Mars Black is an opaque black with a strong and cool masstone, a slightly warm tint, and a warm brown undertone. It is not as black as Ivory Black, but it dries more quickly and has three times the tinting strength. Mars Black is normally the only black available in acrylic form and that is safe to over paint. It can be used in all media without reservation and is widely used as an alternative to Lamp Black and Ivory Black.
Mars Black is very lightfast with excellent permanence.
Mars Black has no significant hazards and is the only major black pigment considered non-toxic.
The word Mars refers to the Roman god of iron and war. Mars Black was developed in the early 20th century from inorganic, synthetic iron oxide.
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Cerulean Blue is the standard cool blue, considered the traditional counterpart to Ultramarine, and is often used for painting atmospheric shades. It is quick drying and retains its color well, better than any other blue, in oil paint form. However, it tends to granulate or become chalky in watercolors. It has limited hiding power, is semi-opaque, and is easy to control. Its tinting capacity is low, so it can become lost when mixing.
Cerulean Blue has excellent permanence. It is very stable and lightfast.
Cerulean Blue is moderately toxic if inhaled or ingested and slightly toxic if it comes into contact with skin.
The name Cerulean Blue comes from the Latin word caelum, meaning sky. This pigment was discovered in 1805 by Andreas Hopfner, but it was not widely available until introduced by Messrs. G. Rowney & Co. in England under the name coeruleum in 1860 for use in aquarelle and oil painting. It was produced by the action of heat on cobalt oxide and other metallic bases.