This color contains the following pigments:
cobalt(II) oxide + aluminum oxide
CoO + Al2O3
Cobalt blue is a semitransparent pigment with low to moderate tinting strength. When it dries, it appears lighter and less saturated. Pigment particles are large and grainy. Differences in how the pigment is ground and mixed lead to considerable differences in its performance among various manufacturers.
Cobalt blue is absolutely lightfast and extraordinarily stable. The stability of cobalt salts at high temperatures make them the standard for blues used in ceramics and glassware.
Cobalt salts are toxic. Avoid respiratory and skin contact. Soluble cobalt may cause irritation and allergic reaction through contact with skin. It is considered a possible carcinogen.
Since ancient times, smalt blue has been used to color glass and ceramics. Cobalt salts, which give smalt its characteristic blue color, were identified in the 18th century. Techniques for manufacturing Cobalt Blue, a chemically pure salt of cobalt and aluminum oxide, were developed in 1802.
beta copper phthalocyanine
Phthalo Blue PB15:3 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.