To paint the skin of an animal, and yet make it look as if the skin contained the color instead of bearing it upon its surface, use oil colors, mix with boiled linseed oil and turpentine, equal parts, and apply. When the paint is beginning to dry, so that it is sticky, take some dry color of a corresponding tint, dip into it a clean, dry, square-ended bristle brush of good size, and twirl it about until it becomes filled with the dry powder, then, with light and delicate strokes, apply it directly upon the painted surface so that the dry color will fall upon the wet paint like a shower of colored dust. This is to be done with the motion that painters use in "stippling," and may very well be done with a stippling brush, if you have one. Do not get on too much of the dry color, or the effect will be spoiled. Your eye must teach you when to stop. In this process of stippling dry color into wet paint, plaster Paris may very frequently be used to good advantage to deaden gloss, and soften effects. In coloring the hairless portions of the faces, hands, etc., of apes, baboons, and monkeys, and on many other subjects, this process is of very great value.
Blending Colors.—If two colors are laid down, one against the other, each in a solid mass, up to the imaginary line that lies between them, the effect is hard and unpleasing, because unnatural. Nature never joins two contrasting-colors without a blending together and softening of the two tones where they touch each other. If it be red and brown, the red merges a little way into the brown, imperceptibly, perhaps, and the line of demarcation between the two is thus softened, and naturalized, if you please. Therefore, in your painting have no hard lines where your colors meet, but always blend adjoining colors together by passing a small brush over the line where they meet.
Strength of Tones.—The colors that Nature puts on an animal are not hard, crude, and staring, like bright red in the mouth of a mounted quadruped, but they are always in harmony with the other parts of the object. A bird may have yellow legs, but if it does, you may be sure they will not be a bright, glossy, chrome yellow, so gaudy as to instantly catch the eye. The chances are, they will be Naples yellow, with only a tinge of chrome. Learn to soften tints so they will not be staring, gaudy, and offensive to the eye. Examine the tongue of a live tiger or lion, and you will notice its color is a pale pink.
In all painting, study the harmony of colors, the strength of tones, and the blending of tints. Do not get your colors too gaudy, too sharply contrasted, nor laid on roughly; but paint evenly, and keep all your colors in perfect harmony.
Painting the Skin of Thinly Haired Mammals.—It very often happens that the skin of a thin-haired mammal has a decided color of its own, which must be imparted to it by painting. This is particularly the case with our next of kin—the apes and monkeys. The orang utan has a chocolate-colored skin, except the old males, in which it is black; the mona monkey has a bluish skin, and the faces of nearly all primates require painting. To paint a skin through thin hair, use oil colors mixed with turpentine, and made so thin that the mixture runs over the skin as soon as it touches it, like water. By separating the hair, it is often possible to get the paint on the skin without saturating the hair save at its roots; but if the turpentine color does get on the hair it must be sponged off with benzine. Do not mix your colors with oil, or you will get into serious trouble; but the oil in which the tube color has been ground will be just sufficient to give a natural tone to the skin. If the color when put on appears too strong and conspicuous, stipple the surface with a little plaster Paris, to tone it down.
Painting Legs and Beaks of Birds.—Paint the legs and beaks of such birds as require it, with a mixture of boiled linseed oil and turpentine, equal parts of each, and have your paint thin enough on the legs that it will not obscure the scales. On the beak, a thicker coat is necessary, and, in fact, it is nearly always necessary to put on two coats. In coloring the beaks of toucans and hornbills, blend adjoining colors very deeply but evenly, and let there be no hard boundary lines anywhere. A little white wax softened and cut with turpentine and mixed with the paint on a bird's beak gives the color a depth and transparency quite similar to the appearance of the beak of a living bird.
Painting Mounted Fishes.—A fish must be perfectly dry before it is touched with a brush. Time spent in painting a half-dry specimen is so much thrown away. The repairs with papier-maché must be complete and dry, and the specimen perfectly clean. Nearly every fish possesses in its coloring pigment a quality which imparts to it a silvery, metallic lustre; therefore, to secure the finest result attainable in painting a fish, either an actual specimen or a plaster cast, all those that are silvery must first be coated over the entire scaly surface with nickel leaf, laid on sizing, similar to the treatment of gold leaf in gilding.
With dark-colored fishes satisfactory work may be done without the use of nickel leaf, except on the under parts, which are nearly always silvery white. It is absolutely impossible to reproduce the brilliant lustre so characteristic of white scales by the use of white paint alone, or even silver bronze, or silver paint. Without the nickel underneath the paint looks dead and artificial. If you are called upon to make a large collection with as little outlay as possible, it will be sufficient to omit the nickel leaf, for your paint will still faithfully record the colors. But if you wish to have your fish look as brilliantly beautiful as when taken struggling from the water, put on the leaf first, and paint on it, thinly, so that the silver will show through your colors and impart to them the desired lustre. If you paint too thickly, the leaf will be covered up, and its lustre obscured.
Do not attempt to use silver bronze, silver paint, or even silver leaf, for nickel leaf is the only substance which has sufficient lustre and will not oxidize, and turn yellow.
If the whole body of a fish is dark, and without silvery tints, it is, of course, unnecessary to use leaf, for the lustre can be obtained by varnishing over the paint.