PB28
Cobalt Blue is an artificial mineral pigment, produced by the calcination of cobalt oxide and aluminium oxide. It has been widely used since the early 1800s, following its discovery by the French chemist Thenard at the beginning of the century. The name Cobalt has its roots in the German word Kobold, meaning imp or evil spirit. German miners named it to in the late-Middle Ages, as the presence of cobalt ore in the mines made the extraction of silver more difficult. They were possibly also aware of the toxic properties of the mineral that was frustrating their efforts.
Cobalt remains a very popular colour today, and is present in most ranges of paints, being a semi-transparent pigment that is stable in all media. As a watercolour, all cobalt pigments tend to granulate. As an oil paint, it requires less oil content than most other pigments, and dries quite quickly. Like Cerulean Blue, some artists may choose to bind it with poppy oil, to avoid any possible colour changes brought about by the yellowish cast of linseed oil and the pigment's weak tinting strength.
Limeproof
Toxicity: C
