[868] XIV. Coloring Plaster Molds.

Manufacturer and Builder 2, 1874

— How can I give to plaster molds a delicate flesh-colored tint? Also how can I give them the tint of either arterial or venous blood? The object is to make costs of anatomical preparations and pathological specimens. Can stained glass be successfully treated by pigments? How could the effect of stained glass windows be cheaply produced in stage scenery?
— S. H.

— You may either mix the plaster before hand with a cheap coloring material, or paint it afterward, in which case you may use more expensive paints, as then little is wanted. The flesh colors used for flesh tints are vermilion, carmine, sulphid of cadmium, etc., either alone or combined and mixed with sufficient Paris white, so as to obtain the right tone of color. It is also necessary to give your plaster object first a few coats of dissolved starch, dextrin, guns, or glue, in order to close the pores, as otherwise the color sinks too much into the porous plaster. The color should also be mixed with the same, as otherwise it comes of easily. The arteries are painted with vermilion, the veins with ultramarine or Prussian blue mixed with white, as pure Prussian blue is too dark. The whole is then afterward varnished, so as to make it waterproof. You may also use oil colors from the start, in which case you simply buy at an artist store some tin tubes with the prepared painta, and proper brushes. But in this case your plaster object is best coated first with boiled linseed oil, as a basis of gluewater coating is very apt to cause the oilpaint put on, afterward to peel off, if the object is exposed to moisture. You can stain glass successfully with pigments, provided you do not take opaque ones, but such as are transparent—no vermilion, chrome yellow, or ultramarine, but carmine, anilin red, gamboge, Prussian blue, etc., all put on in a sufficiently thin coating; the first are better used as water colors, the Prussian blue as an oil paint. The effects of stained glass is easily produced on stage scenery; stained ground glass by thin paper oiled and colored; ordinary glass by films of colored glue or gelatin, easily made by putting the proper coloring material in a clear glue solution, and pouring this on a plate of glass like a photographer coats the glass negative with collodion. When dry, it easily peels off, and in this way a great number of very cheap colored films may be produced, which, when set in stage windows, looks exactly like glass stained with different colors; and being slightly flexible, are not as fragile as glass. If exposed to a very dry atmosphere, however, they may become brittle. In such cases it is well to add during the preparation a very small quantity of glycerin to the glue, say one per cent, so as to prevent the too great hardness and consequent brittleness in a very dry locality. Too much glycerin would prevent it from ever drying.