Varnishes of this description are call changing because, when applied to metals such as copper, brass, or tin or silver foil, they give them a more agreeable colour; indeed, the common metals, when coated with them acquired a lustre approaching to that of the precious metals, and hence these varnishes are much employed in manufacturing imitations of gold and silver. Put four ounces of the best gum gamboge into 32 ozs. of spirits of turpentine, 4 ozs. of dragon's blood into the same quantity of spirits of turpentine as the gamboge, and 1 oz. of anatto into 8 ozs. of the same spirits. The three mixtures being made in different vessels, they should then be kept for about a fortnight in a warm place, and as much exposed to the sun a possible; at the end of that time they will be fit for use; and you can procure any tints you wish by making a composition from them, with such proportions of each liquor as practice and the nature of the colour you are desirous of obtaining will point out. Changing varnishes may likewise be employed, with very good effect, for furniture, such as picture frames, &c.—See Lackers.
103. GOLD LACKER OR VARNISH
In using the changing varnish or any of these lackers, for picture frames for instance, lay them over with tin or silver leaf, by means of plaster of Paris glue, or cement of some kind, that the foil may be perfectly adherent to the wood, then apply your varnish; apply as many coats as may suit your taste, and if it be the gold lacker you use it has the appearance of being laid with gold leaf, and if the pale brass lacker, of being laid with brass, &c., and if you use the changing varnish you may make it just what colour you wish, by mixing the three materials in different proportions. For making gold lacker, put into a clean 4 gallon tin 1 lb. ground turmeric, 1-1/2 oz. powdered gamboge, 3-1/2 lbs. powdered gum sandrack, 3/4 lb. shellac, and 2 galls. spirits of wine; after being dissolved and strained add 1 pint of turpentine varnish, receipt No. 112, well mixed, and it is ready for use.
104. RED SPIRIT LACKER
Take 2 galls. spirits of wine, 1 lb. dragon's blood, 3 lbs. Spanish annatto, 3-1/2 lbs. gum sandrack, 2 pints turpentine. Made exactly as the gold lacker.
105. PALE BRASS LACKER
Take 2 galls. spirits of wine, 3 ozs. cape aloes, cut small, 1 lb. fine pale shellac, 1 oz. gamboge, cut small, no turpentine. Varnish made exactly as before, but observe, that those who make lackers frequently want some paler and some darker and sometimes inclining more to the particular tint of certain of the component ingredients; therefore if a 4 oz. vial of a strong solution of each ingredient be prepared, a lacker of any tint can be prepared at any time as by changing varnish.
106. DEMAR VARNISH
This is a fine clear varnish, being harder and less coloured than mastic, while it is as soluble, and may be had at one-tenth the price. Put 6 oz. of gum demar in a bottle with 10 ozs. of spirits of turpentine, and put into another bottle 6 ozs. of gum demar, with 16 ozs. alcohol, when they are dissolved put them together, and you have an excellent cheap varnish which dries quickly and is very clear.