It must be admitted that it is very disappointing to a painter to find, after taking pains to produce the exact color required, that it flies or fades after a little exposure to the weather. The tests for the permanence of a color when exposed to light are simple enough, and are to mix a little of the colors to be tested in oil and to spread them on different slips of paper, cut the paper in half, number each half with corresponding figures or letters, expose one half to a stroug light for as long as may be deemed desirable and put the other half away into a safe place where the light does not penetrate. Waxed paper is the best, as it will not absorb the thinners, or, better still, glass may be used, this being cut across with a diamond after the paint has been applied. It need hardly be said that the permanence of water colors is entirely different from that of oil colors. As far as pigments are concerned, yellow ochres, siennas, umber, Vandyke brown and the earth colors generally are permanent, as are Venetian red, Indian red, chrome yellow and lemon yellow.

Ultramarine, Prussian blue and vermilion are also permanent or nearly so.