Cobalt blue is the cool blue color of the pigments made using cobalt salts of alumina. Cobalt blue pigments are extremely stable, and have historically been used as colouring agents in ceramics, (especially Chinese porcelain), jewellery, and paint. Transparent glasses are tinted with the silica-based cobalt pigment smalt.
Chemically, cobalt blue pigment is a cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. The compound is made by sintering finely ground CoO and Al2O3 (alumina) at 1200 °C. Cobalt blue is lighter and less intense than (iron-cyanide based) Prussian blue.
Read more about Cobalt Blue: Historical Uses and Production, Cobalt Blue in Human Culture, Toxicity
Famous quotes containing the word blue:
“So here they are, the dog-faced soldiers, the regulars, the fifty-cents-a-day professionals riding the outposts of the nation, from Fort Reno to Fort Apache, from Sheridan to Stark. They were all the same. Men in dirty-shirt blue and only a cold page in the history books to mark their passing. But wherever they rode and whatever they fought for, that place became the United States.”
—Frank S. Nugent (1908–1965)