iron-grey, slate-grey, thorn-grey, agate-grey, &c. It is easy to conceive, that grey in general, being a mixture of black and white, its different shades can be obtained only by introducing into the subject a small quantity of matter, by which the rays of light are absorbed in such a manner, that some of the pores not being occupied, reflect all the rays, and present to the eye a grey colour by means of the black particles contained in the intermediate pores. This operation in dyeing is therefore precisely the same as in painting, which produces grey by a mixture of lamp-black and of white lead.

“It would be too tedious, and even superfluous, to describe the different processes for the several greys just mentioned. The dyer will be better able to judge of these shades by his eye than by any particular rules. All that can be said is, that it is the common practice to give a blue ground to black-grey, iron-grey, and slate-grey; but to none of the others. These shades require aluming in proportion to the shade wanted, and are even frequently galled with liquors that had been previously used.

“The thread having been first galled, wrung, and dried, is dipped on the rods in a trough full of cold water, adding an arbitrary quantity of the black liquor and of the logwood decoction. The thread is then worked pound by pound, washed, wrung, and dried.

“It is possible to produce more permanent greys by the two following processes. First, by galling the thread, by dipping in a very weak black vat or liquor, and afterwards maddering. Secondly, by dipping the thread in a very hot solution of crystals of tartar, lightly wringing, and then drying. The thread is then dyed in a decoction of logwood. It appears black; but by dipping the thread, and working it attentively in a hot solution of soap, the superfluous dye being discharged,

ged, it remains a slate-grey, very pretty and very permanent."

Having described in such a particular manner the methods of dyeing the primitive colours, there can be very little difficulty in comprehending the management of those which proceed from a mixture of them. But though an infinite number of different shades may be formed from those already mentioned, we are not to imagine that a good colour will be produced by the mixture of any two at random. Thus, though you mix blue and scarlet together in any way you please in order to produce a purple, the colour will neither be good nor uniform, owing to the opposite action of the acid and alkaline ingredients by which these two primitive colours are struck. With crimson the case is altered: for, as we have already seen, that colour is produced in the greatest perfection where volatile alkali is concerned; and therefore the alkaline ingredients of the blue, which can only tend to heighten that property in the other colour, have no such pernicious tendency. From a mixture of blue and crimson, therefore, are produced columbine, purple, amaranth, penfy, violet, with innumerable other shades, varying according to the depth of the original colours employed. In all these compound colours, it is necessary to dye the stuff completely of one colour, and then proceed with it for the other exactly as if it had been quite white. In the present case, you must begin with blue; because, though the indigo cannot be hurt by the ingredients necessary for dyeing crimson, yet the cochineal would be very considerably injured by the lime used for dissolving the indigo. Colours of an inferior kind are produced from madder.

Blue and yellow produce a green, which is always essentially the same; though there are also innumerable shades of it which go by different names, as yellow-green, pale-green, bright-green, grass-green, sea-green, olive-green, &c. &c. These are all dyed by the general method already mentioned, viz. a yellow dye superadded to a blue ground; though they differ in some particulars in respect to the various shades above mentioned.

For yellow-greens, M. Hellot directs the stuff to be a fine light blue, boiled with the common quantities of alum and tartar, and then dipped in the yellow dye in order to receive a strong colour, that the yellow may predominate. For those shades called cabbage and parrot green, or any others more inclining to blue, it is requisite that the latter should be very deep and the yellow dye weak, or that a smaller quantity of salts should be used in the preparation. This last method, however, is not approved of by M. Hellot; and indeed it is natural to think, that a great quantity of colour with little of the preparation necessary to make it adhere and brighten it, must be much less durable, as well as less beautiful, than one where the colour and preparation are in due proportion to one another.

A very beautiful green will be produced by dipping a deep blue cloth in the decoction of the virga aurea Canadiensis, provided the stuff after being dyed blue has been boiled in a solution of three parts of alum and one of white tartar. This green is equally permanent with that dyed with weld. A very permanent green is also produced by the bark of the alr-tree, but less beautiful than the other. A duck's-wing

green is produced by using the root of the sharp-pointed dock grossly powdered and in sufficient quantity. For this the stuff must be dyed first of a dark blue; then well scoured, and afterwards boiled in a solution of four parts of alum and one of tartar; and, lastly, it must be boiled full two hours with the other colouring ingredient the dock-root. By this root also many various shades of colour may be obtained from the palest yellow to a tolerable olive; so that our author thinks it is a considerable acquisition in the art of dyeing.

Sea-green is usually dyed, according to M. Hellot, with verdigris; and the following, he says, is the Dutch method of doing it, and which produces a more permanent colour than usually is obtained by means of that ingredient. "Two cauldrons are to be placed at a little distance from each other; in one of which you put two pieces of cloth of 40 or 50 clls in length, with eight or ten pounds of white soap shaved, and which must be perfectly dissolved. When the mixture is ready to boil, the stuff should be immersed, and suffered to boil a full half hour. In the other cauldron you must prepare another liquor; and when that is quite hot, you put into it a clean linen bag, containing eight or ten pounds of blue vitriol, and ten or twelve of lime, each of them well pulverized and mixed together; it being necessary that the mixture should be as accurate as possible. This bag should be moved about in the water, hot, but not boiling, till the vitriol is dissolved. A winch is then to be fixed on in the usual manner; but which ought to be carefully wrapped round with a clean linen cloth very tight and well sewed. One end of the cloth is fixed on the winch, which is then turned swiftly round, that the cloth may pass swiftly from the soap-cauldron into that with the vitriol; and here it is turned more slowly, that it may have time to imbibe the particles of the copper, which by means of the lime were diffused in the liquor by separating and precipitating them from the blue vitriol in which they were contained. The cloth is left in this liquor, which should never boil till the cloth has taken the sea-green colour desired. It is then to be taken out, drained on the winch, and aired by the lifting. It should hang till it is perfectly cold before it be washed at the river. If it touches wood it will be spotted; for which reason, the winch, and every thing of wood over which it must pass, ought to be well covered with linen."

On examining this process by the principles of chemistry, it appears to be no other than impregnating the cloth with a solution of copper in fixed alkali. It is undoubtedly a mistake to say, that it is done by verdigris; for no verdigris can be formed from blue vitriol, lime, and soap. All that we can say of it is, that it is cloth impregnated with a combination of copper with fixed alkali; which being naturally extremely ready to unite with water, and having very little attraction for the cloth, the latter may be supposed to be painted rather than dyed with it. A much better method, therefore, seems to be that recommended by M. Hellot, of first dyeing the stuff a very light blue, and then giving the necessary yellow with virga aurea.

These receipts may serve as specimens of the methods of dyeing all kinds of mixed colours. There are, however, methods of producing both a blue and green from indigo itself, by dissolving it in acids; and

the colours so produced are called Saxon blues and greens. Being perishable colours, they are now seldom used; though Mr Wolfe some time ago published a receipt in the Philosophical Transactions for preparing them after an improved method. This method, for the blue, was to dissolve indigo in concentrated oil of vitriol by digesting them in the heat of boiling water instead of sand, which had formerly been used, and was apt to spoil the colour. After the solution of the indigo, the liquor may be weakened at pleasure; and any piece of cloth dipped in it will imbibe a dye deeper or lighter according to the quantity of colour it contains. This colour is very beautiful, but apt to prove unequal; and, as has been already said, extremely perishable. For the Saxon green it is necessary to have a yellow from indigo also, which is obtained by dissolving it in spirit of nitre. Mr Wolfe recommends an ounce and an half of powdered indigo to be mixed with two ounces of spirit of nitre diluted with four times its quantity of water. The mixture is then to stand for a week, and at the end of that space is to be digested in a sand heat for an hour or more; after which four ounces more of water are to be added. The solution, when filtered, will be of a fine yellow colour. Strong spirit of nitre, when mixed undiluted with indigo, is apt to set fire to it; for which reason the water is added. Even in its diluted state, it will froth and run over if the digestion be performed within 24 hours after the mixture; and on this account it is allowed to remain a week in the cold. One part of the solution of indigo in the acid of nitre, mixed with four or five parts of water, will dye silk or cloth of the palest yellow colour, or of any shade to the deepest, by letting them boil a longer or shorter time, adding water as the liquid evaporates. The addition of alum makes the colour more lasting. None of the colour separates in the operation but what is imbibed by the cloth, and therefore this liquid goes very far in dyeing. That part of the indigo which remains undissolved in the vitriolic acid, when collected by filtration and dissolved in spirit of nitre, will dye silk and wool of all shades of brown inclining to yellow.

On the process for dyeing Saxon blue M. de Apligny observes, that there is no real solution of the indigo in the acid of vitriol, but that it is only divided into very fine particles and suspended in the liquor; neither can any alteration be made in it by an alteration in the process. Nor does this make any exception to the general rule in chemistry, that acids dissolve and redden the blue colouring matter of vegetables; it not being their nature to act upon feculae such as indigo, but upon vegetable juices, the colour of which depends on the salts and essential oil of the plant. For the truth of his assertion he appeals to the appearance of the liquor prepared for dyeing Saxon blue.

From the vast profusion of colours which nature exhibits in the flowers which grow every where around us, it is natural to think that the materials for dyeing might be had in the greatest plenty without any necessity of having recourse to foreign countries. But this is far from being the case: for scarce one of our blue or red flowers can be made to communicate any durable colour to cloth; while, on the other hand, almost all the yellow ones may be made to do so. Numberless experiments have been made to determine the plants

which might be really useful to dyers; and most that have yet been found fit for their purpose in Britain are comprehended in the following list.

As it is often necessary to give another colour to How to discharge colours which have been already dyed, it is plain, that it is as necessary for a dyer to know how to discharge colours as how to make the cloth imbibe them.—Concerning this, it is only necessary to observe, that alkaline salts are in general the best, and, where the colours are well dyed, the only means of discharging them. If a piece of cloth is dyed with logwood, and the colour struck upon it with alum, that colour will be nearly discharged by oil of vitriol, or any other strong acid; but if solution of tin has been employed in striking the colour, acids have then no effect, and alkalies only can be employed. Neither will they discharge the colour totally, but the stuff must be bleached for some time to get out the remainder. If alkaline salts cannot be employed with safety to the stuff, it is then impossible to dye it any other colour than black; unless it be dyed

a compound colour, of which the original one is a component part.

Concerning the weight that colours give to silk (in which it is most taken notice of, being sold by weight, and a commodity of great price), it is observed, that one pound of raw silk loseth four ounces by washing out the gums and the natural fordes; that the same scoured silk may be raised to above thirty ounces from the remaining twelve, if it be dyed black with some materials. Of all the materials used in dyeing, especially

of black, nothing increases weight so much as galls, by which black silks are restored to as much weight as they lost by washing out their gum; nor is it counted extraordinary, that blacks should gain about four or six ounces in the dyeing upon each pound. Next to the galls, old fustic increases the weight about 14 in 12; madder, one ounce; weld, half an ounce; the blue vats in deep blues of the fifth still give no considerable weight; neither do logwood, cochineal, nor even copperas, where galls are not used.

Dyeing
||
Dyspepsy.
DYEING of Hats. See HATS.
DYEING of Leather. See LEATHER.
DYEING, or Staining, of paper, wood, bone, marble, &c. See BONE, MARBLE, PAPER, WOOD, &c.
DYNASTY, among ancient historians, signifies a race or succession of kings of the same line or family. Such were the dynasties of Egypt. The word is formed from the Greek δυναστεία of δυνατός, to be powerful, or king.

The Egyptians reckon 30 dynasties within the space of 36,525 years; but the generality of chronologists look upon them as fabulous. And it is very certain, that these dynasties are not continually successive, but collateral.

DYRRACHIUM (anc. geog.), a town on the coast of Illyricum, before called Epidamnus, or Epidamnus, an inauspicious name, changed by the Romans to Durachium; a name taken from the peninsula on which it stood. Originally built by the Coreyreans. A Roman colony (Pliny). A town famous in story: its port answered to that of Brundusium, and the passage between both was very ready and expeditious. It was also a very famous mart for the people living on the Adriatic; and the free admission of strangers contributed much to its increase: A contrast to the conduct of the Apollonians; who, in imitation of the Spartans, discouraged strangers from settling among them.

DYSÆ, in mythology, inferior goddesses among the Saxons, being the messengers of the great Woden, whose province it was to convey the souls of such as died in battle to his abode, called Valhall, i. e. the hall of slaughter; where they were to drink with him and their other gods cerevisia, or a kind of malt liquor, in the skulls of their enemies. The Dysæ conveyed those who died a natural death to Hela, the goddess of hell, where they were tormented with hunger, thirst, and every kind of evil.

DYSCRASY, among physicians, denotes an ill habit or state of the humours, as in the scurvy, jaundice, &c.

DYSENTERY, in medicine, a diarrhoea or flux, wherein the stools are mixed with blood, and the bowels miserably tormented with gripes. See MEDICINE-Index.

DYSENTERIC FEVER. Ibid.

DYSERT, a parliament town of Scotland, in the county of Fife, situated on the northern shore of the frith of Forth, about 11 miles north of Edinburgh.

DYSOREXY, among physicians, denotes a want of appetite, proceeding from a weakly stomach.

DYSPEPSY, a difficulty of digestion.

VOL. VI. Part I.

DYSPNOEA, a difficulty of breathing, usually called asthma.

DYSURY, in medicine, a difficulty of making urine, attended with a sensation of heat and pain. See MEDICINE-Index.

DYTISCUS, WATER-BEETLE, in zoology, a genus of insects of the order of the coleoptera; the antennæ of which are slender and fetaceous, and the hind feet are hairy, and formed for swimming. There are 23 species, distinguished by their antennæ, the colour of the elytra, &c.

The larvæ of the dytiscus are often met with in water. They are oblong, and have six scaly feet. Their body consists of eleven segments. The head is large, with four filiform antennæ and a strong pair of jaws. The last segments of their body have rows of hairs on the sides; and the abdomen is terminated by two spines charged with the like hairs, forming a kind of plumes. These larvæ are frequently of a greenish variegated brown: they are lively, active, and extremely voracious: they devour and feed upon other water-insects, and often tear and destroy each other. The perfect insect is little inferior to its larvæ in voraciousness, but it can only exercise its cruelty on the larvæ; the perfect insects, like himself, being sheltered by the kind of scaly cuirass with which they are armed. This creature must be touched cautiously; for besides its power of giving a severe gripe with its jaws, it has moreover, under the thorax, another weapon, a long sharp spine, which it will drive into one's fingers by the effort it makes to move backwards. The eggs of the dytiscus are rather large, and are by them inclosed in a kind of silky dusky cod, of a strong and thick texture, in form round, and terminated by a long appendix or slender tail, of the same substance. These cods are often found in the water, and from them are brought forth the eggs and larvæ of the dytiscus. The strength of these cods probably serves the insect to defend their eggs from the voraciousness of several other aquatic insects, and even from that of their fellow-dytiscus, who would not spare them.

Many species of the perfect insect are common in stagnated waters, which they quit in the evening to fly about. They swim with incredible agility, making use of their hinder-legs after the fashion of oars. The elytra of the females are in general furrowed, and those of the male plain: when they first arrive at their perfect state, their elytra are almost transparent, and in many species of a beautiful dun colour, mingled with shades of greenish brown. The best method of

F f

catching