White Pigments

White Pigments. The most important of these is white lead, which not only is very serviceable when used alone as a white colour, but in oil-painting most other colours are mixed with it to give them body. Commercial white lead is frequently mixed with sulphate of baryta (barium sulphate), but manufacturers of white lead object to this being called an adulteration, as the mixture is sold by them as such. Less common adulterations are Gypsum (q.v.), chalk, and china clay. Flake White is a pure white lead specially prepared for artists, and keeps its colour better than the kind commonly used by house-painters (see LEAD, and PIGMENTS). Zinc White, or oxide of zinc, is not so much used for artistic work in oil as flake white, but in house-painting it is often coated over a ground of white lead, zinc white not being liable to change by the action of sulphuretted hydrogen. As an oil-colour it wants body, and is a bad dryer. As a water-colour, under the name of Chinese white, it is very useful and permanent. Baryta White, permanent white, is the sulphate of baryta, and is best when artificially prepared. This pigment does not change in impure air, but is not much in favour for oil-painting, except to mix for some purposes with white lead, as it renders it less liable to alter in tint. White pigments are numerous, but these three are by far the most important.