Cobalt blue

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 historically, has 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.

Cobalt blue
 
A sample of a commercial cobalt blue pigment
    Color coordinates
Hex triplet#0047AB
sRGBB  (r, g, b)(0, 71, 171)
CMYKH   (c, m, y, k)(100, 58, 0, 33)
HSV       (h, s, v)(215°, 100%, 67%)
Source[Unsourced]
ISCC–NBS descriptorVivid blue
B: Normalized to [0–255] (byte)
H: Normalized to [0–100] (hundred)

Historical uses and production

Cobalt blue in impure forms had long been used in Chinese porcelain.[1] The first recorded use of cobalt blue as a color name in English was in 1777.[2] It was independently discovered as a pure alumina-based pigment by Louis Jacques Thénard in 1802.[3] Commercial production began in France in 1807. The leading world manufacturer of cobalt blue in the nineteenth century was Benjamin Wegner's Norwegian company Blaafarveværket ("blue colour works" in Dano-Norwegian). Germany also was famous for production of it, especially the blue colour works (Blaufarbenwerke) in the Ore Mountains of Saxony.

In human culture

Art

  • Cobalt blue was the primary blue pigment used for centuries in Chinese blue and white porcelain, beginning in the late eighth or early ninth century.[4]
  • Watercolorist 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."[5]
  • Cobalt blue has been used in paintings since its discovery by Thénard, by painters such as J. M. W. Turner, Impressionists such as Pierre-Auguste Renoir and Claude Monet, and Post-Impressionists such as Vincent van Gogh.[6] 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 as a result, cobalt blue sometimes is called Parrish blue.

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.

Sports

Vexillology

Video games

  • An example of cobalt blue hue (not pure cobalt blue)
  • Pierre-Auguste Renoir, Boating on the Seine (La Yole), c. 1879

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.

See also

References
  1. Kerr, Rose; Wood, Nigel (2004), Science and Civilisation in China Volume 5. Part 12, Ceramic Technology, Cambridge: Cambridge University Press, pp. 658–692, ISBN 0-521-83833-9.
  2. Maerz and Paul. A Dictionary of Color. New York (1930). McGraw-Hill. p. 91; Color Sample of Cobalt Blue: Page 131 Plate 34 Color Sample L7
  3. Gehlen, A.F. (1803). "Ueber die Bereitung einer blauen Farbe aus Kobalt, die eben so schön ist wie Ultramarin. Vom Bürger Thenard". Neues allgemeines Journal der Chemie, Band 2. H. Frölich. Archived from the original on 2018-02-10. German translation from Thénard, L.J. (1803 (Brumaire, XII)), "Considérations générales sur les couleurs, suivies d'un procédé pour préparer une couleur bleue aussi belle que l'outremer" (PDF), Journal des Mines, 86: 128–136, archived (PDF) from the original on 2012-03-29 Check date values in: |year= (help).
  4. "Chinese pottery: The Yuan dynasty (1206–1368)". Archived 2017-12-29 at the Wayback Machine Encyclopædia Britannica Online. Accessed 7 June 2018.
  5. ""J Varley's List of Colours". The British Museum. Archived from the original on 2016-09-20. Retrieved 2016-07-22.
  6. "Cobalt blue". ColourLex. Archived from the original on 2015-04-15. Retrieved 7 June 2018.
  7. "Real Salt Lake unveil new primary kit for 2018". MLSSoccer.com. February 8, 2018. Retrieved June 26, 2019.
  8. "History". SportingKC.com. Retrieved June 26, 2019.
  9. Sheffield, Brandon. "Out of the Blue: Naoto Ohshima Speaks". Gamasutra. Archived from the original on 16 July 2015. Retrieved 12 August 2013. Well, he's blue because that's Sega's more-or-less official company color

Further reading
  • Roy, A. "Cobalt blue", in Artists' Pigments, Berrie, B. H., Ed., National Gallery of Art, Washington, D.C., 2007
  • Wood, J.R. and Hsu Yi-Ting, 2019, An Archaeometallurgical Explanation for the Disappearance of Egyptian and Near Eastern Cobalt-Blue Glass at the end of the Late Bronze Age, Internet Archaeology 52, Internet Archaeology
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