CHAPTER V.

A PIGMENT COLOR SPHERE.[27]

+How to make a color sphere with pigments.+

(102) The preceding chapters have built up an ideal color solid, in which every sensation of color finds its place and is clearly named by its degree of hue, value, and chroma.

[Illustration: Fig. 16.]

It has been shown that the neutral centre of the system is a balancing point for all colors, that a line through this centre finds opposite colors which balance and complement each other; and we are now ready to make a practical application, carrying out these ideal relations of color as far as pigments will permit in a color sphere[27] (Fig. 16).

[Footnote 27: Patented Jan. 9, 1900.]

(103) The materials are quite simple. First a colorless globe, mounted so as to spin freely on its axis. Then a measured scale of value, specially devised for this purpose, obtained by the daylight photometer.[28] Next a set of carefully chosen pigments, whose reasonable permanence has been tested by long use, and which are prepared so that they will not glisten when spread on the surface of the globe, but give a uniformly mat surface. A glass palette, palette knife, and some fine brushes complete the list.

[Footnote 28: See paragraph 65.]

(104) Here is a list of the paints arranged in pairs to represent the five sets of opposite hues described in Chapter III., paragraphs 61-63:--

_Color Pairs._ _Pigments Used._ _Chemical Nature._

Red and Venetian red. Calcined native earth. Blue-green. Viridian and Cobalt. Chromium sesquioxide.

Yellow and Raw Sienna. Native earth. Purple-blue. Ultramarine. Artificial product.

Green and Emerald green. Arsenate of copper. Red-purple. Purple madder. Extract of the madder plant.

Blue and Cobalt. Oxide of cobalt with alumina. Yellow-red. Orange cadmium. Sulphide of cadmium.

Purple and Madder and cobalt. See each pigment above. Green-yellow. Emerald green See each pigment above. and Sienna.

(105) These paints have various degrees of hue, value, and chroma, but can be tempered by additions of the neutrals, zinc white and ivory black, until each is brought to a middle value and tested on the value scale. After each pair has been thus balanced, they are painted in their appropriate spaces on the globe, forming an equator of balanced hues.

[Illustration: Fig. 17.]

(106) The method of proving this balance has already been suggested in