Page:A color notation (Munsell).djvu/59

 Spectral analysis shows that no pigment is a pure example of the dominant hue which it sends to the eye. Take, for example,

the very chromatic pigments representing red and green, such as vermilion and emerald green. If each emitted a single pure hue free from trace of any other hue, then their mixture would appear yellow, as when spectral red and green unite. But, instead of yellow, their mixture produces a warm gray, called brown or “dull salmon,” and this is to be inferred from their spectra, where it is seen that vermilion emits some green and purple as well as its dominant color, while the green also sends some blue and red light to the eye.

Thus stray hues from other parts of the spectrum tend to neutralize the yellow sensation, which would be strong if each of the pigments were pure in the spectral sense. Pigment absorption affects all palette mixtures, and, failing to obtain a satisfactory yellow by mixture of red and green, painters use original yellow pigments,—such as aureolin, cadmium, and lead chromate,— each of them also impure but giving a dominant sensation of yel- low. Did the eye discriminate, as does the ear when it analyzes the separate tones of a chord, then we should recognize that yel- low pigments emit both red and green rays.

White light dispersed into a colored band by one prism, may have the process reversed by a second prism, so that the eye sees again only white light. But this would not be so, did not the balance of red, green, and violet-blue sensations remain undisturbed. All our ideas of color harmony are based upon this fundamental relation, and, if pigments are to render harmonious effects,