Asian Art

Cobalt blue

Cobalt blue is a blue pigment consisting principally of cobalt(II) aluminate, CoAl2O4, made by sintering cobalt(II) oxide with aluminium(III) oxide (alumina) at high temperatures. It is used as a ceramic color, in automotive and industrial coatings, in scientific and medical imaging, and as a fine-art pigment. Its thermostability, chemical inertness, and lightfastness make it suitable for applications requiring a durable blue color. Before the development of cobalt blue, the primary cobalt-based pigment was smalt, a blue pigment made by grinding cobalt-containing glass. Smalt is of relatively weak tinting strength and can exhibit poor lightfastness in some formulations. The development of cobalt blue, together with the rising demand for strongly tinting and highly saturated pigments from the 19th century, contributed to the decline of smalt as a paint pigment. Smalt however, remains popular as a glass colorant.

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See also

• ▸Iwai Hanshirō VIII
• ▸Barteria
• ▸Bank of Tokyo-Mitsubishi UFJ Money Museum

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