The process may be divided into five principal operations: 1. Preparation of the glass and marble plates; 2. Preparation of the glue solutions; 3. Pouring the colored solutions upon the plates; 4. Transferring the layer of glue to the layer of gelatine; and 5. Drying the veneers and detaching them from the plates.
1. Preparation of the plates. Both marble and glass plates are used for imitations of marble, but glass plates only for imitations of mother-of-pearl. The glass plates must be ground, but need not exceed O.11 to O.15 in. in thickness, and only require careful washing and drying for imitations of mother-of-pearl. For imitations of marble they should be rubbed with an oiled linen rag. Other glass plates, after being washed and polished with elutriated rouge and water, are wiped with a soft rag to remove any particle of the polishing powder. The polished surface is then gently rubbed with a rag dipped in pure Spanish chalk, and the excess of chalk carefully dusted off.
2. Preparation of the glue solutions. For one dozen plates, each 10¾ square feet, soak 2 lbs. of good, colorless glue in water for 24 hours, pour off the water and melt the glue in a water-bath and stir in 3½ ozs. of glycerine. For imitating marbles of two colors, compound 20 to 24 fluidounces of this glue solution with the quantities of thoroughly ground mineral colors given below; the rest of the glue solution is mixed with 6.34 ozs. of zinc white ground very fine. For imitating marble of three colors mix 14 fluidounces of the glue solution with one of the coloring matters and 14 fluidounces with the other coloring matter, and the remainder with zinc white. For imitating marble with four colors, take 10 fluidounces of the glue solution to each of the three coloring matters, and mix the rest with 4½ ozs. of zinc white.
The proportions by weight of the mixtures for 10 different varieties of imitations of marble and enamel are as follows:—
a. Mix 20 fluidounces of the glue solution with 1¾ ozs. of rouge and 2½ ozs. of zinc white, and the rest of the glue solution with 6⅓ ozs. of zinc white.
b. Mix 20 fluidounces of the glue solution with 1¾ ozs. of rouge, and the rest of the glue solution with 5¼ ozs. of zinc white.
c. Mix 14 fluidounces of the glue solution with 1¼ ozs. of zinc white and 1 oz. of rouge, 14 fluidounces of the glue solution with 1 oz. of yellow ochre, and the rest with 5¼ ozs. of zinc white.
d. Mix 14 fluidounces of the glue solution with 1 oz. of rouge, 14 fluidounces of the glue solution with ¾ oz. of sepia, and the rest with 5¼ ozs. of zinc white.
e. Compound 20⅓ fluidounces of the glue solution with 1 oz. of quite concentrated and filtered solution of aniline black, and the rest with 6⅓ ozs. of zinc white.
f. Mix 10 ozs. of the glue solution with 0.8 oz. of rouge, 10 fluidounces of the glue solution with 0.8 oz. of yellow ochre, 10 fluidounces of the glue solution with 0.8 oz. of sepia, and the rest with 4¼ ozs. of zinc white.