2. All paint is composed of two general ingredients, namely, the pigment and the fluid medium. The former usually consists of a mineral oxide or precipitated vegetable dye, which very largely forms the body of the paint, and determines its color, while the latter consists of the oil, varnish, or water in which the pigment is dissolved or suspended, according to the character of which, the paint is termed oil color or water color.

Oil colors are used in all places where the purpose of the paint is to protect as well as to decorate the surface to which it is applied, or where the painted decorations are likely to be exposed to the elements. Water colors are used in house painting exclusively for decorative effects, and then only in places where they will not be subjected to dampness or strong sunlight.

3. Pigments are, according to the base from which they are derived, divided into several classes. The metallic oxides give us pigments of various colors, some of which are of great importance to the painter, while others, owing to their chemical influence on other pigments, cannot be mixed to form compound colors.

Various salts of lead produce white, red, and yellow pigments, the most important of which are the whites, as hereafter described. Iron and mercury produce red pigments. The oxides of cobalt give us a valuable shade of blue, and copper forms the base of a number of the most important greens.

The ochers, umbers, siennas, etc. are all forms of earth, found in their natural state, already mixed with certain mineral oxides, which impart to them the colors by which they are known.

4. Lakes

Lakes. This is the general term given to those pigments, derived from animal, vegetable, or coal-tar coloring matter. They are usually, according to their particular composition, prefixed by another name to more clearly define them, such as crimson lake, madder lake, etc., madder being the name of that group of pigments made from the coloring matter of the madder root.

5. Carmines

Carmines. These pigments are the coloring matter which is derived from cochineal, and they form several combinations with madders and lakes, which will be hereafter discussed.

A knowledge of the metallic bases of the various pigments is, then, most important, as upon their intelligent use and admixture depend the permanence and brilliancy of the resulting colors.