Cobalt blue

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Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with alumina at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl₂O₄. Cobalt blue is lighter and less intense than the (iron-cyanide based) pigment Prussian blue. It is extremely stable and has historically been used as a coloring agent in ceramics (especially Chinese porcelain), jewelry, and paint. Transparent glasses are tinted with the silica-based cobalt pigment smalt.

Video Cobalt blue

Historical uses and production

Cobalt blue in impure forms had long been used in Chinese porcelain, but it was independently discovered as a pure alumina-based pigment by Louis Jacques Thénard in 1802. Commercial production began in France in 1807. The first recorded use of cobalt blue as a color name in English was in 1777. The leading world manufacturer of cobalt blue in the 19th century was Benjamin Wegner's Norwegian company Blaafarveværket, ("blue colour works" in Dano-Norwegian). Germany was also famous for production, especially the blue colour works (Blaufarbenwerke) in the Ore Mountains of Saxony.

Maps Cobalt blue

In human culture

Art

• Watercolorist and astrologer John Varley suggested cobalt blue as a good substitution for ultramarine for painting skies, writing in his "List of Colours" from 1818: "Used as a substitute for Ultramarine in its brightness of colour, and superior when used in skies and other objects, which require even tints; used occasionally in retrieving the brightness of those tints when too heavy, and for tints in drapery, etc. Capable, by its superior brilliancy and contrast, to subdue the brightness of other blues."
• Cobalt blue has been used in paintings since its discovery by Thénard by painters such as Turner, the Impressionists such as Renoir, Monet and Post-Impressionists such as Van Gogh. It is stable and lightfast and also compatible with all other pigments.
• Maxfield Parrish, famous partly for the intensity of his skyscapes, used cobalt blue, and cobalt blue is sometimes called Parrish blue as a result.
• Cobalt blue was the primary blue pigment used in Chinese blue and white porcelain for centuries, beginning in the late 8th or early 9th century.

Automobiles

• Several car manufacturers including Jeep and Bugatti have cobalt blue as paint options.

Construction

• Because of its chemical stability in the presence of alkali, cobalt blue is used as a pigment in blue concrete.

Glassmaking

• The blue seen on many glassware pieces is cobalt blue, and it is used widely by artists in many other fields.
• Cobalt glass almost perfectly filters out the bright yellow emission of ionized sodium.

Ophthalmology

• Cobalt blue is used as a filter used in ophthalmoscopes, and is used to illuminate the cornea of the eye following application of fluorescein dye which is used to detect corneal ulcers and scratches.

Sports

• Two Major League Soccer teams have cobalt blue as a secondary color: Real Salt Lake from its inception and Sporting Kansas City on its home uniforms since 2008.

Vexillology

• Several countries including the Netherlands and Romania, and a U.S. state - Nevada - have cobalt blue as one of three shades of their flags.

Video Games

• Sega's official logo color is cobalt blue. Sonic the Hedgehog, Sega's current mascot, was colored to match.

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Toxicity

Cobalt blue is toxic when inhaled or ingested. Potters who fail to take adequate precautions when using cobalt blue may succumb to cobalt poisoning.

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See also

• List of colors
• List of inorganic pigments
• Cobalt glass

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References

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Further reading

• Roy, A. "Cobalt blue", in Artists' Pigments, Berrie, B.H., Ed., National Gallery of Art Washington, 2007

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External links

• "History of Cobalt blue". Pigments through the Ages. WebExhibits. 
• Cobalt blue ColourLex

Source of article : Wikipedia