This color contains the following pigments:
CoO n SnO2
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.
Phthalo Blue PB15:2 is a structural variant of Phthalo Blue PB15 that produces more greenish tones.
Phthalo Blues are completely lightfast and stable and are permanent for all paint uses. They are currently used in inks, coatings, and many plastics due to their stability and are considered a standard pigment in printing ink and the packaging industry.
Phthalo Blues have no significant hazards, although those made before 1982 contained some PCBs (polychlorinated biphenyls).
Developed by chemists using the trade name Monastral Blue, the organic blue dyestuff now known as Phthalo Blue was presented as a pigment in November 1935 in London. Its discovery was accidental. The dark color was observed in a kettle where a dye was being made from a British dyestuff plant. The demand for such a pigment came from commercial printers who wanted a cyan to replace Prussian Blue.