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:
“Sometimes we see a cloud that’s dragonish,
A vapor sometimes like a bear or lion,
A towered citadel, a pendant rock,
A forked mountain, or blue promontory
With trees upon ‘t that nod unto the world
And mock our eyes with air. Thou hast seen these signs;
They are black vesper’s pageants.”
—William Shakespeare (1564–1616)