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Cobalt Blue
#0047AB · click to copy
Cool
HEX
#0047AB
RGB
0, 71, 171
CMYK
100%, 58%, 0%, 33%
Pigment
PB28
Lightfastness
Excellent (I) — one of the most permanent blue pigments
Moods & Keywords
blue
bright
pure
calm
impressionist
sky
permanent
Impressionist
cobalt
cool
blue
permanent
Impressionist
cobalt
cool
blue
Pigment & Material
PB28
Synthetic
Cobalt(II) aluminate (CoAl₂O₄). Stable, lightfast, and slightly warm — one of the most reliable blues in an artist's palette.
Origin & History
Cobalt blue was developed by Louis Jacques Thénard in 1802 and quickly adopted by painters as a superior alternative to the expensive ultramarine and the somewhat unstable Prussian blue. It became the defining blue of Romantic and Impressionist painting — its clear, sky-like quality and excellent permanence made it ideal for outdoor painting.
Also Known As
Cobalt Blue
Thénard's Blue
Leithner Blue
Saxon Blue
Psychology
Clear, open, and serene. Cobalt blue is the blue of a clear sky at noon — not the deep blue of night, not the pale blue of dawn, but the definitive, unambiguous blue of a perfect day. It is among the most psychologically calming of all colours, associated with clarity, trustworthiness, and the limitless expanse of sky.
In Culture
Cobalt blue is the standard blue of Delftware pottery and Chinese blue-and-white porcelain (the cobalt was imported to China from Persia). It is the blue of police uniforms in many countries, chosen for its associations with authority and calm. In architectural glass, cobalt oxide has been used since antiquity — the windows of Chartres Cathedral use cobalt-containing glass.
Natural Sources
No natural source as a pigment — cobalt aluminate (CoAl₂O₄) is synthesised by heating cobalt oxide with aluminium oxide at high temperature. Smalt (ground cobalt-containing glass) is an earlier cobalt blue, but cobalt aluminate pigment was developed in 1802 by French chemist Louis Jacques Thénard.
Making It Yourself
Cobalt blue is synthesised industrially at high temperature — not practically available for home production.
Historical smalt (earlier cobalt blue):
1. Melt potash, silica, and cobalt oxide together at high temperature
2. Cool and grind the resulting blue glass
3. Mix with oil — produces smalt, the original cobalt glass blue
Note: smalt particle size affects colour; coarser = more intense; finer = weaker.
Historical smalt (earlier cobalt blue):
1. Melt potash, silica, and cobalt oxide together at high temperature
2. Cool and grind the resulting blue glass
3. Mix with oil — produces smalt, the original cobalt glass blue
Note: smalt particle size affects colour; coarser = more intense; finer = weaker.
Art Movements
Neoclassicism
Romanticism
Impressionism
Post-Impressionism
Famous Works
Monet
Impression, Sunrise, 1872
Van Gogh
Starry Night, 1889 (combined with Prussian blue)
Renoir
numerous figure paintings
Cézanne
landscape sky passages
Available As
Winsor & Newton — Cobalt Blue (PB28)
Daniel Smith — Cobalt Blue (PB28)
Old Holland — Cobalt Blue
M. Graham — Cobalt Blue
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Colour data compiled with AI. Spot an error or have more to add? Leave a Note — ekphra reviews and updates.
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