cobaltblue

Cobalt blue is a shade of blue named after cobalt salts used to produce the pigment. The term covers a family of cobalt-based pigments and the vivid blue color used in art, glass, and ceramics. The most historically important form is cobalt aluminate spinel, a pigment produced by combining cobalt oxide with aluminum oxide and firing at high temperature. A related material, smalt, is powdered cobalt glass used as a glaze pigment.

Chemistry and properties: Cobalt blue pigments are typically cobalt(II) aluminate CoAl2O4; they are valued for thermal and chemical stability, lightfastness, and an intense blue hue. Smalt consists of cobalt oxide dispersed in glass, yielding a deep blue glaze when dissolved, often used in medieval stained glass and underglaze decoration.

History and usage: The use of cobalt blue dates to ancient times in glass decorations in the Near East and Asia. It became widely associated with Chinese blue-and-white porcelain and later with European Delftware in the 17th century. In the 19th and 20th centuries, synthetic cobalt blue pigments became common in artists' paints and various industrial applications.

Applications and safety: Cobalt blue remains popular in ceramics, glassmaking, and oil and acrylic paints; its intense hue is also used in digital color approximations. Some cobalt compounds pose health hazards if inhaled or ingested; handling pigments requires standard safety precautions.