the painter can, after some amount of trouble, arrive at results which are almost as accurate as those which could be deduced by a chemist. An expert on this question some years ago summarized the characteristics of colors which should be considered in making the examination, under the following heads:
1. Purity of the material.
2. Purity of the tone, brilliancy; richness, which indicates the amount of care in selection.
3. Fineness of grinding or preparation; this means the degree of the division of the particles and upon the completeness of such division will depend
4. Its spreading capacity.
5. Its body. This applies, of course, only to opaque or semi-opaque colors. Body is opacity, and means capacity to conceal the surface to which the paint is applied, and must not be confused with spreading. It is an inherent quality.
6. Its staining power or tinting strength with white or colors.
7. The quality of purity of the tint with white.
8. If a paste color, the consistency of the paste.
9. Transparency of transparent colors and the quality of the transparency.
10. The permanency of the color.
It will be observed that all of these tests will not necessarily be applied to every color. For instance, a transparent color would be tested for its transparency, but certainly not for its body. The one condition is the converse of the other.
Purity of the Material. This is sometimes of considerable importance, as in the case of white lead, whilst in others, for example the earth colors, it can hardly be said that there is a standard of purity. As a rule a knowledge of practical chemistry is necessary in order to determine whether a sample of paint or color is pure or not.
The purity of white lead, however, can readily be ascertained by the painter who possesses no chemical knowledge
