Lacker for brass like French polish is made in a great variety of ways, and as in French polish the simplest and best pale lacker for works that do not require to be coloured, consists of shell lac and spirits of wine only, in the proportions of about 1/2 lb. of the best pale shell lac to 1 gallon of spirit. Lacker is required to be as clear and bright as possible; it is therefore always made without heat by continuous agitation for five or six hours. The lacker is then allowed to stand until the thicker portions are precipitated, when the clear lacker is poured off, and if it should not be sufficiently clear, it is afterwards filtered through paper into a bottle, which should be kept closely corked and out of the influence of light which would darken the colour of the lacker. This may however be easily prevented by pasting paper round the bottle.
Lackers are frequently required to be coloured either of yellow or red tints. For yellow tints turmeric, cape aloes, saffron or gamboge are employed, and for red tints annotto and dragon's blood are used; the proportions being varied according to the colour required. Thus, for a pale yellow, about 1 ounce of gamboge and 2 ounces of cape aloes are powdered and mixed with 1 lb. of shell lac. For a full yellow, 1/2 lb. of turmeric and 2 ounces of gamboge, and for a red lacker, 1/2 lb. of dragon's blood and 1 lb. of annotto. The colour is also modified by that of the lac employed, the best pale or orange shell lac being used for light coloured lackers, and darker coloured shell lac, or seed lac, is used for the darker tints. For pale lackers sandarac is sometimes used with the shell lac. Thus a pale gold-coloured lacker is made with 8 ounces of shell lac, 2 ounces of sandarac, 8 ounces of turmeric, 2 ounces of annotto, and 1/4 ounce of dragon's blood to 1 gallon of spirits of wine.
The most convenient method, however, of colouring lackers, is to make a saturated solution in spirits of wine of each of the colouring matters, and to add the solutions in different proportion to the pale lacker according to the tint required, but the whole of the colouring matters are not generally used by the same makers, and solutions of turmeric, gamboge, and dragon's blood, afford sufficient choice for ordinary purposes. The turmeric gives a greenish yellow tint, and with the addition of a little gamboge, is the colouring matter employed in making the so called green lacker used for bronzed works, as noticed at page 1413.
Another mode of making lacker is followed by Mr. A. Ross: 4 ounces of shell lac and 1/4 ounce of gamboge are dissolved by agitation without heat in 24 ounces of pure pyro-acetic ether. The solution is allowed to stand until the gummy matters not taken up by the spirit subside, the clear liquor is then decanted, and when required for use is mixed with eight times its quantity of spirits of wine. In this case, the pyro-acetic ether is employed for dissolving the shell lac in order to prevent any but the purely resinous portions being taken up, which is almost certain to occur with ordinary spirits of wine, owing to the presence of water; but if the lacker were made entirely with pyro-acetic ether, the latter would evaporate too rapidly to allow time for the lacker to be equally applied.
Mastic varnish for paintings, and similar purposes, is sometimes made in small quantities with spirits of wine; but more generally oil of turpentine is employed as the solvent, the proportion being about 3 lbs. of 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, and 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 is liable to chill, and the surface frequently remains tacky for some time after the bb2 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 may be 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 pearlash; the sand is afterwards to be washed three or four times with hot water, and strained each time. The sand is afterwards 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 4 lbs. of common resin dissolved in 1 gallon of oil of turpentine, it requires no other preparation than sufficient warmth to dissolve the resin; sometimes the 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, coloured prints, and drawings. A very good crystal varnish is made with 2 lbs. of mastic and 2 lbs. of damar, dissolved without heat in 1 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 colourless, flow freely, and are moderately 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.