Varnishes are solutions of the various resins, commonly called gums, in either oil, turpentine, or alcohol. The gums principally applied are amber, anime, copal, lac, Sandarac, mastic, damar and common resin. The varnishes are all applied to the surfaces of the woods, metals, or other materials, while in the fluid state, and the solvent is afterwards evaporated, leaving a thin glossy coat of the different resins as a defence from the action of the atmosphere, or from slight friction.

Sometimes the resins are used separately; at other times two or more are combined according to the qualities required in the varnish.

Mastic Varnish, for painting, and similar purposes, is sometimes made in small quantities with spirit of wine; but, more generally, oil of turpentine is employed as the solvent, the proportion being about three pounds ot mastic to the gallon of turpentine. For the best varnish, the mastic is carefully picked and dissolved by agitation without heat, exactly as for the best white hard varnish; after the mastic varnish has been strained it is poured into a bottle, which is loosely corked and exposed to the sun and air for a few weeks; this causes a precipitation, from which the clear varnish may be poured off for use; but the longer the varnish is kept the better it becomes.

Mastic varnish works very freely, but it is liable to chill, and the surface frequently remains tacky for some time after the varnish is applied. To prevent the latter evil, it is recommended, before dissolving the mastic, to bruise it slightly with a muller, and pick out all the pieces that are too soft to break readily, and which maybe used for common varnish. To prevent the chilling, which arises from the presence of moisture, Mr. W. Neil recommends a quart of river sand to be boiled with two ounces of pear-lash; the sand is afterwards to be washed three or four times with hot water, and strained each time. The sand is then to be dried in an oven, and when it is of a good heat, half a pint of the hot sand is to be poured into each gallon of varnish, and shaken well for five minutes; it is then allowed to settle, and carries down the moisture of the gum and turpentine.

In making common varnish, heat is generally employed to dissolve the mastic, and about one pint of turpentine varnish is added to every gallon of varnish.

Turpentine Varnish is made with four pounds of common resin dissolved in one gallon of oil of turpentine. It requires no other preparation than sufficient warmth to dissolve the resin. Sometimes resin and turpentine are mixed together in a stone or tin bottle, which is placed near the fire, or in a sand-bath over a stove, and shaken occasionally; but varnish-makers generally mix the resin and turpentine in the gum-pot, and employ sufficient heat to fuse the resin. This is a more expeditious practice, but is attended with some danger of fire. When a very pale turpentine varnish is required, bleached resin is used, and care is taken not to employ more heat than is necessary in making the varnish. Turpentine varnish is principally used for in-door painted works and common painted furniture and toys. It is also frequently added to other varnishes to give them greater body, hardness, and brilliancy.

Crystal Varnish is a name frequently given to very pale varnishes employed for paper works - such as maps, colored paints, and drawings. A very good crystal varnish is made with two pounds of mastic and two pounds of damar, dissolved without heat in one gallon of turpentine. Another good but more expensive crystal varnish is made with equal quantities of Canada balsam and oil of turpentine. In making this varnish, it is only necessary to warm the Canada balsam until it is quite fluid, then add the turpentine and shake the mixture for a few minutes until the two are thoroughly incorporated. The varnish may then be placed in a moderately warm situation for a few hours, and will be ready for use on the following day. These crystal varnishes are both nearly colorless, flow freely, and are more flexible, so as to bear bending or rolling, and either of them may be employed to make a tracing paper of middling quality, by applying a thin coat of varnish on one or both sides of any thin transparent paper, such as good tissue or foreign post paper.

Paper Varnish, for paper hangings and similar purposes, is made with four pounds of damar to one gallon of turpentine. The damar dissolves very readily in the turpentine, either with moderate agitation or a very gentle heat. Sometimes white or bleached resin is used instead of the damar, or the two are combined.

Water Varnish

All the varieties of lac may be dissolved in nearly boiling water by the addition of ammonia, borax, potash, or soda, but these alkalies all have the effect of rendering the color of the lac much darker. The solutions, may, however, be employed as varnishes, which when dried will resist the application of water sufficiently well to bear washing, especially when the proportion of alkali employed is only just sufficient to cause the dissolution of the lac, and which is also desirable in order to keep the varnish as light-colored as possible. The least color is given with diluted water of ammonia, in the proportions of about sixteen ounces of ordinary water of ammonia to seven pints of water and two pounds of pale shell-lac, to which about four ounces of gum Arabic may be added. Borax is, however, more generally used, and the proportions are then two pounds of shell-lac, six ounces of borax, and four ounces of gum Arabic to one gallon of water. When the varnish is required to be as light-colored as possible, while lac is employed.

Sealing-wax Varnish, for coating parts of electrical machines and similar purposes, is made by dissolving two and a half pounds of good red sealing-wax and one and a half pound of shell-lac in one gallon of spirit of wine.

Black Varnish may be made with three pounds of black sealing-wax and one pound of shell-lac to the gallon of spirit, or fine lampblack may be mixed with brown hard varnish or lacker, according to the thickness required in the varnish. The interior of telescope tubes are frequently blackened with a dull varnish of this kind, made by mixing lampblack with rather thick brass lacker, as little of the lampblack being employed as will serve to deaden the bright color of the lacker. Mathematical instruments are sometimes blackened with a similar thin varnish, and the surface is afterwards brightened with one or two coats of lacker applied as usual. Ordinary lampblack, however, generally contains greasy impurities and moisture, which render it unfit for varnish purposes, and therefore the best kind should be employed, or the lampblack should be purified by ramming it hard into a close vessel, and afterwards subjecting it to a red heat. In the workshop, when small quantities of lampblack are required, it is frequently made for the occcasion, by placing a piece of sheet metal over the flame ot an oil lamp. A black varnish, sometimes used for metal works, is made by fusing three pounds of Egyptian asphaltum, and, when well dissolved, half a pound of shell-lac and one gallon of turpentine are added.

Varnish For Iron

Take 2 lbs. pulverized gum asphaltum, ¼ lb. gum benzoin, 1 gallon spirits of turpentine. To make this varnish quickly, keep in a warm place and shake often till it is dissolved. Shade to suit with finely ground ivory black. Apply with a brush. This varnish should be used on iron work, exposed to the weather. It is also well adapted for inside work, such as iron furniture, where a handsome polish is desired.

Varnish For Cane And Basket-Work

Lac, prepared after the following recipe is used to cover split and colored cane: 25grs. of good linseed oil are heated in a sand-bath, as long as a drop of it, poured on a cold stove, does not run when the stone is inclined, and when touched with the finger it feels thready. Then is added first in small portions, 1 lb. fat copal varnish, and the vessel wherein the copal varnish is heated must be large, because by the addition of the linseed oil, a great deal of frothing takes place. When cold, the required consistence is given to the varnish by mixing it with turpentine oil. It soon dries, preserves a sufficient elascity, and may be applied with or without addition of colors.