Cobalt blue
Cobalt blue is a cool, slightly desaturated blue color, historically made using cobalt salts of alumina. It is used in certain ceramics (historically, especially Chinese porcelain) and painting; the different cobalt pigment smalt, based on silica, is more often used directly in tinted transparent glasses. The pigment is extraordinarily stable.
Chemically, cobalt blue is a cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. The compound is made by sintering the stoichiometric mixture of finely ground CoO and Al2O3 (alumina) at 1200°C.
Cobalt blue in impure form had long been used in Chinese porcelain,[1] but was independently discovered as a pure alumina-based pigment by Louis Jacques Thénard, in 1802.[2] Commercial production began in France in 1807. The first recorded use of cobalt blue as a color name in English was in 1777.[3] The leading world manufacturer of cobalt blue in the 19th century was Blaafarveværket ("blue-color works," in Dano-Norwegian) in Norway, led by Benjamin Wegner. Germany was also famous for production- especially the Blaufarbenwerke ("blue-color works," in German) of Schneeburg. The dye is not to be confused with Prussian blue, which is an intensely-blue pigment based on iron and cyanide, that contains no cobalt.
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[edit] Cobalt blue in human culture
- John Varley suggested cobalt blue as a good substitution for ultramarine blue for painting skies.
- 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.[4]
- Because of its chemical stability in the presence of alkali, cobalt blue is used as a pigment in blue concrete.
- 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, common in most flames (as even the most trace amount of it is very overpowering).
- "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.
- Major League Soccer's Kansas City Wizards have had cobalt blue as the secondary color of its home uniforms since 2008.[5]
- Several countries, like the Netherlands and Romania, have cobalt blue as one of three shades of their tricolour.
[edit] 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.
[edit] See also
[edit] References
- ^ 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.
- ^ 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.). http://books.google.de/books?id=UGsMAQAAIAAJ&pg=RA1-PA506. (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", Journal des Mines 86: 128–136, http://annales.ensmp.fr/articles/1803-1804-1/71-75.pdf.
- ^ Maerz and Paul A Dictionary of Color New York:1930 McGraw-Hill Page 91; Color Sample of Cobalt Blue: Page 131 Plate 34 Color Sample L7
- ^ "Chinese visual arts » Stylistic and historical development, 1206–1912 » Yüan dynasty (1206–1368) » Ceramics." Encyclopædia Britannica Online. Accessed 14 May 2009.
- ^ "Wizards unveil new look for '08 season," Kansas City Wizards Media Relations, January 20, 2008.
[edit] External links
- "History of Cobalt blue". Pigments through the Ages. WebExhibits. http://webexhibits.org/pigments/indiv/history/coblue.html.
