Cobalt
- HEX
- #0047AB
- RGB
- 0 71 171
- HSL
- 215° 100% 34%
- CMYK
- 100 58 0 33
Cobalt or Denim?
A deep, vivid blue, much more vivid than denim.
Language
Cobalt is named after a goblin. German miners called a troublesome ore kobold: it gave off poisonous arsenic fumes when smelted and yielded none of the metal they wanted. In the 1730s the Swedish chemist Georg Brandt showed it held a new metal, the one that turns glass blue.
History
In 1802 the French chemist Louis Jacques Thénard heated cobalt with alumina and got a deep, stable blue. Cobalt blue gave painters a reliable, affordable rival to ultramarine. See cobalt-blue-pigment.
Culture
Centuries earlier, cobalt made China's blue-and-white porcelain. In the 14th century, under the Mongol Yuan dynasty, potters at Jingdezhen painted with cobalt brought from Persia, then sealed it under a clear glaze. The style sailed the world and was copied from Delft to Iznik.
Art
Painters fell for cobalt in the 1800s. It was one of the Impressionists' new synthetic colors: Monet painted the snow of Lavacourt in almost pure cobalt, and Van Gogh called it a divine color for putting atmosphere around things. It also helped unmask a forger: Han van Meegeren's fake Vermeers contained cobalt blue, a pigment Vermeer never had.
Science
Cobalt colored glass long before paint. Egyptian glassmakers used it for deep blue, and the 12th-century windows of Saint-Denis and Chartres owe their blue to it. Ground cobalt glass, called smalt, was a cheap painter's blue from the 1500s, but it dulled in oil. The 'lost' blue of Chartres is a myth: the recipe is known; the old kilns are what can't be copied.
Kin
- White: Cobalt on white porcelain: China's blue-and-white
- Powder blue: Smalt, ground cobalt glass, was the first 'powder blue'
- Cerulean: A cobalt pigment with tin added, lighter and greener
- Azure: Cobalt blue was the affordable answer to lapis ultramarine
In paintings
- The Starry Night, Vincent van Gogh
Sources
- Royal Society of Chemistry, Periodic Table, 'Cobalt'
- Royal Talens, 'Cobalt blue: from fake silver to colourful pigment'
- Jesus College Cambridge, 'Branding Jingdezhen blue-and-white porcelain in the fourteenth century'
- Ball, Bright Earth: The Invention of Colour (2001)
- St Clair, The Secret Lives of Colour (2016)
- Finlay, Color: A Natural History of the Palette (2002)
- Pastoureau, Blue: The History of a Color (2001)
- Gage, Colour and Culture (1993)
Hex values are screen approximations. Every page lists its sources.