a clear limpid fluid, capable of hardening without losing its transparency, used by painters, gilders, &c. to give a lustre to their works, to preserve them and defend them from the air.
A coat of varnish ought to possess the following properties: 1. It must exclude the action of the air; because wood and metals are varnished to defend them from decay and rust. 2. It must resist water; for otherwise the effect of the varnish could not be permanent. 3. It ought not to alter such colours as are intended to be preserved by this means. It is necessary therefore that a varnish should be easily extended or spread over the surface, without leaving pores or cavities; that it should not crack or scale; and that it should resist water. Now resins are the only bodies that possess these properties. Resins consequently must be used as the bases of varnish. The question which of course presents itself must then be, how to dispose them for this use? and for this purpose they must be dissolved, as minutely divided as possible, and combined in such a manner that the imperfections of those which might be disposed to scale may be corrected by others.
Resins may be dissolved by three agents. 1. By fixed oil. 2. By volatile oil. 3. By alcohol. And accordingly we have three kinds of varnish: the fat or oily varnish, essential varnish, and spirit varnish. Before a resin is dissolved in a fixed oil, it is necessary to render the oil drying. For this purpose the oil is boiled with metallic oxides; in which operation the mucilage of the oil combines with the metal, while the oil itself unites with the oxygen of the oxide. To accelerate the drying of this varnish, it is necessary to add oil of turpentine. The essential varnishes consist of a solution of resin in oil of turpentine. The varnish being applied, the essential oil flies off, and leaves the resin. This is used only for paintings. When resins are dissolved in alcohol, the varnish dries very speedily, and is subject to crack; but this fault is corrected by adding a small quantity of turpentine to the mixture, which renders it brighter, and less brittle when dry.
We shall now give the method of preparing a number of varnishes for different purposes.
A Varnish for Toilet-boxes, Cases, Fans, &c.—Dissolve two ounces of gum mastic and eight ounces of gum sandarach in a quart of alcohol; then add four ounces of Venice turpentine.
A Varnish for Wainscots, Cane-chairs, Iron-chairs, Grates.—Dissolve in a quart of alcohol eight ounces of gum sandarach, two ounces of seed lac, four ounces of rosin; then add six ounces of Venice turpentine. If the varnish is wished to produce a red colour, more of the lac and less of sandarach should be used, and a little dragon's blood should be added. This varnish is so thick that two layers of it are equal to four or five of another.
A Varnish for Fiddles, and other Musical Instruments.—Put four ounces of gum sandarach, two ounces of lac, two ounces of gum mastic, an ounce of gum eleuni, into a quart of alcohol, and hang them over a slow fire till they are dissolved; then add two ounces of turpentine.
Varnish in order to employ Vermilion for painting Equipages.—Dissolve in a quart of alcohol fix ounces of sandarach, three ounces of gum lac, and four ounces of rosin; afterwards add six ounces of the cheapest kind of turpentine; mix with it a proper quantity of vermilion when it is to be used.
Gold-coloured Varnish.—Pound separately four ounces of stick lac, four ounces of gamboge, four ounces of dragon's blood, four ounces of annatta, and one ounce of saffron: put each of them separately into a quart of alcohol, and expose them for five days in a narrow-mouthed bottle to the sun, or keep them during that time in a very warm room, shaking them every now and then to hasten the solution. When they are all melted, mix them together. More or less of each of these ingredients will give the different tints of gold according as they are combined. In order to make silver imitate gold exactly when covered with this varnish, the quantity of ingredients must be somewhat greater. The method of gilding silver-leaf, &c. with this varnish is as follows: The silver-leaf being fixed on the subject, in the same manner as gold-leaf, by the interposition of proper glutinous matters, the varnish is spread upon the piece with a brush or pencil. The first coat being dry, the piece is again and again washed over with the varnish till the colour appears sufficiently deep. What is called gilt leather, and many picture frames, have no other than this counterfeit gilding. Washing them with a little rectified spirit of wine affords a proof of this; the spirit dissolving the varnish, and leaving the silver-leaf of its own whiteness. For plain frames, thick tinfoil may be used instead of silver. The tin-leaf, fixed on the piece with glue, is to be burnished, then polished with emery and a fine linen cloth, and afterwards with putty applied in the same manner: being then lacquered over with the varnish five or six times, it looks very nearly like burnished gold. The same varnish, made with a less proportion of the colouring materials, is applied also on works of brafs; both for heightening the colour of the metal to a resemblance with that of gold, and for preserving it from being tarnished or corroded by the air.
Oil Varnishes.—Gum copal and amber are the substances principally employed in oil varnishes; they possess the properties necessary for varnishes, solidity and transparency.—The copal being white, is used for varnishing light, the amber for dark colours. It is best to dissolve them before mixing them with the oil, because by this means they are in less danger of being scorched, and at the same time the varnish is more beautiful. They should be melted in a pot on the fire; they are in a proper state for receiving the oil when they give no resistance to the iron spatula, and when they run off from it drop by drop. The oil employed should be a drying oil, and perfectly free from grease. It should be poured into the copal or amber by little and little, constantly stirring the ingredients at the same time with the spatula. When the oil is well mixed with the copal or amber, take it off the fire; and when it is pretty cool, pour in a greater quantity of the essence of turpentine than the oil that was used. After the varnish is made, it should be passed through a linen cloth. Oil varnishes become thick by keeping; but when they are to be used, it is only necessary to pour in a little essence of turpentine, and to put them for a little on the fire. The turpentine is necessary in oil varnishes to make them dry properly; generally twice as much of it is used as of oil. Less is necessary in summer than in winter. Too much oil hinders the varnish from drying; but when too little is used, it cracks and does not spread properly. We shall subjoin the most useful oil varnishes:
White Copal Varnish.—On 16 ounces of melted copal pour four, fix, or eight ounces of linseed oil, boiled and quite free from grease. When they are well mixed, take them off the fire (not forgetting to stir them properly); and when pretty cool, pour in 16 ounces of the essence of Venice turpentine. Pass the varnish through a cloth.—Amber varnish is made in the same way.
Black Varnish for Coaches and Iron Work.—This varnish is composed of bitumen of Palestine, rosin, and amber, melted separately, and afterwards mixed: the oil is then added, and afterwards the turpentine, as directed above. The usual proportions are, 12 ounces of amber, two ounces of rosin, two ounces of bitumen, fix of oil, and 12 of the essence of turpentine.—Golden-coloured varnish may be made also by substituting linseed oil for alcohol.
Essential Oil Varnishes.—The only essential oil varnishes used are for pictures. Picture varnishes should be white, light, and quite transparent, which will preserve the colours without giving them any disagreeable tint; and it should be possible to take them off the picture without injuring it. They are usually made of gum mastic and turpentine dissolved together in some essential oil. The varnish is passed through a cloth, and allowed to clarify. It is applied cold to the picture.
Varnish for Glass, in order to preserve it from the Rays of the Sun.—Pulverise a quantity of gum adragant, and let it dissolve for 24 hours in the white of eggs well beat up; then rub it gently on the glass with a brush.
Varnishes before they are used should be carefully kept from dust, which would spoil them; and they should be kept in a vessel quite clean and dry. When used, they should be lifted lightly with a brush, and spread upon a ground altogether free from dirt and moisture. The substance, after being varnished, should be exposed to the heat of the sun, or placed in a warm room covered with a glass case, to keep out all filth. Oil varnishes require more heat than alcohol varnishes. The varnish should be put on very quickly, making great strokes with the pencil or brush, taking care that these strokes never cross one another; it should be spread equally, and never thicker than a leaf of paper; a second coat should never be put on till the first is quite dry. If the varnish, after being put on, becomes dull and uneven, it must be taken off entirely, and new varnish put on.
When wainscot is to be varnished, it is first painted of a wooden colour. This colour is made by infusing in water either red or yellow ochre (according to the colour wished for), terra ombria (a kind of ochre) and white lead; into this as much as necessary is put of parchment paste. Two thin coats of this are to be put on, and, after they are quite dry, the varnish.
Varnishes are polished with pumice-stone and tripoli earth. The pumice-stone must be reduced to an impalpable powder, and put upon a piece of serge moistened with water; with this the varnished substance is to be rubbed lightly and equally. The tripoli must also be reduced to a very fine powder, and put upon a clean woollen cloth moistened with olive oil, with which the polishing is to be performed. The varnish is then to be wiped with soft linen, and, when quite dry, cleaned with starch or Spanish white, and rubbed with the palm of the hand or with a linen cloth.
To recover colours or varnish, and to take off the dirt and filth which may adhere to them, a ley is used made of potash and the ashes of lees of wine. Take 48 ounces of potash, and 16 of the above-mentioned ashes, and put them into fix quarts of water, and the ley is made: instead of the ashes an equal quantity of potash would probably do as well. To clean dirty colours, dilute some of this ley with four times its quantity of water, and rub the picture with it; then wash it with river water; and when dry, give it a coat or two of varnish. In order to take off a varnish, wash it with the above-mentioned ley, then with water, and then lift it off the substance on which it was with any iron instrument.—We shall finish this article with a description of the famous Chinese varnish.
The Chinese varnish is not a composition, but a resin which exudes from a tree called in China shi-chu, "varnish tree." This tree grows in several provinces of the southern parts of China. The Chinese take the following method of propagating this tree: In spring they choose a vigorous shoot about a foot in length, which proceeds immediately from the trunk; and coat over the lower part, by which it adheres to the tree, with a kind of yellow earth, at least three inches in thickness. This coat is carefully covered with a mat, to defend it from rain and the injuries of the air. Towards the autumnal equinox they detach a little of the earth, to observe in what condition the small roots are, which begin to spring forth from the shoot. If they find that the filaments which compose them are of a reddish colour, they judge it is time to make an amputation; but they defer it if the roots are white, because this colour shows that they are yet too tender: they then close up the coat again, and wait till the spring following. When the shoot is separated from the trunk of the tree, it is put into the earth; but in whatever season it is planted, whether in spring or autumn, great care must be taken to put plenty of cinders into the hole prepared for it; without this precaution the ants would destroy the yet tender roots, or at least deprive them of all their moisture, and cause them to decay.
The Chinese do not procure varnish from the th-chu until its trunk is nearly five inches in diameter, which size it seldom attains to before seven or eight years. Varnish extracted from a tree smaller or of less age would not have the same body and splendour. This liquor distils only in the night time, and during the summer season. To cause the gum to flow, they make several rows of incisions round the trunk, the number of which is proportioned to the vigour of the tree. The first row is seven inches from the earth, and the rest are at the same distance one from the other, and continue to the top of the trunk, and even sometimes on the boughs which are of sufficient strength and size. The Chinese use a crooked iron for making these incisions, which must run a little obliquely, and be equal in depth to the thickness of the bark; they make them with one hand, and with the other hold a shell, the edges of which they insert into the opening, where it remains without any support. These incisions are made towards evening, and next morning they collect the varnish which has fallen into the shells; the following evening they are again inserted, and this operation is continued until the end of summer. A thousand trees yield almost in one night 20 pounds of varnish.
While the varnish distils, it exhales a malignant vapour, the bad effects of which can only be prevented by preservatives and great precaution. The merchant who employs the workmen is obliged to keep by him a large vase filled with rape-oil, in which a certain quantity of those fleshy filaments have been boiled that are found in hog's lard, and which do not melt. When the workmen are going to fix the shells to the trees, they carry some of this oil along with them, and rub their face and hands with it, which they do with greater care when they collect in the morning the varnish that has distilled during night. After eating, they wash their whole bodies with warm water, in which the bark of the chestnut tree, fir wood, crystallized saltpetre, and some other drugs, have been boiled. When they are at work near the trees, they put upon their heads a small cloth bag in which there are two holes, and cover the fore part of their bodies with a kind of apron made of doe-skin, which is suspended from their necks with strings, and tied round them with a girdle. They also wear boots, and have coverings on their arms, made of the same kind of skin. The labourer who should attempt to collect varnish without using this precaution, would soon be punished for his rashness, and the most dreadful effects would ensue. The disorder shows itself by tetter, which become of a bright red colour, and spread in a very short time; the body afterwards swells, and the skin bursts and appears covered with an universal leprosy. The unhappy wretch could not long endure the excruciating pain which he feels, did he not find a speedy remedy in those preservatives which are used against the malignant and noxious exhalations of the varnish.
The season of collecting varnish being ended, the merchant puts it into small casks closely stopped. A pound of it newly made costs him about one shilling and eight pence sterling; but he gains cent. per cent. upon it, and sometimes more, according to the distance of the place to which he transports it.
Besides the lustre and beauty which that varnish gives to many of the Chinese manufactures, it has also the property of preserving the wood upon which it is laid, especially if no other matter be mixed with it. It prevents it from being hurt either by dampness or worms.
Every workman has a particular art and method of using the varnish. This work requires not only much skill and dexterity, but also great attention, to observe the proper degree of fluidity which the gum ought to have, as it must be neither too thick nor too liquid when it is laid on. Patience above all is necessary in those who wish to succeed. To be properly varnished, a work must be done at leisure; and the whole summer is scarcely sufficient to bring it to perfection. It is therefore rare to see any of those cabinets which are imported to us from Canton so beautiful and durable as those manufactured in Japan, Tong-king, and Nang-king, the capital of the province of Kiang-nan: not that the artists do not employ the same varnish; but as they work for Europeans, who are more easily pleased, they do not take the trouble of giving the pieces which come from their hands all the polish they are capable of receiving.
There are two methods of laying on the varnish; the simplest is, when it is immediately laid on the wood. The work is first polished, and then daubed over with a kind of oil which the Chinese call tong-you. When this oil is dry, it receives two or three coats of varnish; which remain so transparent, that all the shades and veins of the wood may be seen through them. If the artist is desirous of entirely concealing the substance on which they are laid, nothing is necessary but to add a few more coats; these give the work a shining surface, the smoothness of which equals that of the most beautiful ice. When the work is dry, various figures are painted upon it in gold and silver, such as flowers, birds, trees, temples, dragons, &c. A new coat of varnish is then sometimes laid over these figures, which preserves them, and adds much to their splendour. The second method requires more preparation. The Chinese workmen fix to the wood by means of glue a kind of pasteboard, composed of paper, hemp, lime, and other ingredients, well beaten, that the varnish may incorporate with them. Of this they make a ground perfectly smooth and solid, over which the varnish is laid in thin coats, that are left to dry one after the other.
It often happens, that the lustre of varnished tables and other pieces of furniture is infensibly destroyed by tea and warm liquors. "The secret of restoring to varnish its shining black colour (says a Chinese author) is to expose it for one night to a white hoar-frost, or to cover it some time with snow." For a method of imitating Chinese varnish, see TURNING.
VARNISH also signifies a sort of shining coat, whereby with potters-ware, delft-ware, china-ware, &c. are covered, vered, which gives them a smoothness and lustre. Melted lead is generally used for the first, and small for the second. See GLAZING.
among medalists, signifies the colours antique medals have acquired in the earth.
The beauty which nature alone is able to give to medals, and art has never yet attained to counterfeit, enhances the value of them: that is, the colour which certain soils in which they have a long time lain tinges the metals withal: some of which are blue, almost as beautiful as the turquoise; others with an inimitable vermilion colour; others with a certain shining polished brown, vastly finer than Brasil figures.
The most usual varnish is a beautiful green, which hangs to the finest strokes without effacing them, more accurately than the finest enamel does on metals.
No metal but bras is susceptible of this; for the green rust that gathers on silver always spoils it, and it must be got off with vinegar or lemon juice.
Falsifiers of medals have a false or modern varnish, which they use on their counterfeits, to give them the appearance or air of being antique. But this may be discovered by its softness; it being softer than the natural varnish, which is as hard as the metal itself.
Some deposit their spurious metals in the earth for a considerable time, by which means they contract a sort of varnish, which may impose upon the less knowing; others use sal ammoniac, and others burnt paper.