This section is from the book "Chromatography; Or, A Treatise On Colours And Pigments, And Of Their Powers In Painting", by George Field. Also available from Amazon: Chromatography, or A Treatise on Colours and Pigments, and of Their Powers in Painting.
Bone Brown And Ivory Brown are produced by torrefying, or roasting, bone and ivory till by partially charring they become of a brown colour throughout. They may be made to resemble the live first browns above by management in the burning; and, though much esteemed by some artists, are not perfectly eligible pigments, being had dryers in oil; and their lighter shades not durable either in oil or water when exposed to the action of strong light, or mixed in tint with white lead. The palest of these colours are also the most opaque: the deepest are more durable, and most so when approaching black.