Cobalt blue
Chinese potters used cobalt for a thousand years. In 1802 a French chemist made it a painter's blue.
- Made from
- Cobalt oxide and alumina
- Invented
- Louis Jacques Thénard, 1802
- Name
- From kobold, a mine goblin
Cobalt colored glass and pottery blue long before anyone knew the metal existed. It gave Chinese blue-and-white porcelain its blue from about the 8th or 9th century, and European glassmakers ground cobalt glass into a weak blue pigment called smalt. German miners called the troublesome ore kobold, a goblin, because it held no useful metal and gave off poisonous arsenic fumes when smelted, the element later behind the arsenic greens. In the 1730s chemists showed it contained a new metal, named cobalt after the goblin.
The bright pigment came from a government order. The French state wanted a cheaper rival to ultramarine, and in 1802 the chemist Louis Jacques Thénard produced cobalt aluminate, a clean, stable, slightly cool blue. Commercial production began in 1807, and watercolorists soon recommended it for skies.
Painters from Turner to the Impressionists and Van Gogh used it. Renoir's The Umbrellas shows how pigments can date a painting: scientists at London's National Gallery found the parts painted around 1881 use vivid cobalt blue, while the parts he repainted around 1885–86 use a greyer mix based on ultramarine.
The app's cobalt is a strong, slightly cool mid blue, darker than azure and less violet than ultramarine. Like many bright pigments, the real thing is toxic if swallowed or inhaled. In 2009, chemists at Oregon State found YInMn blue, whose bluest form matches cobalt's color without its toxicity.
Swatches
- Cobalt blue · Thénard, 1802
- Smalt · cobalt glass, ground (approx.)
Colors
Sources
- Bomford, D. et al. (1990). Art in the Making: Impressionism. National Gallery, London.
- National Gallery, London. Renoir's The Umbrellas: pigment analysis.
- Wikipedia, 'Cobalt blue' and 'Cobalt'.
Hex values are screen approximations. Every page lists its sources.