Of Simple Colours.

242. With the aluminous mordant, as it is usually applied by calico printers for madder reds, cotton dyed with cochineal receives a beautiful crimson colour, which will bear several washings, and resist the weather for some time. It is not, however, to be considered as a fixed colour. Dr Bancroft is of opinion, that the addition of a small portion of cochineal in dyeing madder reds upon the finer cottons, would be highly advantageous to the calico printers. By this addition the madder reds are rendered more beautiful, and the fawn colour, or brownish yellow hue, which injures these reds, would be thus overcome.

Sect. II. Of Yellow.

243. In dyeing yellow, it is necessary to employ mordants, because the affinity of yellow colouring matters for either animal or vegetable stuffs is not sufficiently strong to produce durable colours. Yellow colours, therefore, belong to that class which Dr Bancroft has denominated adjective colours. As in the former section, we shall first give a short description of the nature and properties of the substances employed in dyeing yellow, and then point out the most approved modes of communicating their colours to woollen, silk, cotton, and linen stuffs.

The substances capable of giving a yellow colour to different stuffs are very numerous; they do not all produce similar quantities of colouring matter; their dye is not equally free; the colours they impart incline more or less to orange or green; they possess various degrees of brightness and permanency, and differ considerably in price; circumstances by which the choice of the dyer ought always to be regulated. But those commonly employed in dyeing yellow, are weld, fustic, anotta, and quercitron bark.

I. Of the Substances employed in dyeing Yellow.

244. Weld (refedla luteola, Lin.) is a plant which grows wild in Britain, and in different European countries. Its leaves are long, narrow, and of a bright green, but the whole plant is made use of in the dyeing of yellow. There are two kinds of weld, cultivated and wild, the former of which is deemed more valuable than the latter, as it yields a much greater proportion of colouring matter. When this plant is fully ripe, it is pulled, dried, and bound up in bundles for the use of the dyer. The wild species grows higher and has a stronger stalk than that which is cultivated, by which the one may be readily distinguished from the other.

Properties. 245. A strong decoction of weld is of a brownish yellow colour, and if very much diluted with water, the colour inclines to a green. An alkali gives to this decoction a deeper colour, and the precipitate it occasions is not soluble in alkalies. Most of the acids give it a paler tinge, occasioning a little precipitate which is soluble in alkalies. Alumina has so strong an affinity for the colouring matter of weld, that it can even abstract it from sulphuric acid, and the oxide of tin produces a similar effect. The greater part of metallic salts throw down similar precipitates, which vary in their shades of colour according to the metal employed. A solution of common salt renders the liquor turbid, and a solution of tin yields a copious yellow precipitate, while the liquor long continues turbid, and slightly coloured.

246. Fustic (morus tinctoria, Lin.) is procured from Fustic, a tree of considerable magnitude, which grows in the West Indies. The wood is yellow, as its name imports, with orange veins. Ever since the discovery of America it has been used in dyeing, as appears from a paper in the Transactions of the Royal Society, of which Sir William Petty was the author. Its price is moderate, the colour it imparts is permanent, and it readily combines with indigo, which properties give it a claim to attention as a valuable ingredient in dyeing. Before it can be employed as a dye-stuff, it must be cut into chips and put in a bag, that it may not fix in, and tear the stuff, to which it is to impart its colouring matter.

247. When a decoction of yellow wood or fustic is Properties. made very strong, the colour is of a reddish yellow, and when diluted it is of an orange yellow, which it readily yields to water. It becomes turbid by means of acids, its colour is of a pale yellow, and the greenish precipitate may be re-dissolved by alkalies. The sulphates of zinc, iron, and copper, as well as alum, throw down precipitates composed of the colouring matter and the different bases of the salts employed.

In examining the causes of the fixity of yellow colours, obtained from vegetables, Chaptal discovered that the durability of the pale yellow depended on the tanning principle, which is found united with the yellow colouring matter. He obtained by analyzing fustic, 1. A resinous or gummy matter, which can communicate a beautiful yellow colour. 2. An extractive matter, which is also yellow, and affords a beautiful colour. 3. A tanning principle of a pale yellow colour, which becomes black by boiling, or exposure to the air. This latter diminishes the brilliancy of the two former; but it may be separated by a simple process. Chaptal boiled with the wood some animal substance containing gelatinous matter, such as bits of skin, strong glue, &c. The tanning principle was thus precipitated with the gelatinous matter, and the bath held in solution only the colouring matters which yield a bright, full yellow; and by means of this process he procured colours from several vegetables, equally bright with those which are communicated by yellow wood and quercitron bark.

248. Anotta is a species of paste of a red colour, obtained from the berries of the bixa orellana Lin. Ancati, which is a native of America. The anotta of commerce is imported from America to Europe in cakes of two or three lib. weight, where it is prepared from the seeds of the tree mentioned above; but the Americans are said to be in possession of a species of anotta superior to that which they export, both for the brilliancy and

Of Simple and permanency of the colour it imparts. They bruise the seeds with their hands moistened with oil, separating with a knife the paste as it is formed, and drying it in the sun; but the seeds are pounded with water when defined for sale, and allowed to undergo the process of fermentation.

Properties. Anota yields its colouring matter more readily to alcohol than to water, on which account it is used in yellow varnishes to which an orange tinge is intended to be given. Acids form a precipitate with a decoction of anota of an orange colour, which is soluble in alkalies; but solutions of common salt produce no sensible change. It yields an orange precipitate with a solution of alum, and the sulphates of copper and iron produce effects of nearly a similar nature. With a solution of tin the precipitate is of a lemon colour, and slowly depoited.

Quercitron bark.

Phil. of Perm. Gel. 319.

The bark of it yields a considerable quantity of colouring matter, which was first discovered by Dr Bancroft in the year 1784, in whom the use and application of it in dyeing were exclusively vested for a certain term of years by virtue of an act of parliament. To prepare it for use, the epidermis is taken off and pounded in a mill, the result of which process is a number of filaments and a fine light powder; but as these do not contain equal quantities of colouring matter, it will be proper to employ them in their natural proportions.

Properties. Quercitron bark readily imparts its colouring matter to water at 100° of Fahrenheit, which is of a yellowish brown, capable of being darkened by alkalies, and brightened by acids. With muriate of tin the precipitate is copious, and of a yellow colour; with sulphate of tin it is a dark olive; and with sulphate of copper it is yellow, but inclining to an olive. Nitro-muriate of tin yields a yellow extremely beautiful, probably owing to the oxide of tin combining with the colouring matter in a greater proportion than some other salts.

Other substances. Besides the substances already mentioned as employed in the dyeing of yellow, we may add saw-wort to the number (Jerratula tinctoria, Linn.) a plant which yields a colouring matter nearly similar to that of weld, and may of consequence be used as a proper substitute. Dyers broom (Genista tinctoria) produces a yellow of very indifferent nature, and is therefore only employed in dyeing stuffs of the coarsest kind. Turmeric (Curcuma longa) is a native production both of the East and West Indies, and yields a more copious quantity of colouring matter than any other yellow dye-stuff; but it will probably never be of any essential service in dyeing yellow, as no mordant has yet been discovered, capable of giving permanency to its colour.

Chamomile (Anthemis tinctoria) yields a faint yellow colour, the hue of which is not unpleasing, but is far from being durable, and even mordants are not capable of fixing it. Sulphate of lime, tartar and alum, bid fairest for success.

Fenugreek (Trigonella fenugraenum) yields seeds which, when ground, communicate to stuffs a pale yellow of tolerable durability; and the best mordants are found to be alum and muriate of soda, or common salt. American hickory (Juglans alba) is a tree, the bark of which yields a colouring matter in every respect resembling that of the quercus nigra, but in quantity greatly inferior. French berries (Rhamnus infectarius) produce a tolerable yellow colour, but it is by no means permanent. When used in the process of dyeing, they are to be employed in the same manner as weld. According to Scheffer, a fine yellow colour may be imparted to silk, thread and wool, by means of the leaves of the willow; but Bergman informs us that only the leaves of the sweet willow (Salix pentandra) are proper for producing a permanent colour, as a few weeks exposure to the sun extracts that which is produced by the colouring matter from the leaves of the common willow.

In Switzerland and in England, the seeds of purple trefoil are sometimes employed in the art of dyeing, on which Vogler made a number of experiments, in order to ascertain what colours they would produce; and he found that a fine deep yellow was afforded by a bath made of a solution of these seeds with potash; that sulphuric acid yielded a light yellow, and sulphate of copper or blue vitriol, a yellow inclining to green. M. Dize informs us, that the seeds of trefoil impart to wool a beautiful orange, and to silk a greenish yellow; and that while alumining is necessary in the process of dyeing with the seeds of trefoil, a solution of tin cannot be employed.

II. Of the Processes for Dyeing Wool Yellow.

In dyeing woollen stuffs with weld, the mordants employed are alum and tartar, and by their means a pure, permanent yellow is obtained. The boiling is to be conducted in the usual way; and according to Hellot, four ounces of alum to one ounce of tartar are to be employed. Other dyers, however, employ half as much tartar as alum. The colour is rendered paler, but more lively, by means of the tartar.

The bath is prepared by boiling the plant inclosed in a thin linen bag, and keeping it from rising of the bath by means of a wooden crofs. Some boil it till it sinks to the bottom of the vessel, while others, after it is boiled, take it out, and throw it away. From three to four lbs. of weld, and sometimes less, are allowed for every lb. of stuff; but the quantity must be regulated by the intensity of the shade desired. Some dyers add a small quantity of quicklime and ashes, which are found to promote the extraction of the colouring matter. These substances at the same time heighten the colour, but render it less susceptible of resisting the action of acids.

With other additions, and different management, different shades may be obtained. Thus, lighter shades are produced by dyeing after deeper ones, adding water at each dipping, and keeping the bath at the boiling temperature. These shades, however, are less lively than when fresh baths are employed, with a suitable proportion of weld. The addition of common salt or sulphate of lime to the weld bath communicates a richer and deeper colour. With alum it is paler and more lively, with tartar still paler, and with sulphate of iron the shade inclines to brown. According to Scheffer, by boiling the stuff two hours, with one-fourth of its weight of a solution of tin, and the same proportion of tartar, and then washing and boiling it with an equal weight of weld, a fine yellow is produced; but if the stuff... stuff be in the state of cloth, its internal texture is not penetrated. Poerner recommends a similar preparation as for dyeing fustic, and by these means the colour is brighter, more permanent, and lighter.

257. Dr Bancroft recommends the quercitron bark as one of the cheapest and best substances for dyeing wool yellow. The following is the simple process which he has proposed for its application. The bark is to be boiled up with about its weight, or one-third more, of alum, in a suitable proportion of water, for about 10 minutes. The stuff previously scoured is then to be immersed in the bath, taking care to give the higher colours first, and afterwards the paler straw colours. By this cheap and expeditious process, colours which are not wanted to be of a full or bright yellow, may be obtained. The colour may be considerably heightened by passing the unrefined stuff a few times through hot water, to which a little clean powdered chalk, in the proportion of about 1/4 lb. for each 100 lbs. of stuff has been previously added. The bark, when used in dyeing, being first reduced to powder, should be tied up in a thin linen bag, and suspended in the liquor, so that it may be occasionally moved through it, to diffuse the colouring matter more equally.

258. But although the above method possesses the advantages of cheapness and expedition, and is fully sufficient for communicating pale yellows; to obtain fuller and more permanent colours, the common mode of preparation, by previously applying the alumino-mordant, ought to be preferred. The stuff, therefore, should be boiled for about one hour or one hour and a quarter, with one-sixth, or one-eighth of its weight of alum, dissolved in a proper proportion of water. The stuff is then to be immersed without being rinsed, into the dyeing bath, with clean hot water, and about the same quantity of powdered bark tied up in a bag, as that of the alum employed in the preparation. The stuff is then to be turned as usual through the boiling liquor, until the colour appears to have acquired sufficient intensity. One pound of clean powdered chalk for every 100 lbs. of stuff is then to be mixed with the dyeing bath, and the operation continued for eight or ten minutes longer. This addition of the chalk raises and brightens the colour.

259. Orange Yellow.—To communicate a beautiful orange yellow to woollen stuffs, 10 lbs. of quercitron bark, tied up in a bag, for every 100 lbs. of stuff are to be put into the bath with hot water. At the end of six or eight minutes, an equal weight of muriato-fulphate of tin is to be added, and the mixture well stirred for two or three minutes. The cloth, previously scoured, and completely wetted, is then immersed in the dyeing liquor, and briskly turned for a few minutes. By this process the colouring matter fixes on the cloth so quickly and equally, that after the liquor begins to boil, the highest yellow may be produced in less than 15 minutes.

260. High shades of yellow, somewhat similar to those obtained from quercitron bark by the above process, are frequently given with young fustic (Chus cotinus, Lin.) and dyers spirit, or nitro-muriate of tin; but this colour is much less beautiful and permanent, while it is more expensive than what is obtained from the bark.

261. Bright golden Yellow.—This colour is produced by employing 10 pounds of bark for every 100 lbs. of cloth, the bark being first boiled a few minutes, and then adding seven or eight lbs. of muriato-fulphate of tin, with about five pounds of alum. The cloth is to be dyed in the same manner as in the process for the orange yellow.

262. Bright yellows of less body are produced by employing a smaller proportion of bark, as well as by diminishing the quantity of muriato-fulphate of tin and alum. And indeed every variety of shade of pure bright yellow may be given by varying the proportions of the ingredients.

263. To produce the lively delicate green shade, which, for certain purposes, is greatly admired, the addition of tartar, with the other ingredients, only is necessary, and the tartar must be added in different proportions, according to the shade which is wanted. For a full bright yellow, delicately inclining to the greenish tinge, it will be proper to employ eight pounds of bark, six of muriato-fulphate of tin, with six of alum, and four of tartar. An additional proportion of alum and tartar renders the yellow more delicate, and inclines it more to the green shade; but when this lively green shade is wanted in the greatest perfection, the ingredients must be used in equal proportions. The delicate green lemon yellows are seldom required to have much fulness or body. Ten pounds of bark, therefore, with an equal quantity of the other ingredients, are sufficient to dye three or four hundred pounds of stuffs.

264. To produce the exquisitely delicate and beautiful pale green shades, the surest method, Dr Bancroft observes, is to boil the bark with a small proportion of green yellow water, in a separate tin vessel for six or eight minutes, and then to add the muriato-fulphate of tin, alum, and tartar, and to boil them together for about fifteen minutes. A small quantity of this yellow liquor is then to be put into a dyeing vessel, which has been previously supplied with water sufficiently heated. The mixture being properly stirred, the dyeing process is to be conducted in the usual way, and the yellow liquor, as it is wanted, gradually added from the first vessel. In this way, the most delicate shades of lively green lemon yellows are dyed with ease and certainty. Weld is the only dye-stuff from which similar shades of colour can be obtained; but it is four times more expensive. The yellows dyed from quercitron bark, Dr Bancroft adds, with muriato-fulphate of tin and alum as mordants, do not exceed the expense of one penny for each pound of stuff; besides a considerable saving of time, labour, and fuel.

265. A greenish shade may also be produced without tartar, by substituting verdigris dissolved in vinegar, along with the bark; but it is neither so permanent, nor so bright and delicate, as that produced by means of tartar. Sulphate of indigo also, in very small proportion, communicates a similar shade, when it is employed with the bark, muriato-fulphate of tin, and alum; but it is apt to take unequally on the stuff, and besides, in the language of the dyers, the colour has a tendency to call or fly in the finishing.

266. Small proportions of cochineal employed along with the bark and other ingredients, raise the colour to a madder a beautiful orange, and even to an aurora. Madder employed may be also employed with the same view, for it heightens the yellow obtained from quercitron bark, although... Chap. I.

Of Simple Colours.

Although the colour thus obtained is inferior in beauty to that from cochineal. The madder may also be employed with weld for the same purpose.

267. The colours obtained from quercitron bark, by the processes which we have now described, are very durable. They resist the action of the air, of soap, citron bark and acids. It is by the effects of alum, but especially of tartar, that these colours become fixed as to remain permanent by exposure to the air. It is observed of the highest yellows, even when they approach to the orange, and which are best dyed, either with muriate, or muriato-fulphate of tin and bark, that although they resist the action of soap and acids, they are apt to lose their lustre and become brown by the effect of the sun and air; but this also happens to yellows dyed with nitro-muriate of tin, both with the bark and with weld, but in a still greater degree with other yellow vegetable colouring matters. In some of these this defect is less easily obviated by alum and tartar, than it is in the yellow obtained from weld and quercitron bark.

III. Of the Processes for Dyeing Silk Yellow.

With weld.

268. To dye silk a plain yellow colour, the only ingredient which was formerly employed is weld. The following is the process. The silk being previously scoured in the proportion of 20 lbs. of soap to the 100 of stuff, and then alumed and washed after the aluming, or as it is called, refreshed, the bath is prepared with two pounds of weld for every pound of silk; and, having boiled for 15 minutes, it is to be passed into a vat through a sieve or cloth. When the temperature is such as the hand can bear, the silk is introduced, and turned, until it has acquired a uniform colour. While this operation is going on, the weld is to be boiled a second time in fresh water; one half of the first bath is taken out, and its place supplied with a fresh decoction. The temperature of the fresh bath may be a little higher than the former, but it is necessary to guard against too great a degree of heat, that the colouring matter already fixed may not be dissolved. The stuff is to be turned as before, and afterwards taken out of the bath. A quantity of soda is to be dissolved in a part of the second decoction, and a larger or smaller proportion of this solution is to be added to the bath, according to the intensity of the shade required. When the silk has been turned a few times, it is again rung out, that it may be examined whether the colour be sufficiently full, and have the proper golden shade. To render the colour deeper, and to give it the gold cast, an addition of the alkaline solution is to be made to the bath, and to be repeated till the shade has acquired sufficient intensity. The alkaline solution may also be added along with the second decoction of the weld, observing the precaution, that the temperature of the bath be never too great.

269. To produce other shades of yellow, having more of a gold or jonquille colour, a quantity of anotta, proportioned to the shade required, is to be added to the bath, along with the alkali. Lighter shades of yellow, such as pale lemon, or Canary-bird colour, are obtained, by previously whitening the silk, and regulating the proportion of ingredients in the bath by the shade required. To communicate a yellow having a tinge of green, a little indigo is added to the bath, if the silk has not been previously azured. To prevent the intensity of the shade from being too great, the silk may be more slightly alumed than usual.

270. But, according to Dr Bancroft, the different shades of yellow obtained from weld, may be given to silk with equal facility and beauty, and at a cheaper rate, by employing quercitron bark as a substitute. A quantity of bark powdered and inclosed in a bag, in proportion to the shade of colour wanted, as from one to two pounds for every twelve pounds of silk, is put into the dyeing vat while the water is cold. Heat is then applied; and when it has become rather more than blood warm, or of the temperature of 100°, the silk having previously undergone the aluming process, is to be immersed and dyed in the usual way. If a deep shade is wanted, a small quantity of chalk or pearl-ashes may be added towards the end of the operation. To produce a more lively yellow, a small proportion of muriato-fulphate of tin may be employed; but it should be cautiously used, as it is apt to diminish the lustre of the silk. To produce such a shade, the proportions of the ingredients may be four pounds of bark, three of alum, and two of muriato-fulphate of tin. These are to be boiled with a proper quantity of water for ten or fifteen minutes; and the temperature of the liquid being so much reduced as the hand can bear it, the silk is immersed and dyed as usual, till it has acquired the proper colour. Care should be taken to keep the liquor constantly agitated, that the colouring matter may be equally diffused.

271. To dye silk of an aurora or orange colour, after being properly scoured, it may be immersed in an alkaline solution of anotta, the strength of which is to be regulated by the shade required; and the temperature of the bath should be between tepid and boiling water. When the desired shade has been obtained, the silks are to be washed and twice beetleed, to free them from the superfluous colouring matter, which would injure the beauty of the colour. When raw silk is to be dyed, that which is naturally white should be selected, and the bath should be nearly cold; for otherwise the alkali, by dissolving the gum of the silk, destroys its elasticity. Silk is dyed of an orange shade with anotta, but the stuff must be reddened with vinegar, alum, or lemon juice. The acid, by saturating the alkali employed to dissolve the anotta, destroys the yellow shade produced by the alkali, and restores its natural colour, which inclines to a red. But although beautiful colours are obtained by this process, they do not possess any great degree of permanency.

272. Several kinds of mushrooms afford lively and durable yellow dyes. A bright shining dye of this description has been extracted from the boletus luridus, which commonly grows on walnut and apple trees. The colouring matter is contained both in the tubular part, and also in the parenchyma of the body of the mushroom. To extract the colouring matter, it is pounded in a mortar, and the liquor which is thus obtained, is boiled for a quarter of an hour in water. An ounce of liquor is sufficient to communicate colouring matter to fix pounds of water. After the liquor has been strained, the stuff to be dyed is immersed in it, and boiled for fifteen minutes. When silk is subjected to this process, after being dyed, it is made to pass through a bath of soft soap, by which it acquires a shining appearance.

Of Simple Colours.

ing golden yellow colour, which has a near resemblance to the yellow of the silk employed to imitate embroidery in gold. This has been hitherto brought from China, and bears a very high price, the method of dyeing it being unknown in Europe. All kinds of stuff receive this colour, but it is less bright on linen and cotton, and seems to have the strongest affinity for silk. The use of mordants, it is supposed, would modify and improve it greatly.

IV. Of the Processes for Dyeing Cotton and Linen Yellow.

273. The process which has been usually followed in dyeing cotton and linen yellow, is by scouring it in a bath prepared in a ley with the ashes of green wood. It is afterwards washed, dried, and alumed, with one-fourth of its weight of alum. After 24 hours, it is taken out of the aluming, and dried, but without being washed. The cotton is then dyed in a weld bath, in the proportion of one pound and a quarter of weld for each pound of cotton, and turned in the bath till it has acquired the proper colour. After being taken out of the bath, it is soaked for an hour and a half in a solution of blue vitriol (fulphate of copper), in the proportion of one-fourth of the weight of the cotton, and then immersed, without washing, for nearly an hour, in a boiling solution of white soap, after which it is well washed and dried.

274. A deeper yellow is communicated to cotton, by omitting the process of aluming, and employing two pounds and a half of weld for each pound of cotton. To this is added a dram of verdigrise, mixed with part of the bath. The cotton is then to be dipped and worked till the colour become uniform. It is then taken out of the bath, that a little solution of soda may be added, after which it is returned, and kept for fifteen minutes. It is then wrung out and dried.

275. Other shades of yellow may be obtained, by varying the proportion of ingredients. Thus, a lemon colour is dyed by using only one pound of weld for every pound of cotton, and by diminishing the proportion of verdigrise, or using alum as a substitute.

276. But a better method, as it affords more permanent and more beautiful colours, and at a smaller expense, is recommended by Dr Bancroft. This is by the use of quercitron bark, and the calico printers' aluminous mordant, or the sugar of lead. The following is the process which he proposes to employ, for producing bright and durable yellow colours. One pound of sugar of lead, and three pounds of alum, are to be dissolved in a sufficient quantity of warm water. The cotton or linen, after being properly rinsed, is to be soaked in this mixture, heated to the temperature of 100°, for two hours. It is then taken out, moderately pressed over a vessel, to prevent the waste of the aluminous liquor. It is then dried in a stove heat, and after being again soaked in the aluminous solution, it is wrung out and dried a second time. Without being rinsed, it is to be barely wetted with lime water, and afterwards dried, and if a full, bright, and durable yellow is wanted, it may be necessary to soak the stuff in the diluted aluminous mordant, and after drying, to wet it a second time with lime water. After it has been soaked for the last time, it should be well rinsed in clean water, to separate the loose particles of the mordant, which might injure the application of the colouring matter. By the use of the lime water, a greater proportion of alumina combines with the stuff, besides the addition of a certain portion of lime.

277. In the preparation of the dyeing bath, from 12 lbs. of powdered quercitron bark are inclosed in a bath bag, for every 100 lbs. of the stuff, varying the proportion according to the intensity of the shade desired. The bark is put into the water while it is cold; and immediately after the stuff is immersed and agitated or turned for an hour, or an hour and a half, during which the water should be gradually heated, and the temperature raised to about 120°. At the end of this time the heat is increased, and the dyeing liquor brought to a boiling temperature; but at this temperature the stuff must remain in it only for a few minutes, because otherwise the yellow assumes a brownish shade. The stuff having thus acquired a sufficient colour, is taken out, rinsed and dried.

278. Dr Bancroft observes, that when the alumino-mordant is employed, without the addition of water, or a diluted tere, one soaking only, and an immersion in lime water, may be sufficient; but he thinks that greater advantage is derived from the application of a more diluted mordant at two different times, or even by the immersion of the stuff a greater number of times, alternately in the diluted aluminous mordant, and lime water, and drying it after each immersion. By this treatment he found, that the colour always acquired more body and durability.

279. Chaptal has proposed a process for communicating to cotton a nankeen yellow, which at the same time that it affords a durable colour, has the advantage of being cheap and simple. When cotton is immersed in a solution of any salt of iron, it has so strong an affinity for the oxide, that it decomposes the salt, combines with the iron, and assumes a yellow colour. The process recommended by Chaptal is the following. The cotton to be dyed is put into a cold solution of copperas (fulphate of iron) of the specific gravity 1.02. It is afterwards wrung out, and immediately immersed in a ley of potash of the specific gravity 1.01. This ley must have been previously saturated with a solution of alum. When the stuff has been kept for four or five hours in this bath, it may be taken out, washed and dried. By varying the proportion of fulphate of iron, every variety of shade of nankeen yellow may be obtained.

280. We shall lay before our readers another process for dyeing nankeen colour, which is proposed and followed by Mr Brewer, a practical dyer. It is as follows.

"Mix as much sheep's dung in clear water as will make it appear of the colour of grass; and dissolve in clear water one pound of best white soap for every ten pounds of cotton yarn, or in that proportion for a greater or lesser quantity.

"Observe.—The tubs, boards, and poles, that are used in the following preparations must be made of deal; the boiling pan of either iron or copper.

First Operation.—Pour the soap liquor prepared as above into the boiling pan; strain the dung liquor through a sieve; add as much thereof to the soap liquor in the pan as will be sufficient to boil the yarn, intended to be dyed, for five hours. When the liquors are Chap. I.

Of Simple Colours.

are well mixed in the pan, enter the yarn, light the fire under the pan, and bring the liquor to boil in about two hours, observing to increase the heat regularly during that period. Continue it boiling for three hours; then take the yarn out of the pan, wash it, wring it, and hang it in a shed on poles or rings. When dry, take it into a store or other room where there is a fire; let it hang there until it be thoroughly dry.

N. B. "The cotton yarn, when in the shed, should not be exposed either to the rain or sun; if it is, it will be unequally coloured when dyed.

Second Operation.—" In this operation use only one half of the soap that was used in the last, and as much dung liquor (strained as before directed) as will be sufficient to cover the cotton yarn, when in the pan, about two inches. When these liquors are well mixed in the pan, enter the yarn, light the fire, and bring the liquor to boil in about one hour; then take the yarn out, wring it without washing, and hang it to dry as in the former operation.

Third Operation.—" This operation the same as the second in every respect.

Fourth Operation.—" For every ten pounds of yarn make a clear ley from half a pound of pot or pearl-ashes. Pour the ley into the boiling-pan, and add as much clear water as will be sufficient to boil the yarn for two hours; then enter the yarn, light the fire, and bring it to boil in about an hour. Continue it boiling about an hour, then take the yarn out, wash it very well in clear water, wring it, and hang it to dry as in former operations.

N. B. "This operation is to cleanse the yarn from any oleaginous matter that may remain in it after boiling in the soap and dung liquors.

Fifth Operation.—" To every gallon of iron liquor (m) add half a pound of ruddle or red chalk (the last the best) well pulverized.

Mix them well together, and let the liquor stand four hours, in order that the heavy particles may subside; then pour the clear liquor into the boiling-pan, and bring it to such a degree of heat as a person can well bear his hand in it; divide the yarn into small parcels, about five hanks in each; soak each parcel or handful very well in the above liquor, wring it, and lay it down on a clean deal board. When all the yarn is handed through the liquor, the last handful must be taken up and soaked in the liquor a second time, and every other handful in succession till the whole is gone through; then lay the yarn down in a tub, wherein there must be put a sufficient quantity of ley made from pot or pearl-ashes, as will cover it about six inches. Let it lie in this state about two hours, then hang it over in the ley, wring it, and lay it down on a clean board. If it does not appear sufficiently deep in colour, this operation must be repeated till it has acquired a sufficient degree of darkness of colour; this done, it must be hung to dry as in former operations.

N. B. "Any degree of red or yellow hue may be given to the yarn by increasing or diminishing the quantity of ruddle or red chalk.

Sixth Operation.—" For every ten pounds of yarn make a ley from half a pound of pot or pearl-ashes; pour the clear ley into the boiling-pan; add a sufficient quantity of water thereto that will cover the yarn about four inches; light the fire, and enter the yarn, when the liquor is a little warm; observe to keep it constantly under the liquor for two hours; increase the heat regularly till it come to a scald; then take the yarn out, wash it, and hang it to dry as in former operations.

Seventh Operation.—" Make a four liquor of oil of vitriol and water: the degree of acidity may be a little less than the juice of lemons; lay the yarn in it for about an hour, then take it out, wash it very well and wring it; give it a second washing and wringing, and lay it on a board.

N. B. "This operation is to dissolve the metallic particles, and remove the ferruginous matter that remains on the surface of the thread after the fifth operation.

Eighth Operation.—" For every ten pounds of yarn dissolve one pound of best white soap in clear water, and add as much water to this liquor in your boiling-pan as will be sufficient to boil the yarn for two hours. When these liquors are well mixed, light the fire, enter the yarn, and bring the liquor to boil in about an hour. Continue it boiling slowly an hour; take it out, wash it in clear water very well, and hang it to dry as in former operations: when dry, it is ready for the weaver.

N. B. "It appears to me, from experiments that I have made, that less than four operations in the preparation of the yarn will not be sufficient to cleanse the pores of the fibres of the cotton, and render the colour permanent."

Edin.

281. A method of dyeing cotton and linen a durable yellow colour is practised in the east. The object of Proceeds following this process, which is tedious, is to increase the affinity between the alumina and the stuff, so that it may adhere with sufficient force to produce a permanent colour. For this purpose three mordants are employed: these are oil, tan and alum. The cotton is soaked in a bath of oil, mixed with a weak solution of soda. Animal oil, as it is found to answer best, is preferred. Glue has also been tried, and is found to answer very well. The soda must be in the caustic state, for in that state it combines with the oil, and produces on the cloth an equal absorption. The stuff is then to be washed, and afterwards put into an infusion of nut galls of the white kind, and the infusion should be used hot. The tan combines with the oil, while the gallic acid carries off any portion of alkali which may adhere to the cloth. When the stuff is removed from the bath, it should be quickly dried; and too great an excess of galls beyond a proper proportion with the oil should be avoided, as it is apt to darken the shade of colour. After this preparation the stuff is to be immersed in a solution of alum; and in consequence of the affinity which exists between tan and alumina, the alum is decomposed, and its earth combines with the tan. After these preliminary steps, the cotton is to be dyed with quercitron bark, according to the process which has been already described.

Sect. III.

(m) Iron liquor is what the linen printers use. Sect. III. Of Blue.

282. The next of the simple colours is blue. We shall first treat of the substances which are employed in dyeing blue, and then describe the processes which are followed in fixing this colour.

I. Of the Substances which are employed in Dyeing Blue.

The only substances which are used in dyeing blue, are indigo and woad.

283. Indigo was not used for the purpose of dyeing in Europe till near the middle of the 16th century. A substance is mentioned by Pliny*, which was brought from India, and termed indicum, which seems to have been the same as the indigo of the moderns; but it does not appear that either the Greeks or the Romans knew how to dissolve indigo, or its use in dyeing, although it was applied as a paint. It was, however, long before known as a dye in India. The first indigo which was employed for the purpose of dyeing by Europeans, was brought by the Dutch from India. One of the species of the plant from which it is obtained, was discovered by the Portuguese in Brazil, where it grows spontaneously, as well as in other parts of America. Being afterwards successfully cultivated in Mexico, and some islands of the West Indies, the whole of the indigo employed in Europe was supplied from these countries. The indigo from the East Indies has, however, of late recovered its character, and is imported into Britain in considerable quantities.

There are three species of the indigo plant, which are usually cultivated in America. The first is the indigofera tinctoria, Linn. which besides being a smaller and less hardy plant, is inferior to the others on account of its pulp, but as it yields a greater proportion, it is generally preferred. The second is the indigofera difformis, Linn. or Guatemala indigo plant. This is a taller and hardier plant, and affords a pulp of a superior quality to the former. The third is the indigofera argentea, Linn. which is the hardiest of the three species; yields a pulp of the finest quality, though in smallest proportion.

285. When the indigo plant has arrived at maturity, it is cut a few inches above the ground, chopped in strata in a large vessel or steamer, and being kept down with boards, is covered with water; and in this state it is left to ferment till the pulp is extracted. The process commences by the evolution of heat, and the emission of a great quantity of carbonic acid gas. When the fermentation has continued for a sufficient length of time, which is known by the tops becoming tender and pale, the liquor, which is now of a green colour, is drawn off into large flat vessels, called beaters, where it is agitated with buckets or other convenient apparatus, till blue floccules begin to appear. To promote this granulation or separation of the floccules it is usual to add clear lime water till the liquor in which they are suspended become quite colourless. The liquor being sufficiently impregnated with the lime water, is left at rest to allow the particles of the colouring matter to precipitate; after which the supernatant liquor is drawn off, and the sediment collected into linen bags, which are suspended for some time to let the water drain off. It is then put into square boxes, or formed into lumps and dried in the shade. The indigo thus prepared is in a state fit for the market.

286. The indigo which is produced in this operation differs greatly, not only according to the quality of the plant from which it is obtained, but according to the mode of preparation. But the difference of quality seems to depend entirely on the heterogeneous substances with which it is mixed, and on the degree of consistence which it has acquired in drying. The lightest kind which is brought from Guatemala, is called light indigo; it is of a fine blue colour, and is the most valuable, because it is of the finest quality. Indigo exhibits various shades of colour, which is also owing to the mixture of foreign substances. The most common shades are blue, violet, and copper colour.

287. Other plants have also been discovered, which is obtained by a process somewhat similar, afford indigo, and in particular the nerium tinctorium, or rose bay, an ac. plants. count of which, with the method of manufacturing indigo from its leaves, has been given by Dr Roxburgh. This tree grows in great abundance in different parts of the East Indies; and plantations of it, raised from seeds, have succeeded well in Bengal. The leaves of the nerium afford indigo, not only when they are fresh gathered, but also when they are nearly dried; but they yield the best indigo after being kept a day or two. The leaves collected the preceding day are put into a copper, so as nearly to fill it without pressing. The copper is filled with water till within three inches of the top; and hard spring water, which increases the quantity of indigo, and improves its quality, is preferred. The fire is then applied, and kept up, till the liquid becomes of a green colour in the vessel. The leaves then become of a yellowish colour, and the heat of the liquor about 150°, or 160°. The leaves should be constantly agitated, that they may be equally heated, as well as to promote the operation, by the expulsion of the carbonic acid gas. When the process exhibits the above appearances, the liquor is to be drawn off, passed through a hair-cloth, and agitated while hot, in the usual way, till granulation takes place, or the appearance of blue floccules is observed. About \( \frac{1}{3} \) part of strong lime water is then added, to promote the precipitation of the indigo, and the remaining part of the process is similar to that described above, for the manufacture of indigo from indigofera†.

288. The object of the processes which are followed in the manufacture of indigo, is to extract from the nature of plants which yield it, a green substance, which is soluble in water. This substance, which has a strong affinity for oxygen, gradually attracts it from the air, becoming of a blue colour, and is then insoluble in water. This absorption is greatly promoted by agitation, for then a greater surface is exposed to the action of the air; and the lime water, by combining with carbonic acid, which exists in the green matter, also promotes the separation of the indigo.

289. Indigo is insoluble in water, alcohol, ether, and oils, and the only acids which produce any effect of indigo upon it, are the sulphuric and nitric. By the latter it is soon changed to a dirty white colour, and is at last entirely decomposed. When the acid is concentrated, the indigo is inflamed; but when it is diluted, the indigo becomes brown, and crystals like those of oxalic and... Of Simple and tartarous acids make their appearance; and when the acid and crystals are washed off, there remains behind a kind of resinous matter. Sulphuric acid in the concentrated state dissolves indigo, with the evolution of a great deal of heat. The solution is opaque and black, but when diluted with water, it changes to a deep blue colour. Dr Bancroft has denominated this solution sulphate of indigo, which has been long known by the name of liquid blue. The fixed alkalies in the state of carbonate precipitate slowly from sulphate of indigo, a blue coloured powder, which has the properties of indigo, but is found to be soluble in most of the acids and alkalies. Pure alkalies destroy the colour of sulphate of indigo, as well as that which is precipitated.

292. Indigo is employed in dyeing, both in the state of liquid blue, or sulphate of indigo, from which is obtained the beautiful colour called Saxon blue; and also in the state of simple indigo, or the indigo of commerce. In dyeing with indigo, it must be reduced to the state of the green matter as it exists in the plants, or when it is first extracted from them. It must be deprived of the oxygen, to the combination of which the blue colour is owing. In this state it becomes soluble in water by means of the alkalies. To effect this separation of the oxygen, the indigo must be mixed with a solution of some substance which has a stronger affinity for oxygen than the green matter of indigo. Such substances are green oxide of iron and metallic sulphurates. Lime, green sulphate of iron, and indigo, are mixed together in water, and during this mixture the indigo is deprived of its blue colour, becomes green, and is dissolved, while the green oxide of iron is converted into the red oxide. In this process, part of the lime decomposes the sulphate of iron, and as the green oxide is set at liberty, it attracts oxygen from the indigo, and reduces it to the state of green matter, which is immediately dissolved by the action of the rest of the lime. Indigo is also deprived of its oxygen, and prepared for dyeing, by another process. Some vegetable matter is added to the indigo mixed with water, with the view of exciting fermentation; and quicklime or an alkali is added to the solution, that the indigo, as it is converted into the green matter, may be dissolved.

291. Another plant, known under the name of pastel or woad, (Isatis tinctoria), is employed for dyeing blue. Another species (Isatis baltica), which is a smaller plant, is also employed in dyeing. The Isatis tinctoria is cultivated in France and in England. When the plant has reached maturity, it is cut down, washed in a river, and speedily dried in the sun. It is then ground in a mill, and reduced to a paste, which is formed into heaps, covered up to protect them from the rain, and at the end of a fortnight the heap is opened, to mix the whole well together. It is afterwards formed into round balls, which are exposed to the wind and sun, that the moisture may be separated. The balls are heaped upon one another, become gradually hot, and exhale the smell of ammonia. To promote the fermentation, which is stronger in proportion to the quantity heaped up, and the temperature of the season, the heap is to be sprinkled with water till it falls down in the state of coarse powder, in which state it appears in commerce. The blue colour obtained from woad is very permanent, but has little lustre. But its colour is not only inferior in beauty to that obtained from indigo; it affords also a smaller proportion of colouring matter, so that since the discovery of indigo, the use of woad has diminished.

II. Of the Processes for Dyeing Wool Blue.

292. The preparation for dyeing blue is made in a large wooden vessel or vat, which should be so constructed as to retain the heat, which is a matter of considerable importance in the process. The vat is therefore set up in a separate place from the coppers, and is sunk so far in the ground as to be only breast-high above it. Before the introduction of indigo, blue was dyed with woad, which affords a permanent, but not a deep colour; but a very rich blue is obtained by mixing indigo with the woad, and these are almost the only substances which are now employed for dyeing woollen stuffs. The proportions of these substances are varied by different dyers, and according to the shade which is required. The following is the account of the preparation of a vat, as it is given by Quatremere. Into a vat of about seven and a half feet deep, and five and a half in diameter, are thrown two balls of pastel or woad, which are previously broken, and together amount to about 400 pounds weight; 30 pounds of weld are boiled in a copper for three hours, in a sufficient quantity of water, to fill the vat. To this decoction are added 20 pounds of madder, and a basket full of bran. The boiling is then continued half an hour longer. This bath is cooled with 20 buckets of water, and after it is settled, and the weld taken out, it is poured into the vat, which must be stirred with a rake all the time that it is running in, and for 15 minutes longer. The vat is then covered up very hot, and allowed to stand for six hours, when it is uncovered, and raked again for 30 minutes. The same operation must be repeated every three hours. When the appearance of blue streaks is perceived on the surface of the vat, eight or nine pounds of quicklime are added; the colour then becomes of a deeper blue, and the vat exhales more pungent vapours. Immediately after the lime, or along with it, the indigo, which has been previously ground in a mill, with the smallest possible quantity of water, is put into the vat. The quantity is to be regulated by the intensity of the shade required. From ten to thirty pounds may be put into a vat such as we have now described. If on striking the vat with the rake, a fine blue fume arises, no other previous preparation is required than to stir it with the rake twice in the space of six hours, to mix the ingredients completely. Great care should be taken not to expose the vat to the air, except during the time of stirring it. When that operation is finished, it is covered with a wooden lid, on which are spread thick cloths, to retain the heat as much as possible; but after all these precautions, at the end of eight or ten days it is greatly diminished, and is at last entirely dissipated, so that the liquor must be again heated, by pouring the greater part of the liquor of the vat into a copper under which a large fire is made. When the liquor has acquired a sufficient temperature, it is returned into the vat, and carefully covered up.

293. Vats of this description are sometimes liable to accidents. A vat is said to be repelled, when having to which previously afforded fine shades of blue, it appears liable to black. Of Simple Black, without any blue streaks; and if it be flirred, the black colour becomes deeper; the vat at the same time exhales, instead of a sweetish smell, a pungent odour; and the stuff dyed in a vat in this state, comes out of a dirty gray colour. These effects are ascribed to an excess of lime.

294. Different means are employed to recover a repelled vat. Some are satisfied with merely reheating it; while others add tartar, bran, urine, or madder. Hellot recommends bran and madder as the best remedy. If the excess of lime be not very great, it is sufficient to leave it at rest five or six hours, putting in a quantity of bran and three or four pounds of madder, which are to be sprinkled on the surface, and then it is to be covered up, and after a certain interval, to be tried again. But if the vat has been so far repelled as to afford a blue only when it is cold, it must be left at rest to recover, and sometimes must remain whole days without being flirred with the rake. When it begins to afford a tolerable pattern, the bath must be reheated. In general, this revives the fermentation. The addition of bran or madder, or a balkef or two of fresh wood, produces the same effect.

295. This vat sometimes runs into the putrefactive process. When this happens, the colour of the vat becomes reddish, the paste rises from the bottom, and a fetid smell is exhaled. This accident is owing to a deficiency of lime, and it must be corrected by adding a fresh quantity. The vat is then to be raked; after two hours more lime is added, and the process of raking again performed. These operations are to be repeated till the vat is recovered.

296. Nothing requires more attention in treating a vat of this kind, than the dilution of the lime, the principal use of which is to moderate the tendency to putrefaction, and to limit the fermentation to that degree which is necessary to deprive the indigo of its oxygen. If too much lime be added, the necessary fermentation is retarded, and if there be too little, the putrefactive process commences.

297. Two hours previous to the dyeing operation, the vat should be raked; and to prevent the stuff coming in contact with the sediment, which would produce inequalities in the colour, a crofs of wood is introduced. The stuff is then to be completely wetted with pure water a little heated; and being wrung out, it is dipped into the vat, where it is moved about for a longer or shorter time, according to the depth of shade required. During this operation it is taken out occasionally, to be exposed to the air, the action of which is necessary to change the green colour of the bath into a blue. Stuffs dyed blue in this manner must be carefully washed, to carry off the loose particles of colouring matter; and when the shade of blue is deep, they ought even to be cleansed, by fulling with soap. This operation does not alter the colour.

298. When a vat is prepared entirely of indigo, without pastel or woad, it is called an indigo vat. The vessel employed for this purpose is of copper, into which water is poured, according to its capacity, to the amount of 40 buckets, in which have been boiled six pounds of potash, twelve ounces of madder, and six pounds of bran. Six pounds of indigo ground in water are then put in, and after it has been carefully raked, the vat is to be covered. A slow fire is to be kept up, and twelve hours after it is filled, it is to be raked a second time. This operation is to be repeated every twelve hours, till it come to a blue colour, which will generally be the case in about 48 hours. If the bath is properly managed, it will be of a fine green, exhibiting on the surface coppery scales, and a blue scum or flower. In this vat the indigo is rendered soluble in water, by means of the alkali instead of lime. The dyeing operation is to be conducted in the same manner as the preceding.

299. Two vats have been described by Hellot, in Hellot's which the indigo is dissolved by means of urine. Madder is added to it, and in the one vinegar, in the other alum and tartar, of each a quantity equal in weight to that of the indigo. The proportion of urine must be considerable. In considering the theory of this process, it seems probable that the indigo, deprived of its oxygen by the urine and madder during the fermentation, is dissolved by the ammonia which is formed in the urine. When the solution of alum and tartar is added, an effervescence, which Hellot observed, is produced. This, it is probable, has a tendency to retard or stop the putrefaction. But in vats of this description, operations on a large scale cannot be carried on; they seem only adapted for small dye-houses.

III. Of the Processes for Dyeing Silk Blue.

300. Silk is dyed blue with indigo alone, without any proportion of woad. The proportion of indigo mentioned in the preparation of the indigo vat, and sometimes a larger proportion, is employed, with six pounds of bran, and about twelve ounces of madder. According to Macquer, half a pound of madder for each pound of potash, renders the vat greener, and produces a more fixed colour in the silk. When the vat is come to, it should be refreshed with two pounds of potash, and three or four ounces of madder; and after being raked in the course of four hours, it is fit for dyeing. The temperature should be moderated, that the hand may be held in it without uneasiness.

301. The silk, after being boiled with soap, in the proportion of 30 pounds of soap to 100 of silk, and of the silk well cleaned by repeated beatings in a stream of water, must be dyed in small portions, because it is apt to take on an uneven colour. When it has been turned once or oftener in the bath, it is wrung out, and exposed to the air, that the green colour may change to a blue. When the change is complete, it is thrown into clear water, and afterwards wrung out. Silk dyed blue should be speedily dried. In damp weather and in winter, it is necessary to conduct the drying in a chamber heated by a stove. The silk should be hung on a frame kept constantly in motion. To dye light shades, some dyers employ vats that are somewhat exhausted; but it ought to be observed, that the colour thus obtained is less beautiful and less permanent than when fresh vats, containing a smaller quantity of indigo, are employed.

302. Some addition is required to be made to the indigo, to give silk a deep blue. A previous preparation is necessary, by giving it another colour or ground. For the Turkey blue, which is the deepest, a strong bath of archil is first prepared. Cochineal is also sometimes used, instead of archil, for the ground, to render the colour more permanent. A blue is given to silk Of Simple silk by means of verdigris and logwood, but it possesses little durability. It might be rendered more permanent, by giving it a lighter shade in this bath, then dipping it in a bath of archil, and finally in the indigo vat.

Dyeing raw silk. 303. When raw silk is to be dyed blue, such as is naturally white should be selected. Being previously soaked in water, it is put into the bath in separate hanks, as already directed for scoured silks; and as raw silk is found to combine more readily with the colouring matter, the scoured silk, when it can be conveniently done, should be first put into the bath. If archil, or any of the other ingredients which have been already mentioned, are required, to give more intensity to the colour, the mode of application is the same as that directed for scoured silk.

IV. Of the Processes for Dyeing Cotton and Linen Blue.

Preparation. 304. For dyeing cotton and linen blue, Pileur of the vat. d’Aphigny recommends a vat containing about 120 gallons. From six to eight pounds of indigo reduced to powder, are boiled in a ley drawn off from a quantity of lime, equal in weight to the indigo, and a quantity of potash double its weight. During the boiling, which is to be continued till the indigo is completely penetrated with the ley, the solution must be constantly stirred, to prevent the indigo from being injured, by adhering to the bottom of the vessel.

305. During this process, another quantity of quicklime, equal in weight to the indigo, is to be flaked. Twenty quarts of warm water are added, in which is to be dissolved a quantity of copperas (sulphate of iron) equal to twice the weight of the lime. The solution being completed, it is poured into the vat, which is previously half filled with water. To this the solution of indigo is added, with that part of the ley which was not employed in the boiling. The vat must now be filled up to within two or three inches of the top. It must be raked twice or thrice a day till it is completely prepared, which is generally the case in 48 hours, and sometimes sooner, as it depends on the temperature of the atmosphere. A small proportion of bran, madder, and woad, is recommended by some, to be added to such a vat as we have now described.

306. The process which is followed at Rouen, and described by Quatremere, is simpler. The vats, which are constructed of a kind of flint, are coated within and without with fine cement, and are arranged in one or more parallel lines. Each vat contains four hogsheads of water. The indigo, to the amount of 18 or 20 pounds, being macerated for a week in a cauldron, strong enough to bear an egg, is ground in a mill; three hogsheads and a half of water are put into the vat, and afterwards 20 pounds of lime. The lime being thoroughly flaked, the vat is raked, and 36 pounds of copperas are added; and when the solution is complete, the ground indigo is poured in through a sieve. It is raked seven or eight times the same day, and after being left at rest for 36 hours, it is in a state fit for dyeing.

Process on a larger scale. 307. In extensive manufactories, it is necessary to have vats set at different times. In conducing the processes of dyeing, the stuffs are first dipped in the most exhausted vat, and then regularly proceeding from the weakest to the strongest, if they have not previously attained the desired shade. The stuffs should remain in the bath only about five or six minutes, for in that time they combine with all the colouring matter they can take up. After the stuffs have been dipped in a vat, it should not be used again, till it has been raked, and stood at least 24 hours, unless it has been lately set, when a shorter period is sufficient.

308. After the stuffs have been dipped three or four times in a vat, it begins to change. It becomes black, and no blue or copper-coloured streaks are seen on the surface after raking it. It must then be renewed, by adding four lbs. of copperas, with two of quicklime, after which it must be raked twice. In this way, a vat may be renewed three or four times; but the additional quantity of ingredients must be diminished, as the strength of the vat is exhausted.

309. A vat which is still more simple, and more easily prepared, has been recommended by Bergman. The proportion of the ingredients which he has directed to be employed, is the following. To three drachms of indigo reduced to powder, three drachms of copperas, and three of lime, add two pints of water. Let it be well raked, and in the course of a few hours it will be in a proper state for dyeing.

310. Hauffman employs still a smaller proportion of Hauffman’s indigo. For 3000 lbs. of water he takes 36 lbs. of quicklime flaked in 200 lbs. of water, with which the indigo in the proportion of from 10 to 20 lbs. wellground, is to be mixed. He then dissolves 30 lbs. of copperas in 120 lbs. of hot water. The whole being left at rest for fifteen minutes, the vat is filled, and gently and constantly stirred. When a deeper shade is wanted, and particularly when linen is to be dyed, the proportion of indigo should be greater; but the shade depends very much on the time the stuffs remain in the vat, and the times it has been used. When the vat becomes turbid, the process of dyeing must be interrupted, till it has been again raked, and the supernatant liquor become transparent. If the effects of the lime fail, a new quantity fresh flaked, must be added; and if the iron cease to produce the effect on the indigo, a new portion must be also added, observing the precaution to have a greater quantity of lime than what is necessary to saturate the sulphuric acid. When the indigo seems to be exhausted, fresh portions ground in water are also to be added; the vat is to be raked several times, and allowed to settle, after which it is again fit for use. In this way Mr Hauffman informs us he preferred a vat for the space of two years; and had it not been for the accumulation of sediment, which prevented the stuffs from being immersed to a sufficient depth, it might have been continued in use for a much longer time. It is worth while to add, that Mr Hauffman found, that a pattern of cloth dipped in water, acidulated with sulphuric acid, immediately after it was taken out of the bath, became of a much deeper blue than a similar pattern exposed to the air, or another dipped in river water.

311. Another convenient and expedient vat is mentioned by Bergman, and described by Scheffer. Indigo reduced to fine powder, in the proportion of three drachms to a quart, is added to the strong ley of the soap-boiler. After a few minutes, when the colouring matter is well penetrated by the ley, fix drachms of powdered orpiment are to be added. In a few minutes after the bath has been well raked, it becomes green, Of simple and the blue streaks appear on the surface. Heat is to be applied; when the operation of dyeing may commence.

312. The preparation employed for printing cottons is similar to the above bath, excepting in the proportions of orpiment and indigo, which are greater in the former; but these proportions are very different in different manufactories.

313. Saxon Blue.—The colour which is obtained by dyeing with a solution of indigo in sulphuric acid is known under the name of Saxon blue, because the process was first carried on at Großenhain in Saxony, by Counsellor Barth, who made the discovery about the year 1740. This discovery was for some time kept secret, and the method seems to have been originally very complicated. Alumina, antimony, and some other substances, were previously added to the sulphuric acid. These, however, are now omitted, and the indigo alone is dissolved in the acid.

314. From a great number of experiments which were made on this process by Bergman, he concluded, that in those cases where the sulphate of indigo afforded only a fading colour, the acid employed had been too weak. Quatremere observes that, among several processes for dyeing with sulphate of indigo, he discovered only two, in which the stuffs were completely penetrated with colouring matter. To effect this, he employed an alkali, in the proportion of one ounce to an ounce of indigo, and six ounces of sulphuric acid. With these proportions of the ingredients he obtained a deep vivid blue, equally intense through every part of the stuff. Poerner, who has paid great attention to this preparation, also employs an alkali, by means of which a more pleasing colour, which penetrates deeper, is produced. The proportions which he recommends are four parts of sulphuric acid to one of indigo. The indigo is first reduced to a fine powder, and the sulphuric acid, in the concentrated state, is poured upon it. The mixture is stirred for some time, and having stood twenty-four hours, one part of dry potash in fine powder, is added; and after the whole is again stirred, it remains for twenty-four hours longer. It is then to be diluted with eight times its weight of water, which must be gradually added, or a greater or less proportion as may be wanted.

Dr Bancroft seems to be of opinion, that a more durable blue may be obtained by diluting the acid with an equal quantity of water, when the indigo is put in, and allowing the mixture to remain forty-eight hours; for he thinks by this slower and more moderate action, the basis of the indigo is less injured. Instead of the potash employed by Poerner, Dr Bancroft uses chalk; and even in such a quantity as to saturate the acid. In this case the indigo is precipitated along with the chalk; and, when collected into a solid mass, communicates a blue colour to wool, but more slowly than by the common method, in which the combination is very rapid and the dyeing unequal. This inconvenience he thinks might be obviated by the use of chalk.

315. To produce a Saxon blue colour on woollen stuffs, they are prepared with alum and tartar. And in proportion to the shade required, the quantity of solution of indigo put into the bath must be regulated. When a deep shade of Saxon blue is wanted, the stuff must be passed different times through vessels containing such a quantity of colouring matter as is sufficient to give light colours. In this way, by repeated applications, the colour becomes more uniform.

316. The sulphate of indigo is also employed to dye silk. For this purpose attempts have been made to unite the advantages of the indigo vat and its solution in sulphuric acid. A process of this kind is greatly recommended by Gublache, which produces beautiful colours, and is at the same time cheap and convenient. The bath is composed of one pound of indigo, three pounds of quicklime, three of copperas, and one and a half of orpiment. The indigo is first to be carefully ground and mixed with water, put into a wooden vat, and diluted with water, according to the shade of colour wanted. The lime is then to be added, and the mixture being well stirred, it is covered up, and allowed to remain at rest for some hours. After this the copperas in the state of powder is added, the whole well stirred, and the vat covered up. And lastly, at the end of some hours, the orpiment reduced to powder is thrown in, and the whole left at rest for several hours. The mixture is afterwards to be stirred, and then left to settle, till the liquor becomes clear; when the blue streaks or flower which covers it is removed, and the silk previously dipped in warm water, is to be dyed hank by hank. When it is removed from the bath, it is to be washed in a stream of water, and dried.

317. This process is recommended as the means of obviating a greenish cast, which is sometimes observed in Saxon blue, and which is supposed to be owing to some change in the particles of indigo, by means of the sulphuric acid.

318. The colour denominated English blue is produced by means of the sulphate of indigo. To give blue silk this colour, it is first to be dyed a light blue; and, when taken out of this bath, it is dipped in hot water, washed in a stream, and left in a bath composed of the sulphate of indigo, to which a little of the solution of tin has been added, until the proper shade is obtained, or the bath is exhausted. Previous to its being put into this bath, it may be dipped in a solution of alum, in which it should only remain a very short time. Silk, which has been dyed according to this process, is free from the reddish tinge which it derives from the blue vat, as well as from the greenish cast of the Saxon blue.

319. The sulphate of indigo has been hitherto only applied for the purpose of dyeing wool and silk. The affinity of indigo for vegetable substances is not sufficiently strong to effect the decomposition of the sulphate. It cannot, therefore, be employed with advantage in dyeing cotton and linen.

320. Attempts have been made to dye with Prussian Dyeing blue. The process which was followed by Macquer is with prussiate of iron, the following. He soaked wool, silk, cotton, and tan blue thread, in a solution of alum and sulphate of iron, and afterwards in an alkaline solution, which was partly saturated with prussic acid. He then immersed the stuffs in water, acidulated with sulphuric acid, for the purpose of dissolving that part of the oxide of iron which remained uncombined with the prussic acid, and which the uncombined alkali had precipitated. By successive repetitions of these immersions he obtained a fine blue, but very unequal. Berthollet justly remarks on this experiment. Of Simple experiment, that an alkali saturated with prussic acid should be employed, or lime water or magnesia, both of which have the property of combining with that acid. In a second experiment Macquer boiled the stuffs in a solution of tartar and alum, and then passed them through a bath which contained the prussian blue merely diffused in it. The colour was faint, and could not be made deeper; but it was equal, and soft to the touch.

321. In the process proposed by Abbé Menon for thread and cotton, they are first dyed black, and soaked for a few minutes in prussiate of alkali, and afterwards boiled in a solution of alum. In this way they acquired a deep blue. When a lighter blue is wanted, the stuffs must be passed through a weak acid.

322. Similar to the second experiment of Macquer is the process of Roland de la Platière. He takes prussian blue in the proportion of a pound to a piece of stuff, powdered, and passed through a very fine sieve, and adds muriatic acid till it is reduced to the consistence of syrup. It is to be constantly stirred for about half an hour, while it ferments. It is then well diluted, and stirred every hour for a day, till the fermentation ceases. The particles are thus in a state of minute division. Seven or eight buckets of water for one piece of velvet, are put into a trough; then add the mixture, which has been previously well diluted in a separate vessel, and poured into the bath through a very fine sieve. When the piece is placed on the winch, over the trough, let the bath be briskly stirred, and the piece speedily let down; and the same operation must be continued as quickly as possible for several hours. This colour requires great management, for as the particles of the prussian blue are only in a state of minute division, and heavy, they are quickly deposited on the stuff. Hence the colour appears very unequal and in patches, even with the utmost care; and nothing can be done to avoid it, but repeating the operations again and again. The stuff should be put into the baths thoroughly wet, for when it is dry, it penetrates with difficulty, and is always unequal. Between the dryings the stuff is always to be washed and beatled, excepting the last time, when it is not washed, but dried in the open air, either in the sun or in the shade; observing however, that it be well stretched. This beautiful colour is not changed by the air; it resists the action of acids, and is little altered by boiling with alum; but it is soon tarnished by friction, or particles of dust that adhere to it. It is scarcely necessary to add, that it is instantly decomposed by alkaline liquids. Guhlische employs a solution of tin in nitro-muriatic acid, as a substitute for muriatic acid, in the process of dyeing with prussian blue.

323. Dr Bancroft made a number of experiments in dyeing both vegetable and mineral matters, with prussian blue, and particularly with the view of obviating the difficulties which had occurred to others in the use of it. He boiled up copperas with quercitron bark, fustic, and logwood, separately, in what he thought the best proportions; and in each of these mixtures he dyed a piece of woollen cloth by boiling it for 10 or 15 minutes. The stuffs were afterwards separately immersed in warm diluted prussiate of potash neutralized by sulphuric acid. They acquired an equal and beautiful blue. This however, was not the uniform result; for when too much copper as was employed in dyeing with quercitron bark, there was an excess of oxide of iron, which combining with the fibres of the wool, gave the prussian blue a greenish tinge; but this he found could be remedied, by passing the cloth through warm water, slightly acidulated with muriatic acid. The prussian colouring matter, Dr Bancroft observes, must always be applied in a moderate heat, otherwise it will be precipitated by the sulphuric acid, and rendered unfit for this purpose, till it is again dissolved by potash, lime, or some other substance.

324. He then tried to fix prussian blue by means of the aluminous mordant, but at the end of 15 minutes, after being immersed in a solution of prussiate of potash, it had acquired no colour. The addition of a small proportion of a solution of iron in muriatic acid, communicated a blue colour. All parts of the cloth, as well as those to which the mordant had been applied, received the colour. The cloth being washed with soap, the whole of the colour was discharged, excepting where it had been impregnated with alumina, and even there it had become fainter. A piece of the same cotton was immersed in a solution of ammonia (volatile alkali); the pale blue was greatly heightened. Another piece was put into water slightly tinged with a solution of copper in ammonia. The blue colour became suddenly of an intensely deep garter-blue or violet, and it resisted the action of soap. Into water mixed with a little of a solution of muriate of copper, he put another piece of the same cotton, and it soon became of a deeper blue, without any of the purple or violet shade. This resisted the action of soap, and after long exposure to the weather, the colour was little diminished; and when the colour remained in any degree weakened, immersion in water slightly acidulated with fulphuric acid, completely restored it. From these facts it would appear to be advantageous to prepare woollens by the usual boiling with alum, or alum and tartar, before they are dyed with copperas and quercitron bark, fustic or logwood, for a prussian blue; but a greater proportion of sulphuric acid, in the prussiate of potash or lime, that the excess of acid may discharge the vegetable colouring matters becomes necessary.

325. Dr Bancroft afterwards tried pieces of silk and cotton in the diluted prussiates of potash, soda, lime, &c., with solutions of most of the metals in different acids and alkalis; and from the different metallic solutions he obtained a very full, lively colour, which he calls the red copper colour; from the different solutions of copper in fulphuric, nitric, muriatic, and acetic acids; the same effect succeeded well from a solution in ammonia. He obtained also the same colour from the nitrates of silver and of cobalt. The prussian colouring matter fixed by these metallic mordants resisted the action of acids, washings with soap, and exposure to the weather for the greatest length of time; but in all these cases there must be a double application. The prussian colouring matter must first be applied to the linen, cotton or silk, which must be afterwards allowed to dry. It must then be immersed in the metallic solution, or the metallic solution must be applied first, and then the solution of prussiate of potash, soda, lime, &c.

Sect. IV. Of Dyeing Black.

The next of the simple colours is black, of which we shall treat as in the former sections; first describing the substances which are employed, and then giving an account Of Simple account of the processes which are followed in dyeing different stuffs of a black colour.

I. Of the Substances employed in Dyeing Black.

326. There are few substances which have the property of producing a permanent black colour, without any addition. The juice of some plants produces this effect on cotton and linen. A black colour is obtained from the juice of the cashew nut, which will not wash out, and even resists the process of boiling with soap or alkalies. The cashew nut of India is employed for marking linen. That of the West Indies (Anacardium occidentale, Lin.) also yields a permanent dye, but the colour has a brownish shade. The juice of some other plants, as that of the toxicodendron, or floes, affords a durable blueish black colour; but these substances cannot be obtained in sufficient quantity, even if they afforded colours equal to those produced by the common processes.

327. The principal substances which are employed to give a black colour are gall nuts which contain the astringent principle, or tan, and the red oxide of iron (r). For a particular account of the nature and properties of tan, see Chemistry Index. The black colour is produced by the combination of the astringent principle with the oxide of iron, held in solution by an acid, and fixed on the stuff. When the particles are precipitated from the mixture of tan and a solution of iron, they have only a blue colour; but after they are exposed for some time to the air, and moistened with water, the colour becomes deeper, although the blue shade is still perceptible. After the particles are fixed on the stuff, the shade becomes much deeper.

328. Logwood is not to be considered as affording a black dye, but is much employed to give a lustre to black colours. We have (180,) already described its nature and properties, among the substances from which red colouring matters are obtained.

329. Black colours are rarely produced by a simple combination between the colouring matter and the stuff; but are usually fixed by means of mordants, as in the case of the black particles which are the result of a combination of the astringent principle and the oxide of iron, held in solution by an acid. But when the particles are precipitated from the mixture of an astringent and a solution of iron, they have only a blue colour. By being exposed to the air, and moistened with water, the colour becomes deeper, although the blue shade is still perceptible. No fine black colour is ever obtained, unless the stuffs are freely exposed to the air. In dyeing black, therefore, the operations must be conducted at different intervals. Berthollet has observed that black stuffs, when brought in contact with oxygen gas, diminish its volume, so that some portion of it is absorbed.

II. Of the Processes for Dyeing Woollen Black.

330. In dyeing woollen stuffs black, if a full and fine deep colour is wanted, it is necessary that they are pre-dyed blue. To remove all the particles of colouring matter which happen to be loosely attached to the stuff, it should be washed in a river as soon as it is taken out of the vat, and afterwards cleansed at the fulling mill. After these preliminary processes, the stuffs are ready to receive the black colouring matter. The process of Hellot is the following:

For every hundred pounds of stuff, ten pounds of log-Hellot's wood, and ten pounds of galls reduced to powder, are procured, put into a bag and boiled in a middle-sized copper, with a sufficient quantity of water, for 12 hours. A third of this bath is put into another copper, along with two pounds of verdigris. The stuff is immersed in this bath, and continually stirred for 2 hours. The bath should be kept hot, but it ought not to boil. At the end of two hours the stuff is taken out, and a similar portion of the bath is put into the copper, with eight pounds of copperas (sulphate of iron). During the solution of the copperas, the fire is diminished, and the bath is allowed to cool for half an hour, stirring it well the whole time. The remainder of the bath is then to be added, and after making this addition, the bag containing the astringent matters should be strongly pressed, to separate the whole. A quantity of sumach from 15 to 20 pounds, is now to be added, and the bath is just raised to the boiling temperature; and when it has given one boil, it is to be immediately dropped with a little cold water. A fresh quantity of sulphate of iron, to the amount of two pounds, is then added, and the stuff is kept in it for another hour, after which it is taken out, washed and aired; it is again put into the copper, and constantly stirred for an hour. It is then carried to the river, well washed, and fulled. To soften the black colour, and make it more firm, another bath is prepared with weld. This is made to boil for a moment, and when it has cooled, the stuff is passed through it. By this process, which is indeed somewhat complicated, a beautiful black colour is produced.

331. But the processes usually followed for dyeing common black, are more simple. Cloth which has been pre-process, violently dyed blue, is merely boiled in a vat of galls for two hours. It is then kept two hours, but without boiling, in the bath of logwood and sulphate of iron, and afterwards washed and fulled. According to Hellot's process, a bath is to be prepared of a pound and a half of yellow wood, five pounds of logwood, and ten pounds of sumach, which is the proportion of the ingredients.

(r) Oak bark has been recommended as a substitute for gall-nuts in dyeing black, and particularly in dyeing hats; and it is said that the colour thus obtained is fuller, more beautiful and durable, while the operation is easier and less liable to accident. It was first proposed in the year 1782 by Stephanopoli, a Corfican, and a surgeon in the French army. The examination of the process was referred by the French government to Macquer, who gave a favourable report of it; and afterwards to Berthollet, who gave a different opinion. The process has since been examined, and promises to be more economical and advantageous, especially for dyeing hats. Of Simple Colours.

332. When fluffs are to be dyed at a less expense, instead of the blue ground, a brown or root-coloured ground may be substituted. This brown or fawn colour is communicated by means of the root of the walnut tree, or green walnut peels. The fluffs are then to be dyed black, according to some of the processes already described.

333. The proportions of the ingredients employed by the English dyers are, for every hundred pounds of cloth previously dyed a deep blue, about five pounds of sulphate of iron, five pounds of galls, and 30 of logwood. The first step in the process is to gall the cloth, after which it is passed through the decoction of logwood, to which the sulphate of iron has been added.

334. The leaves of the arbutus unedo have been recommended, and employed as a substitute for galls. The leaves must be carefully dried, so that the green colour may be preserved. A hundred pounds of wool are boiled with 16 pounds of sulphate of iron, and eight of tartar, for two hours. The day following the cloth is to be rinsed as after aluming. A hundred and fifty pounds of the leaves of unedo are then to be boiled for two hours in water, and after being taken out, a small quantity of madder is to be added to the liquor, putting in the cloth at the same time, which is to remain about an hour and a half. It is then taken out and rinsed in water. By this process, it is said, blue cloth receives a pretty good black, but white cloth becomes only of a deep brown. It is said, too, that the madder and tartar are useless ingredients.

335. After the different operations for dyeing the cloth have been finished, it is washed in a river, and fulled, till the water comes off clear and colourless. Soap lads are recommended by some in fulling fine cloths, but it is found difficult to free the cloth entirely from the soap. After the cloth has come from the fulling mill, some propose to give it a dip in a bath of weld, by which it is said to be softened, and the colour better fixed; but according to Lewis, this operation, which in other cases is of some advantage, is useless after the cloth has been treated with the soap suds.

III. Of the Processes for Dyeing Silk Black.

336. In communicating a black colour to silk, different operations are necessary, such as boiling, galling, repairing the bath, dyeing, and softening.

337. To give a deeper shade to silk, it is necessary to deprive it of the gummy substance to which its stiffness and elasticity are owing. This is done by boiling the silk four or five hours with one fifth its weight of white soap, and afterwards beating and carefully washing it.

Galling.

338. In conducting the process of galling silk, three fourths of its weight of galls are to be boiled for three or four hours, but the proportion of galls must depend on their quality. After the boiling, the liquor is allowed to remain at rest for two hours; the silk is then put into the bath, and left there from 12 to 36 hours, when it is to be taken out, and washed in the river. But as silk is capable of combining with a great proportion of the altrigent principle, or tan, from which it receives a considerable increase of weight, it is allowed to remain for a longer or shorter time, as the silk is required to have more or less additional weight. To communicate, therefore, to silk what is called a heavy black, it is allowed to remain longer in the gall liquor; the process is repeated oftener, and the silk is also dipped in the dye a greater number of times.

339. While silk is preparing for the process of dyeing, the bath is to be heated, and should be occasionally stirred, that the grounds which fall to the bottom may not acquire too much heat. It should always be kept under the boiling temperature. Gum and solution of iron are added in different proportions, according to the different processes. When the gum is dissolved, and the bath near the boiling temperature, it is left to settle for about an hour. The silk, which in general is previously divided into three parts, that each may be successively put into the bath, is immersed in it. Each part is then to be three times wrung, and after each wringing hung up to air. The silk being thus exposed to the action of the air, acquires a deeper shade. This operation being finished, the bath is again heated, with the addition of gum and sulphate of iron, and this is repeated two or three times, according as the black required is light or heavy. When the process of dyeing is finished, the silk is rinsed in a vessel with some cold water, by turning or shaking it over.

340. Silk, after it has been taken out of the dye, is softened extremely harshly, to remove which it is subjected to the operation of softening. A solution of four or five pounds of soap for every hundred pounds of silk, is poured through a cloth into a vessel of water. The solution being completed, the silk is immersed, and allowed to remain in it for about 15 minutes; it is then to be wrung out and dried.

341. When raw silk is to be dyed, that which has a natural yellow colour is preferred. The galling operation must be performed in the cold, if it be proposed to preserve the whole of the gum, and the elasticity which it gives to the silk; but if part only of the gum is wished to be preserved, the galling is to be performed in the warm bath.

342. The dyeing operation is also performed in the cold. All that is necessary is to add the sulphate of iron to the water in which the stuff is rinsed. By this simple process the black dye is communicated. It is then washed, once or twice beetleed, and dried without wringing, that its elasticity may not be destroyed. Raw silk may be dyed by a more speedy process. After a speedier galling, it may be turned or thicken over in the cold bath; and thus by alternately dipping and airing the stuff, the operation may be completed. It is then to be washed and dried as in the former processes.

343. The method of dyeing velvet at Genoa, which has been simplified and improved in France, is thus described by Macquer. For every 100 pounds of silk velvet: 20 pounds of Aleppo galls, reduced to powder, are boiled in a sufficient quantity of water for an hour. The bath is allowed to settle till the galls have fallen to the bottom; they are then taken out, and two pounds and a half of sulphuric acid, twelve pounds of iron filings, and 20 pounds of gum, are put into a copper This vessel is immersed in the bath, and supported that it may not touch the bottom. The gum, which is allowed to dissolve for an hour, is to be occasionally stirred; and if it appear that the whole of the gum is dissolved, three or four pounds more are to be added. Excepting during the operation of dyeing, the cullender is to remain in the copper, which must be kept hot the whole time, but at a temperature below the boiling point. In galling the silk, one-third of Aleppo galls is employed, and the stuff should remain five hours in the liquor the first time, and twelve hours the second. By frequent additions of sulphate of iron, and repeated immersions of the stuff, a fine black, according to Lewis, has been obtained. In the above process, the proportion of sulphate of iron is too small, and the gum, according to some, being carried off in the washing, may be considered as useless. Berthollet thinks that, although the quantity be excessive, it has some effect in keeping up the bath, and he adds, if it is to be diminished, it would be useful to add the sulphate of iron in separate portions during each interval.

344. To diminish the quantity of galls, which are an expensive ingredient in dyeing silk black, other substances have been proposed as substitutes. With this view the following process is recommended.

The silk being boiled and washed, is immersed in a strong decoction of green walnut peels, and allowed to remain till the colouring matter of both is exhausted. It is then to be slightly wrung out, dried and washed (m). To give the silk a blue ground, logwood and verdigris are employed, in the proportion of one ounce of the latter for every pound of silk. The verdigris is dissolved in cold water, and the silk is allowed to remain two hours in this solution. It is then immersed in a strong decoction of logwood, slightly wrung out, dried, and afterwards washed at the river. The bath is prepared by macerating two pounds of galls and three of fumach in 25 gallons of water, over a slow fire, for twelve hours. The liquid being strained, three pounds of sulphate of iron, and the same quantity of gum arabic, are to be dissolved in it. The silk is dipped in this solution at two different times; it is to remain in the bath two hours each time, and it must be aired and dried between each dip. After being twice beatled at the river, it is dipped a third time, and left in the bath four or five hours, after which it is to be dried, washed and beatled as before. The temperature of the bath should not exceed 120°. After the first dipping, it may be necessary to add half a pound of sulphate of iron, and an equal quantity of gum arabic.

345. Silk which has been previously dyed blue with indigo, it is said, takes only a mealy black; but when it has been prepared with logwood and verdigris, it acquires a velvety lustre. A fine black may be obtained from green walnut peel; but the addition of logwood and verdigris renders a smaller quantity of sulphate of iron necessary, and this is of importance, because it is apt to weaken the silk. The only use of galls, according to some, is to increase the weight of the silk; for the purposes of dyeing, fumach is considered sufficient.

IV. Of the Processes for Dyeing Cotton and Linen Black.

246. It is more difficult to communicate a fine black stuff to linen or cotton than to silk or woollen stuffs. To previously succeed in producing a black colour of that degree of blue intensity which will resist soap, it is necessary to adopt particular processes. In dyeing animal matters black, as silk, and wool, the best colours are obtained on those which have been previously dyed blue. This also is an essential preliminary process in dyeing linen and cotton black; for it is found that the process which succeeds best, is first to give a deep blue grain to the cotton or linen.

347. The first part of the process is the operation of Galling. The stuffs which have been previously dyed blue, wrung out and dried, are kept 24 hours in the gall-liquor, composed of four ounces of galls to every pound of thread. A bath is then prepared of a solution of iron in acetic acid. This solution is obtained by saturating the acid with oxide of iron. In France, vinegar, small beer, or small wine, is employed for this purpose. To promote the acid fermentation, rye meal, or some other substance, is added, and pieces of old iron are thrown into the liquid, which are allowed to remain for six weeks or two months, that the acid may be saturated with the iron. This solution, called iron liquor in this country, is prepared from fermented worts, to which old iron is added, as is described above. Five quarts of the iron-liquor for every pound of stuffs, dyeing, are put into a vessel. In this the stuffs are wrought with the hand, pound by pound, for 15 minutes: they are then wrung out and aired. This operation is to be again repeated, taking care to add a fresh quantity of the iron-liquor, which should be carefully scummed, after which the stuffs are to be wrung out, aired, and washed at the river. In the next operation, a pound of alder bark for every pound of stuff is boiled in a sufficient quantity of water for an hour. One half of the bath which was employed in the galling, and about one half the quantity of fumach as of alder bark, are then added. The whole is boiled together for two hours, and strained through a sieve. When this liquid is cold, the stuffs are immersed, wrought pound by pound, and occasionally aired. They are afterwards put into the bath, and after remaining for 24 hours, are wrung out and dried. The above is the process which, according to D'Apligny, is followed at Rouen, for dyeing cotton and linen.

348. The process followed at Manchester, which is another described by Mr Wilton, is the following. For the process of operation of galling, galls or fumach are employed. The stuff is afterwards dyed in a bath consisting of a solution of iron in acetic acid. This bath is also frequently composed of alder bark and iron. After having passed through this bath, the stuff is dipped in a decoction of logwood, to which a small quantity of verdigris has been added. This process is to be repeated.

(m) The decoction of walnut peels is prepared by boiling for 15 minutes, after which it is taken from the fire. After it has subsided, the silk, which has been previously immersed in warm water, is dipped in it. Chap. I.

Of Simple Colours.

Preparation of solution of iron.

According to Gubliehe, a solution of iron may be prepared by the following process. A pound of rice is to be boiled in 12 or 15 quarts of water, till the whole is dissolved. A sufficient quantity of old iron made red hot, to reach half way to the surface of the liquor, is thrown into the solution. The vessel in which the solution is kept must be under cover, but exposed to the air and light at least for a week. In another vessel, containing a quantity of warm vinegar equal to the solution of rice, an equal quantity of red-hot iron is to be put. This vessel must also be exposed in the same way to the air and light. After several days, the contents of both vessels are mixed together, and the mixture is to be exposed for a week to the open air, after which it is to be decanted and kept for use in a clothe vessel. To give a sufficient black to linen and cotton, it is only necessary, it is said, to steep them 24 hours in this solution; and if it should appear that the liquor is exhausted of colouring matter, a fresh portion is to be employed. In this way a fine permanent black is obtained. According to the same author, this solution may be advantageously employed as a substitute for sulphate of iron, in dyeing silk and wool. But to give them a fine black, silk and woollen stuffs must be dipped in a decoction of logwood after they are taken from the bath.

Sect. V. Of Brown.

350. The last of the simple colours is brown. This is also known under the name of fawn colour, (fauve, Fr.) It is that brown colour which has a shade of yellow, and might perhaps be considered as a compound colour, although it is communicated to flax by one process.

I. Of the Substances employed in Dyeing Brown.

351. The vegetable substances which are capable of inducing a fawn or brown colour on different stuffs, are very numerous, but those chiefly employed for this purpose are walnut peels and sumach. The peels constitute the green covering of the nut; they are internally of a white colour, which is converted into brown or black by exposure to the air. The skin when impregnated with the juice of walnut peels, becomes of a brown or almost black colour. When the inner part of the peel, taken fresh, is put into weak oxymuriatic acid, it affumes a brown colour. If the decoction of walnut peels be filtered and exposed to the air, its colour becomes of a deep brown; the pellicles on evaporation are almost black; the liquor detached from these yields a brown extract completely soluble in water. The colouring particles are precipitated from a decoction of walnut peels, by means of alcohol, and they are soluble in water. No apparent change is at first produced by a solution of potash; but it gradually becomes turbid, and the colour is deepened. A copious precipitate of a fawn colour, approaching to an ash colour, is produced in a decoction of walnut peels by means of a solution of tin, and the remaining liquor has a slightly yellow tinge.

352. A decoction of walnut peels yields a small quantity of fawn-coloured precipitate by means of a solution of alum, and the liquor remains of the same colour. Sulphate of copper renders it slowly turbid, and throws down a small quantity of precipitate of a brownish green colour, leaving the supernatant liquor of the same colour. Sulphate of iron deepens the colour; when diluted, the colour becomes brownish green, without the deposition of any sediment. Sulphate of zinc also deepens the colour, and produces no precipitate. The same properties are exhibited by a decoction of the walnut-tree wood, but the colouring matter is not obtained from it in such abundance as from the peels; and the bark may also be used with advantage in dyeing.

353. The affinity of the colouring matter of walnut peels for wool is very strong; and it readily imparts to it a durable colour, which even mordants do not seem capable of increasing, but they are generally understood to give it additional brightness. A lively and very rich colour is obtained with the assistance of alum. Walnut peels afford a great variety of pleasing shades, and as they require not the intervention of mordants, the softness of the wool is preserved, and the process of dyeing becomes both cheap and simple.

354. Walnut peels are not gathered till the nuts are completely ripe, when they are put into large casks, along with as much water as is sufficient to cover them. When used in dyeing at the Gobelins in Paris, Berthollet informs us, they are kept for upwards of a year, and very extensively used; but if not made use of till the end of two years, they yield a greater quantity of colouring matter, at which time their odour has become peculiarly disagreeable and fetid. The peels separated from the nuts before they arrive at maturity, may likewise be used in dyeing, but in this state they do not keep so long.

355. Sumach (rhus coriaria, Linn.) is a shrub produced naturally in Palestine, Syria, Portugal, and Spain, being carefully cultivated in the two last of these countries. Its shoots are annually cut down, dried, and reduced to powder in a mill, by which process they are prepared for the purposes of dyeing.

356. The infusion of sumach, which is of a fawn colour with a greenish tinge, is changed into a brown by exposure to the air. A solution of potash has little action on the recent infusion of sumach; its colour is changed to yellow by the action of acids; the liquor becomes turbid by means of alum, a small quantity of precipitate being at the same time formed, and the supernatant liquor remaining yellow. A copious precipitate of a yellowish green colour is thrown down by sulphate of copper, and the liquor remains clear. No change is speedily produced by muriate of soda (common salt), but it becomes rather turbid at the end of some hours, and its colour is rather clearer. Sulphate of copper produces a copious precipitate of a yellowish green, which after standing some hours, changes to a brownish green; the supernatant liquor, which is slightly yellow, remains clear. Sulphate of zinc renders the liquor turbid, darkens its colour, and produces a deep blue precipitate; but when the sulphate of zinc is pure, the precipitate, which is of a brownish fawn colour, is in very small quantity. Acetate of lead gives a copious precipitate, of a yellowish colour; the supernatant liquor is of a clear yellow colour. No astringent has so strong a resemblance to galls as sumach; but the precipitate... DYEING

Of Simple precipitate thrown down from an infusion of it by a solution of iron, is not so copious as that which is yielded by an equal quantity of galls, on which account fumach may be generally employed as a substitute for galls, only its quantity will require to be increased.

357. The bark of the birch-tree (Betula alba, Lin.) yields a decoction of a clear fawn colour, but it soon becomes turbid and brown. The addition of a solution of alum in the open air, produces a copious yellow precipitate; a solution of tin gives also a copious precipitate of a clear yellow colour. With solutions of iron the decoction of the birch-tree strikes a black colour, and it dissolves in considerable quantity the oxide of iron, but in smaller proportion than the decoction of walnut peels. On account of this property it is employed in the preparation of black vats for dyeing thread.

358. Saunders, or fandal wood, is also employed for the purpose of giving a fawn colour. There are three kinds of fandal wood, the white, the yellow, and the red. The last only, which is a compact heavy wood, brought from the Coromandel coast, is used in dyeing. By exposure to the air it becomes of a brown colour; when employed in dyeing, it is reduced to fine powder, and it yields a fawn colour with a brownish shade, inclining to red. But the colouring matter which it yields of itself is in small quantity, and it is said that it gives hardness to woollen stuffs. When it is mixed with other substances, as fumach, walnut peels, or galls, the quantity of colouring matter is increased; it gives a more durable colour, and produces considerable modifications in the colouring matter with which it is mixed. Sandal wood yields its colouring matter to brandy, or diluted alcohol, more readily than to water.

359. Soot communicates to woollen stuffs a fawn or brown colour, of a lighter or deeper shade, in proportion to the quantity employed; but the colour is fading, and its affinity for wool is not great; and besides leaving a disagreeable smell, it renders the fibres harsh. In some manufactories, it is employed for browning certain colours, and it produces shades which could not otherwise be easily obtained.

II. Of the Processes for Dyeing Woollen, &c. a Fawn or Brown Colour.

360. In dyeing with walnut peels, a quantity proportioned to the quantity of stuff, and the intensity of shade wanted, is boiled for fifteen minutes in a copper. All that is necessary in dyeing with this substance is, to moisten the cloth or yarn with warm water, previous to their immersion in the copper, in which they are to be carefully stirred till they have acquired the proper shade. This is the process, if the aluminoous mordant is not employed. In dyeing cloth, it is usual to give the deepest shades first, and the lighter ones afterwards; but in dyeing woollen yarn, the light shades are given first, and the deeper ones afterwards. An additional quantity of peels is joined to each parcel.

361. Berthollet made a number of experiments to ascertain the difference of colour obtained from the simple decoction of walnut peels, and the addition of metallic oxides as mordants. The oxide of tin, he found, yielded a clearer and brighter fawn colour than that of the simple decoction. The oxide of zinc produced a still clearer colour, inclining to ash or gray. Compound colours from oxide of lead had an orange cast, while that from oxide of iron was of a greenish brown.

362. A fawn colour, which has a shade of green, is obtained from fumach alone; but to cotton stuffs dyeing which have been impregnated with printers mordant, with fumach communicates a good wash and durable yellow. Here, however, some precaution is necessary in the use of this substance for this purpose; for as the colouring matter is of so fixed a nature, the ground of the stuff cannot be bleached by exposure on the grats. This inconvenience is avoided by impregnating the whole of the stuff with different mordants, producing in this way a variety of colours, and leaving no part white.

363. Vogler employed the tincture of saunders wood with fandal for dyeing patterns of wool, silk, cotton, and linen, wood, having previously impregnated them with a solution of tin, and afterwards washing and drying them. Sometimes he used the solution unmixed, and at other times added fix or ten parts of water, and in whatever way he employed it, he obtained a poppy colour. When the mordant employed was solution of alum, the colour was a rich scarlet; with sulphate of copper it was a clear crimson, and with sulphate of iron a beautiful deep violet.

CHAP. II. Of Compound Colours.

364. A mixture of two colouring substances, it is Nature of well known, produces a very different shade from that compound of either of the uncombined colouring matters; hence colours, compound colours are obtained, which are merely mixtures of simple colours. It would undoubtedly be a desirable thing to ascertain with accuracy the peculiar shade produced by the combination of two colouring matters; but these results can only be certainly known by experiment, because by the action of different substances in the baths, they are subject to great variations in their effects, according to the affinities which are brought into action, and the new combinations which are formed. What is natural to colouring particles is not to be considered as a constituent part of compound colours, but only the difference of shade which they ought to assume, with a particular mordant, or in a particular bath. The effects, therefore, of the chemical agents employed in these processes, and the result of different combinations, ought to be particularly attended to. It is in dyeing compound colours that skill and ingenuity are most conspicuous, and their application of greatest utility, to enable the dyer to vary his processes, according to the shade desired, and at the same time to accomplish his operations by the shortest and cheapest means.

365. As compound colours are obtained by the mixture of simple colours, very different shades will be obtained from different proportions of the simple colours; hence compound colours exhibit an indefinite variety of shade, and the processes by which they are produced are very numerous. It would extend this treatise to an unusual length, were we to attempt to describe every variety of shade which is obtained from the mixture of simple colours. We shall therefore limit our observations to some of the principal compound colours, and an Compounds an account of the processes by which they are obtained, leaving it to our readers, who have made themselves familiar with the principles already detailed, to vary these colours, by employing different proportions and different combinations of simple colouring matters.

366. Compound colours have been usually divided into four classes, namely, green, purple, orange, and gray or drab colour. These are obtained from mixtures of the following simple colours.

1. Blue and yellow produce a green. 2. Red and blue, a purple, &c. 3. Red and yellow, orange. 4. Black and other colours, gray, &c.

The following sections will be occupied in a short detail of the methods which are usually employed in producing these different compound colours.

Sect. I. Of the Mixture of Blue and Yellow, or Green.

367. Green colours, from the great variety of shades which they exhibit, have been long known by different names, by which the intensity of shade is characterized, such as sea-green, apple-green, meadow or grass green, pea-green, parrot-green, &c. Many plants afford a green colour, such as brome grass (Bromus secalinus, Lin.), green berries of Rhamnus frangula, wild chervil (Cheerophyllum fylvetra, Lin.), purple clover (Trifolium pratense), common reed (Orinus phragmites). These colours, however, do not possess sufficient permanency. According to D'Ambourney, indeed, a permanent green may be obtained from the fermented juice of the berries of the berry-bearing alder (Rhamnus frangula). Having previously prepared the cloth with tartar, solution of nitrate of alum and common salt, he added to the fermented juice of the berries, after it was warmed, a small proportion of acetate of lead; and in this bath he communicated to the cloth an intermediate shade between parrot and grass green. But it is usually from the mixture of blue and yellow that green is obtained; and it may be observed, that it requires much skill and experience, especially in giving light shades, to produce a colour which is uniform, and entirely without spots.

I. Of the Processes for Dyeing Woollen Stuffs Green.

368. To dye woollen green, either the yellow or the blue dye may be given to it first. But when the stuff is first dyed yellow, and in this state is introduced into the blue vat, part of the yellow colouring matter being dissolved in the vat, communicates to it a green colour, which renders it unfit for dyeing any other colour than green. To avoid this inconvenience, therefore, the blue colour is first given, and afterwards the yellow. It would be quite unnecessary to resume the account of any part of the processes for dyeing blue, which have been already detailed. It is proper, however, to add, that the intensity of the blue shade must be proportioned to the green, or to the depth of the green colour which is wished to be obtained. Thus, for instance, to produce a parrot green, a ground of sky blue is given, and for the green like that of a drake's neck, a deep blue is required. When the blue dye has been communicated, the yellow is afterwards given, according to some of the processes which have been already described for dyeing yellow. The proper ground being communicated to the cloths, they are washed in the fulling mill, and boiled as for the common process of welding; but when the shade is light, the proportion of faults should be less. Cloths which are to receive light shades are first boiled, and when they are taken out, tartar and alum are added in fresh portions, till the cloths which are intended for the darkest shades are boiled. The process of welding is conducted in the same way as for dyeing yellow, with this difference, that a larger proportion of weld is employed, excepting for lighter shades, when the proportion must be smaller. In dyeing green, it is usual to have a succession of shades at the same time; the process is begun with the deepest, and ends with the lightest. Between each dip there should be an interval of one-half or three-quarters of an hour, and at each interval water is added to the bath. It is the practice of some dyers to give each parcel two dips, beginning the first time with the deep shades, and the second with the lighter ones; but when this practice is followed, the time of immersion should be shortened. In dyeing very light shades, the bath should never be permitted to reach the boiling temperature. For deep greens, a browning is given with logwood, and a small proportion of sulphate of iron.

369. For some kinds of green, sulphate of indigo is Saxon employed; and in this case either the blue and yellow green are dyed separately, or the whole of the ingredients are mixed together in the bath, and the whole process is finished at a single operation. The colour thus obtained has been distinguished by the name of Saxon green. The following is the process recommended by Dr Bancroft.

370. "The most beautiful Saxon greens (says he) may be produced very cheaply and expeditiously, by combining the lively yellow which results from quercitron bark, muriato-sulphate of tin, and alum, with the blue afforded by indigo when dissolved in sulphuric acid, as for dyeing the Saxon blue.

"To produce this combination most advantageously, the dyer, for a full-bodied green, should put into the dyeing vessel after the rate of six or eight pounds of powdered bark, in a bag, for every 100 lb. weight of cloth, with only a small proportion of water as soon as it begins to grow warm; and when it begins to boil, he should add about six pounds of muriato-sulphate of tin (with the usual precautions), and a few minutes after, about four pounds of alum; these having boiled together five or six minutes, cold water should be added, and the fire diminished so as to bring the heat of the liquor nearly down to what the hand is able to bear; and immediately after this, as much sulphate of indigo is to be added as will suffice to produce the shade of green intended to be dyed, taking care to mix it thoroughly with the first solution by stirring, &c.; and this being done, the cloth previously scoured and moistened, should be expeditiously put into the liquor, and turned very briskly through it for a quarter of an hour, in order that the colour may apply itself equally to every part, which it will certainly do in this way with proper care. By these means, very full, even, and beautiful greens may generally be dyed in half an hour; and during this space, it is best to keep the liquor at rather less than a boiling heat. Muriato-sulphate of Compound of tin is infinitely preferable, for this use, to the dyer's spirit; because the latter consists chiefly of nitric acid, which by its highly injurious action upon indigo, would render that part of the green colour very fugitive, as I have found by repeated trials. But no such effect can result from the muriatic acid of tin, since the muriatic acid has no action upon indigo; and the sulphuric acid is that very acid which alone is proper to dissolve it for this use.

Respecting the beauty of the colour thus produced, those who are acquainted with the unequalled lustre and brightness of the quercitron yellows, dyed with the tin balsam, must necessarily conclude, that the greens composed therewith will prove infinitely superior to any which can result from the dull muddy yellow of old fustic; and in point of expense, it is certain that the bark, muriatic acid of tin, and alum necessary to dye a given quantity of cloth in this way, will cost less than the much greater quantity (six or eight times more) of fustic, with the alum necessary for dyeing it in the common way, the sulphate of indigo being the same in both cases. But in dyeing with the bark, the vessel is only to be filled and heated once; and the cloth, without any previous preparation, may be completely dyed in half an hour; whilst in the common way of producing Saxon greens, the copper is to be twice filled; and to this must be joined the fuel and labour of an hour and a half's boiling and turning the cloth, in the course of preparation, besides nearly as much boiling in another vessel to extract the colour of the fustic; and after all the dyeing process remains to be performed, which will be equal in time and trouble to the whole of the process for producing a Saxon green with the bark; so that this colour obtained from bark will not only prove superior in beauty, but in cheapness, to that dyed as usual with old fustic.*

II. Of the Processes for Dyeing Silk Green.

371. In giving silk a green colour, greater precaution is necessary, to preserve uniformity of colour, and to prevent spots and stripes. Silk which is intended to receive a green colour, is scoured in the same way as for other colours; but for light shades, the scouring must be as complete as for blue. Silk which is to be dyed green, is first dyed yellow, and being well alummed, it is slightly washed at the river, and divided into small parcels, that it may receive the colouring matter uniformly, and then carefully turned in the weld bath. When the ground is supposed to have acquired a sufficient degree of intensity, a pattern is put into the blue vat, to ascertain the proper shade. When this is the case, the silk is taken out of the bath, washed, and immersed in the blue vat. To produce a deeper colour, and at the same time to give variety of shade, a decoction of logwood, fustic, or annatto, is added to the yellow bath, after the weld has been taken out. For very light shades, such as apple and sea green, it is scarcely necessary to add, that a weaker ground is to be given. For all light shades except sea green, the process is found to succeed better when the yellow is communicated by baths which have been already used; but these baths should not contain any logwood or fustic.

372. Saxon green is produced by means of sulphate of indigo. This is a brighter, but less durable colour than the former. This process is conducted by boiling as for welding, after which the cloth is washed. Fus- fusic in chips is enclosed in a bag, put into the same bath, and boiled for an hour and a half; when it is taken out, and the bath allowed to cool till the hand can bear it. A pound and a quarter of sulphate of indigo for each piece of cloth of eighteen yards, is added. The cloth is at first to be turned quickly, and afterwards more slowly, and it should be taken out before the bath boils. Some dyers put in only two-thirds of the solution at first; and after two or three turns, take out the cloth, and add the other one-third. By this means the colour is more uniform.

373. To produce Saxon green at one operation, the following process is recommended by Dr Bancroft. A ration bath is prepared of four pounds of quercitron bark, three pounds of alum, and two pounds of muriatic acid, with a sufficient quantity of water. The bath is boiled ten or fifteen minutes, and when the liquor is so far reduced in temperature as the hand can bear it, it is fit for dyeing. By adding different proportions of sulphate of indigo, various and beautiful shades of green may be obtained, and the colour thus produced is both cheap and uniform. Care should be taken to keep the bath constantly stirred, to prevent the colouring matter from subsiding. Those shades which are intended to incline most to the yellow, should be dyed first; and by adding sulphate of indigo, the green, having a shade of blue, may be obtained. This process, Dr Bancroft observes, is the most commodious and certain for dyeing the most beautiful Saxon greens upon silk†.

374. To produce English green, which is more beautiful than common green, and is said to be more durable than the Saxon green, Guhlke gives the following process. He first dyes the silk of a light-blue in the cold vat already described (316.), then soaks it in warm water, washes it in a stream, and dips it in a weak solution of alum. He then prepares a bath of sulphate of indigo, one ounce of solution of tin, with the tincture of French berries made with aceto-citric acid. The silk is kept in this bath till it has obtained the desired colour. It is then washed and dried in a shady place. Lighter shades may be dyed afterwards‡.

III. Of the Processes for Dyeing Cotton and Linen Green.

375. Cotton and linen, after being scoured in the usual way, are first dyed blue; and after being cleaned, given they are dipped in the weld bath, to produce a green colour. The strength of the blue and yellow is proportioned to the shade of green which is wanted. But as it is difficult to give to cotton velvet an uniform colour in the blue vat, it is first dyed yellow with turmeric, and the process is completed by giving it a green with sulphate of indigo. The same result, however, will be obtained by commencing the process either with the yellow or the blue.

376. The process which D'Apligny describes for dyeing cotton velvet, or cotton thread a sea or apple-cotton velvet green in one bath is the following. A quantity of verdigris is dissolved in vinegar, and the mixture is kept excluded from the air in the heat of a stove for fifteen days. A quantity of potash equal in weight to the verdigris employed is dissolved in water, and four hours... Compounds hours before dyeing it is added to the solution of verdigris. This mixture is to be kept hot. One ounce of alum in five quarts of water for each pound of stuff being prepared, the cotton thread or velvet is soaked in this solution. It is then taken out, and the verdigris mixture being added to the solution of alum, it is again introduced to be dyed.

377. The different shades of olive green, and drake's neck green, are given to thread after it has received a blue ground, by galling it, and dipping it in a weaker or stronger bath of iron liquor, then in the weld bath, to which verdigris has been added, and afterwards in the bath with sulphate of copper. The colour is lastly to be brightened with soap.

378. Cotton dyed with Prussian blue may be dyed green by previously aluming while it is still wet with the blue, and then dipping in a weld bath, the strength of which is proportioned to the shade required. The colour from weld is more lively than that obtained from fustic. But fustic which gives a deeper shade than weld, and diminishes the brightness of the blue, is to be preferred when a green with an olive shade is wanted.

379. The shade of green given to any stuff, it is obvious, must vary according to the intensity of the blue shade, the strength of the yellow bath, and the nature of the yellow colouring matter employed. Yellow colours are rendered more intense by means of alkalies, sulphate of lime and ammoniacal salts; but become fainter by means of acids, alum, and solutions of tin. In dyeing Saxon green the result will be different according to the process which is followed. The effects will be different by adding a yellow to a Saxon blue, from the process in which the sulphate of indigo is mixed with the yellow ingredients; because in the latter case the sulphuric acid has a considerable action on the colouring matter, and thus diminishes the intensity of the yellow. As the particles of indigo have a stronger affinity for the stuff than the yellow colouring matter, in dyeing a succession of shades in a bath in which both are mixed, the bath being first exhausted of the indigo, the last shades incline more to the yellow on account of the predominance of the yellow colouring matter.

Sect. II. Of the Mixture of Red and Blue, or Purple, &c.

380. By the mixture of red and blue, violet, purple, dove-colour, lilac, and a great variety of other shades, according to the proportions of the substances employed, or the predominance of the blue or the red, are produced. In stuffs which are to be dyed violet, a deeper blue must be given, but for purple colours, the ground requires to be of a lighter blue; but in lilac and similar light colours, it is necessary that both the blue and the red have a light shade.

I. Of Dyeing Wool Violet, Purple, &c.

381. In the attempts which have been made to communicate a violet or purple colour to a scarlet ground, according to the observations of Hellot, the colour is very unequal. It becomes therefore necessary to give the blue colour first; and for violets and purples, the shade of blue ought not to be deeper than that of sky blue. The stuff being dyed blue, is boiled with alum, and two fifths of tartar, and is afterwards dipped in a bath composed of nearly two thirds the quantity of cochineal required for scarlet, with the addition of tartar. The same process, indeed, as for dyeing scarlet, is followed. It is a common practice to dye these colours after the reddening for scarlet, making such additions of cochineal and tartar as the intensity of the shade may require.

382. For lighter shades, as lilacs, dove-colours, &c., the stuff may be dipped in the bath which has served for violet and purple, and is now somewhat exhausted, taking care to add a quantity of alum and tartar. For reddish shades, such as peach blossom, a small proportion of solution of tin is added. It may be observed, in general, that although the proportion of cochineal is less in dyeing lighter shades, the quantity of tartar must not be diminished.

383. To obtain the same colours, a shorter and less expensive process is recommended by Poerner. In this shorter process he employs sulphate of indigo. He boils the process stuff in a solution of alum, in the proportion of three ounces of the latter to one pound of the former, for an hour and a half, and afterwards allows it to remain in the liquid for a night after it has cooled. The dyeing bath is prepared with an ounce and a half of cochineal, and two ounces of tartar, which are boiled for three quarters of an hour: two ounces and a half of sulphate of indigo are then added, the whole is stirred, and boiled gently for fifteen minutes. The dyeing operation is conducted in the usual way, and a beautiful violet is thus obtained. To have all the variety of shades which are produced by the mixture of red and blue, the proportion of the sulphate of indigo is increased or diminished. It is sometimes increased to five ounces, and diminished to five drachms, for each pound of stuff. The quantity of cochineal is also varied, but when it is less than an ounce, the colour is dull. Different proportions of tartar are also employed. To produce variety of shades, the stuff is also prepared with different proportions of solution of tin.

384. To communicate a purple colour to wool, as Purple from well as some other shades, logwood, with the addition logwood of galls, has been employed. The stuff is previously dyed blue, and to give a brown shade, sulphate of iron is used; but the colours thus obtained are not permanent. By the following process, described by Decroizille, a durable dye is produced, by means of this wood. He dissolved tin in sulphuric acid, to which were added common salt, red acidulous tartarite of potash, and sulphate of copper; or it may be more conveniently done by making a solution of tin in a mixture of sulphuric acid, common salt, and water, to which are to be added the tartarite and sulphate in the state of powder. Of this mordant not less than 1500 quarts were made in twenty four hours, in a leaden vessel to which a moderate heat was applied. A very lucrative trade was carried on for three years by Decroizille, who sold it at the rate of 1s. 3d. sterling per pound.

385. If wool in the fleece is to be dyed, it will require a third of its weight of this mordant, while a fifth is a proportion sufficient for stuffs. A bath is prepared of such a degree of temperature as the hand can bear, with which the mordant is properly mixed, and the wool or stuff dipped in it and stirred, the same degree Compound of temperature being kept up for two hours, and increased a little towards the end; after which it is taken out, aired, and well washed. A fresh bath of pure water is prepared at the same temperature, to which is added a sufficient quantity of the decoction of logwood; the stuff is then immersed, stirred, and the heat increased to the boiling temperature, which is to be continued for 15 minutes, after which the stuff being taken out, aired, and carefully rinsed, the process of dyeing is completed. If for every three pounds of wool, one pound of a decoction of logwood has been used, and a proportionate quantity for stuffs which require less, a fine violet colour is produced, to which a sufficient quantity of brazil-wood imparts the shade known in France by the name of prune de Monfeur.

386. Logwood and brazil, fustic and yellow wood, are colouring substances which may be fixed with advantage upon wool by means of this mordant. The colour communicated by the two first of these is liable to be changed in the fulling by the action of the soap or urine employed for that purpose; but this change, which is always produced by alkaline substances, is remedied by a slightly acid bath a little hot, called brightening, for which the sulphuric acid has the preference. The colour becomes as deep, and frequently much brighter than before the change. Wools which have been dyed by means of this mordant, are said to admit of being spun into a finer and more beautiful thread, than by the use of alum. If the use of sulphate of copper is omitted, more beautiful colours are produced by fustic and yellow wood, as well as by weld. An orange red colour is communicated by madder, but not so deep as with a similar quantity of alum. When sulphate of copper is omitted, the wool is said to become much harsher, and the mordant thus prepared yields but indifferent colours with logwood, and in particular with brazil-wood. The use and carriage of this mordant are inconvenient, on account of the heavy sediment by which the vessel is half filled under a corrosive liquor, capable only of being kept in stone ware. These inconveniences may be remedied by the omission of the water in the receipt, which leaves only a part more conveniently used, and the carriage of it two-fifths cheaper.

387. The above process is thus explained by Berthollet. The decomposition of the muriate of soda is effected by the action of the sulphuric acid, and the muriatic acid being thus disengaged, dissolves the tin, part of which is precipitated by means of the tartaric acid, producing the sediment already mentioned. The oxide of copper produces the blue with the colouring particles of the logwood; the violet is formed by the oxide of tin with the same wood, and the red, with the colouring matter of the brazil-wood. The same ingenious chemist farther observes, that as an excess of acid is retained in the liquor, it might probably be of advantage to employ acetate as a substitute for sulphate of copper, in which case the action of the free acid would be moderated. He thinks it would still be more advisable to make use of verdigris; because the uncombined part of the oxide of copper would, in that case, unite with the excess of acid, on which account a smaller quantity of acid would remain in the liquor; and probably the quantity of tartar might be diminished, as a smaller quantity of tin would thus be precipitated.

II. Of Dyeing Silk Violet or Purple.

388. Silk is capable of receiving two kinds of violet colours, denominated the fine and the false, the latter of which is produced by means of archil or brazilwood. When the fine violet colour is required, the silk must first be paffed through cochineal, and dipped afterwards in the vat. The preparation and dyeing of the silk with cochineal are the same as for crimson, with the omission of tartar and solution of tin, by means of which the colour is heightened. The quantity of cochineal made use of is always proportioned to the required shade, whether it is more or less intense; but the usual proportion for a fine violet colour is two ounces of cochineal for each pound of silk. When the silk is dyed, it is washed at the river, twice beetleed, dipped in a vat more or less strong, in proportion to the depth of the violet shade, and then washed and dried with precautions similar to those which all colours require that are dyed in the vat. If the violet is to have greater strength and beauty, it is usual to pass it through the archil bath, a practice which, though frequently abused, is not to be dispensed with for light shades, which would otherwise be too dull.

389. When silk has been dyed with cochineal according to the above directions, only a very light shade is requisite for purple; the shades which are deepest are dipped in a weak vat, while dipping them in cold water is sufficient for such as are lighter, the water having been incorporated with a small quantity of the liquor of the vat, because in the vat itself, however weak it might be, they would acquire too deep a tinge of blue. In this manner are the light shades of this colour, such as gilly-flower, peach blossom, &c., produced by diminishing the quantity of cochineal.

390. There are various ways of imparting to silk whatever are denominated the false violets; but those let, which are most frequently used, and polished of greatest beauty, are prepared with archil, the bath of which is, in point of strength, to be suited to the colour required. Having been beetleed at the river after scouring, the silk is turned in the bath on the skein sticks; and when the colour is deemed sufficiently deep, a pattern is tried in the vat, to ascertain whether it takes the violet colour intended to be produced. If the shade is found to have acquired the proper depth, the silk is beetleed at the river and dipped in the vat, in the same way as for the fine violet colours; and let either of the blue or of the archil colour is given, according as it is meant that the red or blue shade of the violet colour should predominate.

391. The process recommended by Guhlche for communicating a violet colour to silk is the following. A pound of silk is to be soaked in a bath of two ounces of alum, and a like quantity of solution of tin, after having carefully poured off the sediment formed in the mixture. The dye-bath is prepared with two ounces of cochineal reduced to powder with a dram of tartar, and the remaining part of the bath which has answered the purpose of a mordant, with the addition of a sufficient quantity of water. When slightly boiled, such a quantity of solution of indigo is added as may communicate cate to the bath a proper shade of violet; after which the silk is immersed, and boiled till it has acquired the intended shade. It is then wrung, washed in a stream, and like every other delicate colour, must be dried in the shade. The light shades exhaust the bath. But it ought to be observed, that this colour, which is said to be a beautiful violet, possesses little durability, and is apt to assume a reddish tinge, owing to the colour of the indigo fading first.

392. A violet colour may be imparted to silks, by immersing them in water impregnated with verdigrise, as a substitute for aluming, and next giving them a bath of logwood, in which they assume a blue colour, which is converted to a violet, either by the addition of alum to the bath, or by dipping them in a weaker or stronger solution of that substance, which communicates a red colour to the particles of logwood. This violet possesses but a small degree of beauty, and little durability. But if alumed silk be immersed in a bath of brafil-wood, and next in a bath of archil, after washing it at the river, a colour is obtained possessing a much higher degree of beauty and intensity. The process described above (385.), for dyeing wool, succeeds equally well, according to M. Decroizille, in communicating to silk a violet colour.

III. Of Dyeing Cotton and Linen Violet.

393. The most ordinary mode by which a violet colour is communicated to cotton and linen stuffs, is first to give them a blue ground in the vat, proportioned to the required shade, and to dry them. They are afterwards galled, in the proportion of three ounces of galls to a pound of stuff, and being left in this bath for 12 or 15 hours, are wrung out and dried again. They are next passed through a decoction of logwood, and when thoroughly soaked and taken out, the bath receives an addition of two drams of alum, and one of dissolved verdigrise for each pound of cotton or thread. The skeins are then dipped again on the skein sticks, and turned for about 5 minutes, when they are taken out and aired. They are next immersed in the bath for 15 minutes, taken out and wrung. To complete the process, the vat employed is emptied; half of the decoction of logwood not formerly made use of is now poured in, with the addition of two drams of alum, and the thread is again dipped in it till it has acquired the shade proposed, which must always regulate the strength or weakness of the decoction of logwood. This colour resists in a considerable degree the action of the air, but in point of permanency is much inferior to that which is obtained from the use of madder.

Sect. III. Of the Mixture of Yellow and Red, or Orange.

394. Orange is the usual result of a composition of yellow and red colours, but an almost endless variety of shades may be produced, according as we vary the proportion of the ingredients, and the particular nature of the yellow used. It is sometimes the practice of dyers to combine blue with yellow and red, the result of which is the colour denominated olive. Many varieties may be obtained from the use of weld, saw-wort, dyers-weed, and other yellows, and by employing tartar, alum, sulphate of zinc, or sulphate of copper in the bath, or in the preparation of the Compound Colours.

I. Of Dyeing Wool Orange.

395. By a process exactly the same as that which is followed in communicating to stuffs a scarlet colour, an orange may be given to wool; but the quantity of red must be diminished, and that of the yellow increased. If wool is dyed a red colour by means of madder, and afterwards yellow with weld, the resulting compound is a cinnamon colour, and the most proper mordant in this case is a mixture of alum and tartar. The shades may be varied at pleasure by substituting other yellow dye stuffs instead of weld, and by varying the proportions as circumstances may require. Wool may receive a reddish yellow colour by passing it through a madder bath, after it has undergone the usual process for yellow, which has already been described. The strength of the madder bath is always to be proportioned to the shade required. Brafil-wood is sometimes employed with yellow substances, or mixed with cochineal and madder. Snuff, chestnut, mulk, and other shades are produced, by substituting walnut-tree root, walnut peels or sumach, for weld.

II. Of Dyeing Silk, Orange, &c.

396. Logwood, brafil-wood, and fustic, communicate to silk a maroon and cinnamon colour, together &c., with all the intermediate shades. The silk is scoured in the usual manner, alumed, and a bath is prepared, by mixing together decoctions of the three different woods mentioned above, made separately, varying the quantity of each according to the shade intended to be given; but the proportion of fustic should be greatest. The silk is turned in the bath on the skein sticks, and when it is taken out, if the colour be uniform, it is wrung and again dipped in a second bath of these three ingredients, according to the effect produced by the first, in order to obtain the shade required.

397. The blue vat is not made use of, when an olive colour is to be communicated to silk. After being alumed, it is dipped in a bath of weld, which is made very strong. To this is afterwards added the juice of logwood, with a small quantity of solution of alkali when the silk is dipped. This converts it into green, and gives the olive colour. It is dipped again in this bath till it has acquired the shade wanted.

398. To communicate to it the colour known by the name of rotten olive, fustic and logwood are added to the bath after welding, without any alkali. If the colour wanted is to incline more to a red, the addition of logwood alone is sufficient. A sort of reddish olive may likewise be obtained, by dyeing the silk in a fustic bath, to which a greater or lesser quantity has been added of sulphate of iron and logwood.

III. Of Dyeing Cotton and Linen Orange, &c.

399. A cinnamon colour is communicated to thread cinnamon and cotton, by commencing the process for dyeing colour, them with verdigrise and weld; they are afterwards to be dipped in a solution of sulphate of iron, denominated by the French bain d'affaiblissement, and then wrung out and dried. As soon as they are dried, they are galled in Compound the proportion of three ounces to the pound of stuff; then dried again, alumed as for red colours, and maddered. After being washed and dried, they are put into hot soap-flids, and turned till they have acquired a sufficient degree of brightness. It is the practice of some dyers to add to the aluming a decoction of fustic.

400. By boiling four parts of weld and one of potash in a sufficient quantity of water, M. d'Apligny informs us, a fine olive colour is communicated to cotton and thread. Brazil wood which has been steeped for a night, is boiled separately with a small quantity of verdigris, and these solutions are mixed together in various proportions, according to the particular shade required. The thread or cotton is dipped in the compound solution in the usual way.

Sect. IV. Of the Mixture of Black with other Colours.

The compound colours which are obtained from the mixture of black and other colours, are brown, gray, drab, &c., according to the nature and proportions of the simple colours employed.

I. Of Dyeing Woollen Stuffs Brown, Gray, &c.

401. To give a browning to cloth, as soon as it has been dyed, it is dipped in a solution of sulphate of iron, with the addition of an astringent, which makes a black bath. It is more common to mix a small quantity of solution of iron with a bath of water, adding more till the dyed stuff dipped in it has received the intended shade. Sulphate of iron is sometimes added to the dye bath; but by dipping the dyed stuff in a solution of this salt, the end is more easily attained. It is the usual practice of M. Poerner to soak the stuff in a solution of sulphate of iron, to which other ingredients are sometimes added, and after having taken it out of the mordant, it is dipped in the dye bath.

402. In order to obtain coffee and damascene colours, with other shades of browns of the common dye, the first method is adopted; a colour more or less deep is communicated to them, according to the shade intended to be obtained by the browning; and a bath is made of galls, fumach, and alder bark, with the addition of sulphate of iron. Those stuffs are first dipped to which the lightest shades are to be communicated, and when these are finished, the browner ones are dipped; a quantity of sulphate of iron being added for each operation, proportioned to the effect intended to be produced.

403. Blueish grays are communicated to stuffs, according to Poerner, by the solution of indigo in sulphuric acid, combined with a mixture of decoction of galls and sulphate of iron, varying the shades according to the different quantities of these ingredients made use of. If to a bath composed of cochineal, fustic and galls, sulphate of iron be added, other shades are obtained.

404. For marone, and such other colours as bear a strong resemblance to it, saunders and galls are employed, and sometimes a browning, with the addition of logwood. If dyed in the remains of a cochineal bath, these colours may be made to incline to a crimson or purple, and the same effect is produced by adding a small quantity of madder or cochineal to the bath. A little tartar gives a greater degree of bright compoundness to the colour. With a mixture of galls, fustic, and logwood, and a greater or smaller quantity of madder, with the addition of a little alum, those colours may be communicated to stuffs which are known by the name of hazel.

405. M. Guhliche produces what is called a puce co-puce colour, by boiling for fifteen minutes a pound of woollen stuff with two ounces of alum, a certain proportion of vinegar and solution of iron, after which he leaves it in the mordant for twelve hours. He then makes a bath with the decoction of two ounces of white galls carefully poured off from the sediment, and mixed with four ounces of madder, in which, when it grows hot, the stuff is immersed, after being taken out of the mordant, allowing it to remain there, while the temperature is gradually increased, till the colour intended has been imparted to it; after which it is boiled for two minutes, washed, and dried in the sun. The colour thus obtained possesses a great degree of durability. It is of a deeper brown by the omission of the alum and vinegar in the mordant; and after these colours the lighter shades are dyed. Sumach may be employed as a substitute for half of the madder. Different brown colours possessing considerable permanency, may likewise be produced by the use of brazil and logwood, if more or less of a solution of iron be mixed with a decoction of these substances. The wool being previously alumed and galled, is dyed in it.

II. Of Dyeing Silk with Mixtures of Black, &c.

406. M. Guhliche imparts to silk a purple violet purple without a blue ground, with a mixture of one part of galls dissolved in white wine, with three parts of water, in which a pound of silk is macerated for twelve hours, soaked in a mordant made up of two ounces of alum, one ounce of solution of tin, and half an ounce of muriatic acid. After wringing the stuff, it is dyed in a bath composed of two ounces of cochineal and a small quantity of solution of iron, till the intended shade has been communicated; and for shades which are lighter, the residue of these baths are sufficient, either separately or mixed together. Madder may be used in the same way, macerating a pound of silk in a solution of alum, mixed with an ounce of muriatic acid, and a quantity of solution of iron. When the stuff is wrung out, it is dyed in a bath made of eight ounces of madder. When deeper colours are wanted, some of the solution of galls in white wine is mixed with the madder and cochineal baths.

407. Silk may be dyed in a bath made of equal parts of brazil and logwood juice, adding a certain quantity of solution of iron, after the stuff has been soaked in a solution of two ounces of alum, and an ounce of muriatic acid. If solution of galls be added, the colour becomes deeper.

Colours resembling that of brick, may be produced, by immersing silk in an annatta bath, after preparing it with a solution of galls mixed with a certain quantity of solution of iron. By the mixture of brazil, logwood, archil, and galls, and by a browning with sulphate of iron, a number of different shades are produced; but the whole of them have more or less III. Of Dyeing Silk with Mixtures of Black, &c.

408. A permanent violet colour may be given to thread and cotton, when scoured in the ordinary way, by preparing a mordant with two quarts of the bath of what is called the black caulk, and four quarts of water for each pound of stuff, which is made to boil, and the scum is removed which forms on the surface, till it wholly disappears. The liquor is poured into a vat, and when warm, four ounces of sulphate of copper and one ounce of nitre are dissolved in it. The skeins are left to soak in it for ten or twelve hours, wrung out, and dried. If it is required to produce a deep violet colour, two ounces of verdigris must be added to the bath; and if the nitre be omitted, the colour becomes still deeper by galling the thread more or less, prior to its being put into the mordant. If the nitre be increased, and the sulphate of copper diminished, the violet colour becomes more inclined to lilac. A number of various shades may be produced, by different modifications of the mordants employed.

409. Cotton is galled, dipped, and wrought in the common way, when different shades of maroon colour are wanted. To the bath employed must be added more or less of the liquor of the black caulk. The cotton is then washed in a bath mixed with verdigris, next welded, and dyed to a fulvic bath, to which a solution of soda and alum is sometimes added. When the cotton prepared in this manner has been thoroughly washed, it is next well maddered, dipped in a weak solution of sulphate of copper, and last of all in soap suds.

410. For some hazel and snuff colours, a browning is communicated to stuffs by means of root, after the welding and madder bath, to which galls and fulvic have been added; sometimes root is mixed with this bath, and a browning is likewise imparted by means of a solution of sulphate of iron; and for browning colours, walnut peels are sometimes employed as a substitute for solutions of iron. For such wools as are designed for the manufacture of tapestry, they are very advantageous, because the colour is not changed into yellow by exposure to the air, as is the case in browning which is imparted by means of iron; but remains a considerable time without any sensible change. The hue is indeed rather dull; but its goodliness and very moderate price are sufficient to recommend a more extensive use of it for grave colours, which in common stuffs are sometimes fashionable.

CHAP. III. Of Calico-printing.

411. This may be defined to be the art of communicating different colours to particular spots on the surface of cotton or linen cloth, while the rest of the stuff retains its original white colour.

The wonderful and truly ingenious art of calico-printing seems to have been first known in India, and for more than two centuries before the commencement of the Christian era. Although the Egyptians were well acquainted with this art in the days of Pliny, as he himself informs us, it can scarcely be doubted that they derived the knowledge of it from India, as that country rather than Egypt, produced the colouring and other materials for carrying it on. If we consider its present improved state, the elegance of different patterns, the beauty and durability of the colours which can now be imparted to cotton or linen stuffs, and the dispatch with which the various operations of this art are conducted, we must be astonished at the rapidity of its improvements, when we recollect that it has been known in Europe for little more than a century. Perhaps no other art has risen to such perfection in so short a period.

412. Our readers will not expect that our account of this subject should be tedious or elaborate, since the art is presumed to be already acquainted with the different processes which are employed in calico-printing; and to such as with only for a general knowledge of the art, in a theoretical point of view, prolixity would be disagreeable.

413. The art of calico-printing consists in impregnating Nature of with a mordant, such parts of cotton or linen stuffs as this art are to have particular colours communicated to them, and then dyeing them in the usual manner with some colouring substance. Those parts of the cloth only which receive the mordant are intimately united with the colouring matter, although the whole surface must be more or less tinged; but the parts which have not received the mordant are restored to their original brightness by means of washing, and afterwards bleaching it upon the grats for some days, taking care to turn the wrong side towards the sun. If red stripes are to be communicated to a piece of white cotton cloth, those parts of its surface on which the stripes are intended to appear, are marked out by a pencil dipped in acetate of alumina; after which it is dyed with madder in the usual way. When it is first taken out of the dyeing vessel, its whole surface is red, but when it is washed and bleached, it resumes its original whiteness, the stripes only excepted which, being impregnated with the acetate of alumina, remain red. By a similar process may yellow or any other stripes be fixed upon cotton or linen, by the substitution of quercitron bark, weld, &c., in the room of madder.

414. When different parts of the cloth are to receive different coloured stripes at the same time, different morinate dyes must be employed. If stripes are delineated on different colours with the acetates of alumina and iron, and if it be then dyed with madder in the ordinary way, it will, after being washed and bleached as formerly directed, exhibit stripes of a red and brown colour. If the same mordants are employed, but quercitron bark used instead of madder, the stripes will then be yellow, and olive or drab.

415. The mordants known by the names of acetate of alumina and acetate of iron, which are made use of in calico-printing, may either be applied to stuffs with a pencil, as already mentioned, or still more expeditiously by means of blocks, on which the intended patterns are cut. Being designed only for particular parts of the surface of the cloth, great caution is necessary to prevent them from spreading to any part of it which is to remain white, and to prevent their interference when the application of more than one is required. Such a degree of confidence must of consequence be given to the mordants employed, as will prevent this disagreeable effect, which cannot fail to destroy the beauty and... and elegance of the print. If blocks are to be made use of, the mordants may be brought to a proper consistence by means of tarich; but gum arabic must be mixed with them, when the pencil is to be employed. The thickness should not exceed what is absolutely necessary to prevent the mordants from spreading; because, if carried too far, the cotton is frequently not saturated with the mordant, in consequence of which the dye is but imperfectly communicated.

416. To distinguish those parts of the cloth which are impregnated with mordants, it is a common practice to give the mordants some particular tinge by which they may be known; and for this purpose printers commonly make use of the decoction of brasil wood. Dr Bancroft objects to this practice, because he is of opinion that the process of dyeing is impeded by the colouring matter of brasil wood. The affinity of the dye stuff for the mordant displaces the colouring matter of the brasil wood; and without such affinity it would be impossible to strike the colour. Some of the dye-stuff to be employed afterwards is recommended by Dr Bancroft for colouring the mordant, who prohibits the use of a larger quantity than what is sufficient to render it indistinguishable when an application of it is made to the cloth. Should too large a quantity be united with the mordant, a considerable proportion of the latter would be combined with colouring matter, by which means its affinity for the cloth would be diminished, and therefore a permanent colour could not be expected to result from such a partial combination.

417. It is necessary to dry the cloth completely after the application of the mordants, for which purpose artificial heat may be employed, which has a tendency to promote the separation of the acetous acid from its base, and assist its evaporation, and thus the combination of the mordant with the cloth will be facilitated.

418. When the cloth is thoroughly dried, it is customary to wash it with warm water and cow-dung, till every particle of the starch or gum arabic which had been employed to give a proper consistence to the mordants, and those parts of them which do not combine with the cloth, are entirely removed. The loose particles of the mordant are entangled by means of the cow-dung, and prevented from being attached to those parts of the cloth which are to remain white. After this, it must be completely rinsed in pure water.

Colouring matters employed.

419. Indigo, madder, quercitron bark, and weld, are the chief dying ingredients made use of by calico-printers; but the last of these is seldom used by the printers of this country, except for the purpose of communicating yellows of a delicate greenish shade. Quercitron bark, on account of its inferior price, and capacity of imparting colours equally good, as well as requiring a less degree of heat, is employed as a substitute. It is usual to apply indigo at once, either by means of the block or pencil, because it requires not the intervention of a mordant to fix it. This preparation is made by boiling together indigo, potash reduced to the caustic state by means of quicklime, and orpiment; afterwards thickening the solution with gum. Dr Bancroft recommends the use of coarse brown sugar as a substitute for orpiment, which operates as powerfully in the decomposition of the indigo, and in promoting its solubility, answering at the same time all the purposes of gum.

420. When the cloth is thoroughly cleaned after it has been impregnated with the mordant, the dyeing process is conducted in the usual manner. As the whole of it receives a tinge of the dye, it must be completely washed and bleached for some days on the grats, as formerly mentioned, by which means the colour is entirely removed from those parts of the cotton not impregnated with the mordant, while all the other parts of it retain the colouring matter as powerfully as at first.

421. One of the most common colours imparted to Nankeen cotton prints is a species of nankeen yellow of different shades, and for the most part in stripes or spots. It is produced by means of a block on which is cut the intended pattern, rubbed over with acetate of iron brought to a proper consistence with gum or starch, and applied to the cotton; which, being dried and cleansed in the ordinary way, is immersed in a ley of potash. It is proper to observe, that the quantity of acetate of iron must be proportioned to the particular shade required.

422. In order to produce a yellow colour, the block is yellow, rubbed over with acetate of alumina; and the cloth, after being impregnated with this mordant, is dyed with quercitron bark in the common manner, and then bleached.

423. If madder be substituted for the quercitron bark, Red, a red colour is given to cotton by the same process.

424. To communicate to fluffs the fine light blue colours Blue, which we frequently behold upon cotton, the block is rubbed over with a composition consisting partly of wax, by means of which all those parts of its surface are to remain white. It is next dyed in a cold vat of indigo, and when it is dried, the wax composition may be removed by the use of hot water.

425. Lilac and blackish brown colours are communicated by acetate of iron, proportioning the quantity to the particular shade required, and adding a little fumach for such shades as are to be very deep. The cotton is then dyed with madder and bleached in the usual manner. Dove colour and drab are produced by means of acetate of iron and quercitron bark.

426. When a variety of different colours are to be made on the same print, a greater number of operations is necessary. Upon each of the blocks is cut that particular part of the pattern which is to have one appropriate colour; and when these blocks are rubbed over with their respective mordants and thus applied to the cloth, the dyeing process is afterwards conducted in the ordinary manner. If, for example, three different blocks are to be made use of, the first rubbed over with acetate of alumina brought to a proper consistence, the second with acetate of iron, and the third with a composition of these two, the colours resulting, after the dyeing and bleaching processes are finished, will be the following.

- Acetate of alumina yellow, - Iron olive, drab, dove. - From the compound olive green, olive.

It is proper to observe, that these are the results when quercitron bark is employed; but by the substitution of madder the following colours will be obtained.

Acetate Acetate of alumina red, iron brown, black.

From the compound purple.

When it is required to produce at the same time both those colours which are imparted by madder, and likewise by the use of quercitron bark, mordants are first applied for one part of the pattern, after which the cotton is dyed in a bath of madder, and then bleached. The rest of the mordants are then applied in a similar manner, after which the cotton is dyed with the quercitron bark, and bleached as before. The colours which the madder communicates are very little affected by the second dyeing, because the mordants by which their permanency is secured, are previously saturated. A new mordant may be applied to some of the colours resulting from the use of madder, by which means they receive a new durable colour from the bark. And by means of the indigo liquor other new colours may still be communicated after the last bleaching.

427. The following colours may be communicated to cotton, by means of the different processes which have been described.

Madder Dye.

| Acetate of alumina | red, | |-------------------|-----| | iron | brown, black, lilac, purple |

Bark Dye.

| Acetate of alumina | yellow, | |-------------------|--------| | iron | dove, drab, olive, orange |

Indigo Dye.

| Indigo | blue, | |------------------|-------| | Indigo and yellow | green |

Thus may twelve different colours be communicated to the same print by these different processes.

428. If durable colours could be directly applied to cotton by means of the block or pencil, without the help of mordants, nothing could be conceived more simple than the art of calico-printing; but with the single exception of indigo, the communicating of permanent colours requires the process of dyeing. Yellow, indeed, which is a compound colour, and some others, may be communicated to cotton at once, by mixing together an infusion of quercitron bark and acetate of alumina, while the same mordant with a decoction of madder, imparts to it a red colour; but those which are produced in this way are far from being durable, since they are destroyed by washing, and sometimes even by exposure to the air.

429. But as it is not always practicable for calico-printers to avoid the application of colours in this manner, every endeavour to give them a greater degree of permanency becomes an object of importance. The following composition has been recommended for a yellow printing colour. Three pounds of alum, and three ounces of pure chalk are to be dissolved in a gallon of hot water, to which are to be added two pounds of acetate of lead. This mixture is to be occasionally stirred for 24 or 36 hours, after which it is to remain at rest during 12 hours. The clear liquor is then to be poured off, and as much more hot water added to the residuum, as will, after being stirred and allowed to settle, amount to three quarts when added to the first quantity. Into a tinned copper vessel put five pounds, or at most a quantity not exceeding eight pounds, of quercitron bark sufficiently ground, and boil it for an hour in four or five gallons of clean soft water, adding afterwards a little more water if the bark is not properly covered. When the liquor is thoroughly boiled, let it be removed from the fire, and left to settle for half an hour, when the clear decoction is to be poured off through a fine sieve. Six quarts more of pure water are then to be put upon the same bark, and boiled for a quarter of an hour, being previously well stirred. When it has stood a sufficient time to settle, the clear liquor is to be strained off, and being mixed with the former, both are put into a shallow wide vessel to be evaporated by boiling, till the whole, in addition to the mordant already mentioned, and the gum or paste for bringing it to a proper consistence, does not exceed three gallons. It will be proper not to add the three quarts of aluminous mordant till the decoction has been cooled down almost to the natural heat of blood. Let gum arabic or gum fenegal be taken for thickening, if the pencil is to be used, and starch or flour when blocks are to be employed.

430. If a pound of muriatic sulphate of tin be used as for bright a substitute for the aluminous mordant in the composition described above, a mixture will be produced which is capable of imparting to cotton a very bright yellow, and considerably permanent.

431. A cinnamon colour possessed also of a sufficient degree of permanency may be given to cotton, by means of a mixture of sulphate of tin and a decoction of the quercitron bark.

432. If the decoctions of this bark and of logwood Green are boiled together, and proper quantities of sulphate of copper and verdigris added to them, together with a small proportion of carbonate of potash, there results a compound which communicates to cotton a green colour. Although the expectations of Dr Bancroft were not fully answered by the trials which he made of this substance, he deemed his success sufficient to encourage him to a farther investigation of it.

433. A permanent drab colour may be given to cotton by means of acetate of iron mixed with a decoction of quercitron bark, and reduced to a proper consistence. This mixture will also produce an olive, if added to the olive colouring liquor already mentioned; and the colours may be made still more permanent, if a solution of iron in diluted nitric or muriatic acid be used as a substitute for iron liquor. They ought, however, to be used sparingly and with caution, that the texture of the cotton or linen to which they are applied may not be injured.

434. Dr Bancroft made a number of experiments with the decoction of quercitron bark, to ascertain its effects when combined with different metallic salts as mordants. The sulphate, nitrate, and muriate of zinc, the quercitron decoction, yielded brownish yellow colours of different shades; but none of them were found sufficiently permanent when they were applied topically to linen or cotton. Mercury in the different acids produced

Indian Method of Dyeing Red.

duced with the decoction of bark different shades of brown or yellowish brown colours; but they did not prove more durable than the former. The nitro-muriate of platinum with a proper proportion of decoction of quercitron bark, afforded, when topically applied to linen or cotton, strong full-bodied fluff colours, which were found sufficiently permanent, and capable of resisting the action of acids, and of the sun and air. Nitrate of silver with a decoction of the bark, when applied topically to linen or cotton, produced strong dark brown and cinnamon colours of considerable durability. Nitrate of lead with the same decoction gave by topical application a drab colour which was not less durable than the former. Nitrate of bismuth produced with the decoction of bark a very full and strong brownish yellow. This colour, however, is attended with the inconvenience of becoming almost black when exposed to the action of the alkaline sulphurates, sulphurated hydrogen gas, or even by the action of common soap. Muriate of bismuth with the decoction gives a drab colour; sulphate of the same metal affords a yellow; but these colours when applied to cotton or linen are not durable. Nitro-muriate of antimony produced with the decoction of bark something of a fluff colour, which applied to linen and cotton possesses some degree of durability. Nitrate and muriate of cobalt with the quercitron bark gave different shades of brown; but these colours were extremely fugitive; they soon faded by exposure to the sun and air.

435. The art of calico-printing has been hitherto almost solely limited to linens and cottons. Many colouring matters have such an affinity for these stuffs that they readily enter into combination with them at the ordinary temperature of the atmosphere. This is also the case with silk, so that colouring matters might be applied topically to the latter by means of similar operations as to linen and cotton. Attempts, however, woollen have been made to extend the process of topical dyeing stuffs printing to woollen stuffs, and particularly those kinds known by the name of kerfeymeres, which are employed after being prepared in this way for waistcoat patterns. When it is recollected that woollen stuffs when they are to be dyed generally must be exposed to a considerable degree of heat, it is easy to conceive that it will be difficult to communicate spots or figures by printing to woollen stuffs. The means by which this difficulty is obviated in those manufactures where this operation is conducted have been hitherto kept secret. The preparation of colouring matters, whether such as may be employed simply or require the use of mortants to fix them, will be easily understood from what we have already fully detailed in the course of this treatise. The application of the colours is made in the usual way; and it is said that, after the woollen stuffs are printed, they are wrapped up in two or three folds of thick paper, to prevent the access of moisture which might cause the colours to run, and exposed to the steam of boiling water for such a length of time as may be supposed necessary for the colouring matter to combine with the stuffs.

APPENDIX.

After that part of the preceding treatise to which it properly belongs, was printed off, the following account of the Indian method of dyeing cotton cloth and cotton thread a red colour came under our notice. It was communicated to the society for the encouragement of arts, &c., by Mr Maclellan of Calcutta. The insertion of it may perhaps excite the curiosity of some of our countrymen to farther inquiries into the state of this as well as of other arts in India, where, from being long known and practised, many of them have arrived at a high degree of simplicity and perfection.

Directions for dyeing a bright Red, four yards of three-fourths broad Cotton Cloth.

1st. The cloth is to be well washed and dried, for the purpose of clearing it of lime and congee, or starch, generally used in India for bleaching and dressing cloths; then put into an earthen vessel, containing twelve ounces of chaya or red dye root, with a gallon of water, and allow it to boil a short time over the fire.

2d. The cloth being taken out, washed in clean water, and dried in the sun, is again put into a pot with one ounce of myrobalans, or galls coarsely powdered, and a gallon of clear water, and allowed to boil to one half; when cool, add to the mixture a quarter of a pint of buffalo's milk. The cloth being fully soaked in this, take it out, and dry it in the sun.

3d. Wash the cloth again in clear cold water, and dry it in the sun; then immerse it into a gallon of water, a quarter of a pint of buffalo's milk, and a quarter of an ounce of the powdered galls. Soak well in this mixture, and dry in the sun. The cloth, at this stage of the process, feeling rough and hard, is to be rolled up and and beetle till it becomes soft.

4th. Infuse into five quarts of cold water, six ounces of red wood shavings, and allow it to remain so two days. On the third day boil it down to two-thirds the quantity, when the liquor will appear of a good bright red colour. To every quart of this, before it cools, add a quarter of an ounce of powdered alum; soak in it your cloth twice over, drying it between each time in the shade.

5th. After three days wash in clean water, and half dry in the sun; then immerse the cloth into five gallons of water, at about the temperature of 120° of Fahrenheit, adding 50 ounces of powdered chaya, and allowing the whole to boil for three hours; take the pot off the fire, but let the cloth remain in it until the liquor is perfectly cool; then wring it gently, and hang it up in the sun to dry.

6th. Mix intimately together, by hand, about a pint measure of fresh sheep's dung, with a gallon of cold water, in which soak the cloth thoroughly, and immediately take it out, and dry it in the sun.

7th. Wash the cloth well in clean water, and spread it out in the sun on a sand-bank (which in India is universally preferred to a grass-plot) for six hours, sprinkling Directions for dyeing of a beautiful red, eight ounces of Cotton Thread.

1st. Put one gallon and a half, by measure, of sapwood ashes into an earthen pot, with three gallons of water, and allow the mixture to remain twenty-four hours to perfect it for use.

2nd. Put the following articles into an earthen pot, viz. Three quarters of a pint of Gingelly oil; one pint, by measure, of sheep's dung, intimately mixed by hand in water; two pints of the above ley.—After mixing these ingredients well, pour the mixture gradually upon the thread into another vessel, wetting it only as the thread, by being squeezed and rolled about by the hand, imbibes it, continuing to do so until the whole is completely soaked up, and allow the thread to remain in this state until next day.

3rd. Take it up, and put it in the sun to dry; then take a pint and a half of ash-ley, in which squeeze and roll the thread well, and allow it to remain till next day.

4th. Squeeze and roll it in a like quantity of ash-ley, and put it in the sun to dry; when dry, squeeze and roll it again in the ley, and allow it to remain till next day.

5th. Let the same process be repeated three or four times, and intermit till next day.

6th. Lay the thread once, as the day before, and, when well dried in the sun, prepare the following liquor: One gill of Gingelly oil; one pint and a half of ash-ley.—In this squeeze and roll the thread well, and leave it so till next day.

7th. Repeat the process of yesterday, and dry the thread in the sun.

8th. The same process to be repeated.

9th. First repeat the ash-ley process three or four times, as under the operations 3, 4, and 5, and then prepare the following mixture: One pint of sheep-dung water; one gill of Gingelly oil; one pint and a half of ash-ley.—In this squeeze and roll the thread well, and dry it in the sun.

10th. Repeat the same process.

11th. Do. Do.

12th. Do. Do.

13th. Do. Do.

14th. Do. Do.

15th. Wash the thread in clean water, and squeeze and roll it in a cloth until almost dry; then put it into a vessel containing a gill of powdered chaya root, one pint by measure of calhan leaves, and ten pints of clear water; in this liquor squeeze and roll it about well, and allow it to remain so till next day.

16th. Wring the thread, and dry it in the sun, and repeat again the whole of the 15th process, leaving the thread to sleep.

17th. Wring it well, dry it in the sun, and repeat the same process as the day before.

18th. Do. Do.

19th. Do. Do.

20th. Wring and dry it in the sun, and with the like quantity of chaya root in ten pints of water; boil the thread for three hours, and allow it to remain in the infusion until cold.

21st. Wash the thread well in clear water, dry it in the sun, and the whole process is completed.

INDEX.

Alum, a mordant for cotton, No 221 how applied, 222 Anota, history of, 248 properties of, 247 Apparatus for dyeing silk, 133 wringing out, 136 raking, 137 giving a ground, 138 dipping, 139 Archil, history of, 171 properties, 172 singular change of, 173 Arts, origin of, 2 when lost, 16 revived in Italy, 17 African, process for dyeing cotton red at, 223 mordant used at, 224 madder dye, how prepared at, 227

B. Bancroft, Dr., his process for dyeing scarlet, 200 advantages of it, 202 for blue, 314 prussian blue, 323 Batb, preparation of, for dyeing wool yellow, 255 cotton and linen, 277 Berthollet's experiments for trying the permanency of colours, 61 Betula alba, bark of, for dyeing brown, 357 Birch, bark of, used in dyeing brown, ib. Black, the substances used for dyeing, 326 process employed for, 330 Hellot's process for, ib. common process for, 331 cheaper process for, 332 process of the English dyers for, 333 Blue, how to dye wool, 292 accidents which may happen in the dyeing of, 293 how communicated in calico-printing, 424 Bodies, affinity of, for certain rays the cause of colour, 41 Bodier, white, effect of colours on, No 49 coloured, are compounds, 53 Boilers, what kind of, best for dyeing, 192 Brazil wood, history of, 178 properties, 179 Brown, substances used in the dyeing of, 351 properties of, 352 advantages, 353 C. Caldrons for dyeing, 132 Calico-printing, history of, 411 nature of, 413 different colours how communicated, 414 mordants used, 415 application of, 416 cloth washed, 418 and dried, 417 Candle light, effects of, on scarlets differently dyed, 203 Carthamus, history of, 174 preparation of, 175 Carthamus,

Carthamus, properties of, 176 Chamomile, use of, in dyeing, 251 Chemistry, importance of, in dyeing, 150 Cherry-red, how obtained, 215 Cochineal, history of, 160 varieties of, 162 attempts to cultivate, 164 properties of, 165 Colours, nature of, 29 division of, 151 simple, 152 caule of, explained, 30 durable, 267 Newton's theory of, 33 objections to, 36 supported, 34 inconsistent with facts, 37 of metals independent of density, 39 changes of, 42 from new combinations, 43 change of, produced by oxygen, 54 compound, explanation of, 364 how to try the permanency of, 56 green, 376 violet, 393 olive green, 377 for pencilling, 429 Cotton, origin of, 117 structure of, 118 affinity of, for colouring matter, 119 preparations for dyeing, 120 aluming, 121 galling, 122 process for dyeing madder or Turkey red, 217 at Afracan, 223 the Grecian method, 231 by Papillon at Glafgow, 238 by Haufman, 239 scarlet with cochineal, 241 crimson, 242 low dyed blue, 304 black, 346 green, 376 olive green, 377 violet, 393 Crimson, how dyed by one process, 208 by the conversion of scarlet, 209

D. Dove-colour, dyeing wool, 382 Drab-colour imparted to cloth by acetate of iron, 426 Dufay's experiments for trying the permanency of colours, 57 Dyeing, definition of, 1 origin of, 3

Index.

Indigo, different qualities of, from what obtained, 287 properties of, 289 used in two states, 290 Ingredients, proportion of, for reddening scarlet, 189 Iron, oxide of, as a mordant, 95 solution of, for the same, 74 how prepared, 349

K. Kermes, history of, 167 properties of, 168 Kuster brings the oxide of tin to London, 88

L. Lac, history of, 169 properties of, 170 Light, nature of, 28 Lilac, how communicated to cloth in calico-printing, 425 Lime, use of, in dyeing, precautions in the use of, 296 Linen, dyed yellow with weld, 273 blue, 304 black, 346 process followed at Manchestter for, 348 how dyed violet, 393 cinnamon colour, 399 olive, 400 dyed red with madder, 217 Liquor, purple, formed in snails, 15 Logwood, history of, 183 properties of, ib.

M. Madder, preparation of, 156, 184 process for dyeing with, 182 roofing, 183 properties of, 159 Marrone colour, how produced, 409 Matters, coloured, do not reflect light, 44 proof of this, 45 animal, used as mordants, 97 animal and vegetable, 103 coloured black by incident light, 47 Metallic oxides, use of, in dyeing, 84 Mordants, definition of, 66 importance of, 67 how applied, 69 effects of, explained, 70 various ways applied, 100 for dyeing cotton red, 218 used in dyeing black, 329 Mushrooms, use of in dyeing, 272

N. Nankeen, colour how to dye, 279 another process for, 280 how done in the east, 281 how communicated in calico-printing, 421

O. Index.

O. Olive, communicated to cloth in calico-printing by acetate of iron, No 426 and by the acetates of alumina and iron combined, ib. Orange colour, how produced, a compound of red and yellow, 366 various shades of 394

P. Papillon Mr., his process for dyeing red, 238 Penciling, colours for, 429 Platiere, De la, his method of dyeing with Prussian blue, 322 Poppy-red, how obtained, 214 Process for dyeing wool yellow, 258 Prussian blue, how to dye with, 320 Purple, Tyrian, celebrated by the ancients, a compound of red and yellow, 366 liquor, preparation of, 9 stuffs how prepared to receive, ib. permanency of, 10 high price of, 11 worn by the Romans, 12 still used in dyeing, 13 found in snails, 15

Q. Quercitron bark, history of, 248 properties, for dyeing wool yellow, 257

R. Red substances for dyeing, 155—180 how to obtain different shades of, 195 madder, for cotton, 217 Grecian method of obtaining, 231 how improved in the Levant, 237 how communicated in calico-printing, 423 Rose-colour, how obtained, 216 Rouge, preparation of, 177 madder, for wool, 182 silk, cotton and linen, 217 scarlet, crimson, 208

S. Salt, common, use of in dyeing scarlet, 196 Sandal wood, use of, in dyeing, 358 Saxon blue, discovery of, 313 how to dye with, 314 green, process for dyeing wool, 369

Saxon green, process for dyeing silk, No 372 Scarlet, process for dyeing, 187 with cochineal, 197 process for boiling, reddening, 188 how to give a bright red to, 191 a compound colour, 198 different shades of, 207 Shell-fish, producing a purple liquid, found on the French coast, method of catching, 14 Silk, how produced, scoured, treated when used white, to extract the colouring matter of, alumed, process for dyeing red, with madder, brazil wood, cochineal, weld, how prepared for a blue colour, Turkey blue, black, how galled, softened, raw, how to dye, how dyed green, purple, a process for dyeing, how dyed olive, purple-violet, brick colour, how dyed with the black cajf, Soot, use of, in dyeing, Stuff to be dyed should be white, Sumach, properties of, use of, in dyeing,

Vats recommended by Hauffman, No 310 Velvet, how dyed black, substances used instead of galls for, Verdigris, use of, instead of tartar in dyeing, 265

W. Walnut-peels, for dyeing brown, properties of, preparation of, Water, importance of, in dyeing, different kinds how distilling, method of purifying, tests for, Weld, use of, in dyeing yellow, properties of, Willows, sweet, leaves of, used in dyeing, Wood, use of, in dyeing blue, Wool, different modes of dyeing, structure of felted of, how fulled, importance of, dyed red with madder, process for dyeing, scarlet, crimson, yellow, blue, brown, black, green, purple, lilac, orange, coffee-colour, gray, puce colour, dyed purple with logwood, process for obtaining, Woollen stuffs, printing,

Y. Yellow, substances employed for dyeing, mordants necessary for a permanent, with an orange shade, bright golden, greenish, pale green, process for a cheap, how communicated in calico-printing, produced by acetate of alumina, composition for, in calico-printing, bright,