Oil painting materials and techniques: Chemical Changes of Pigments
Chemical Changes of Pigments The causes of change of color in pigments are of four kinds, all of them chemical effects. 1) the action of light; 2) the action of the atmosphere; 3) the action of the medium, and 4) the action of the pigments themselves on each other. The action of light is to bring about or to assist in the decomposition of the pigment. It is less marked in oil than in water color, because the oil forms a sort of sheath for the color particles. The manner in which light does its deteriorating work is somewhat similar to that of heat. The atmosphere affects the paint because of certain chemical elements contained in…