In testing a color for covering power or opacity, for coloring strength, and for brilliancy, comparison should always be made with a strictly standard color.
To assay for covering power or opacity, weigh out, say 50 grains, of the standard color and the same number of grains of the color under examination, and to each sample add 10 grains of fine china clay, if the colors be dark, or 10 grains of the highest grade of lampblack (this being a pure black) should they be light, and mix intimately. The sample which departs the least from its own color has the best body or covering power. Or mix exactly equal quantities of the standard color and the color to be assayed, in equal quantities of raw linseed oil, incorporating the oil and the pigment thoroughly, and then apply to glass surfaces (small panes of window glass answer the purpose fully), spreading the pigment as evenly as possible. The sample covering the glass most solidly has the strongest covering power.
Coloring power is determined by mixing a given quantity of a standard sample of color with a certain quantity of china clay or, if preferred, zinc white. Of the sample to be assayed take the same quantity of color and mix with exactly the same quantity of china clay or zinc white used with the standard. The sample showing the greatest depth of color may be accepted as having the strongest coloring power.
The durability or permanency of a pigment may be tested by mixing the pigment with raw linseed oil, spreading on a piece of glass, exposing it to the rigors of the weather, and noting its condition from time to time.
The fineness of a color or pigment can be judged by rubbing the material between two thick pieces of glass or subjecting it to a powerful microscopic examination. Or a common fruit can with a tight cover may be two-thirds filled with clean water, half an ounce of color put therein, and the contents vigorously shaken. The finer the sample is ground, the longer the time it will require to settle out.
The following table is intended to aid in the compounding of the principal hues, tints, and shades of colors used in carriage and wagon painting. It would prove futile to try to make the proportions arbitrary, because the uniformity of colors advocated above does not universally obtain, the product of one firm differing from that of other firms and very often, unfortunately, lacking uniformity in itself.
Moreover, color sense has not reached a uniform development, and the proportions which would, for example, make a cherry red as accepted by one person might not appear that color to the second person. However, in most of the formulas proportions are indicated, and the table is presented not as an infallible guide, but more in the nature of a reliably helpful one.
TABLE OF HUES, TINTS, AND SHADES OF COLORS.
REDS.
Transparent Red—No. 40 carmine.