Cobalt blue is abluepigment made bysinteringcobalt(II) oxide withaluminium(III) oxide (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) pigmentPrussian blue. It is extremely stable, and has historically been used as a coloring agent in ceramics (especiallyChinese porcelain), jewelry, and paint. Transparentglasses are tinted with the silica-based cobalt pigment "smalt".
Ores containing cobalt have been used since antiquity as pigments to give a blue color to porcelain and glass. Cobalt blue in impure forms had long been used inChinese porcelain.[1] In 1742, Swedish chemistGeorg Brandt showed that the blue color was due to a previously unidentified metal, cobalt. The first recorded use ofcobalt blue as a color name inEnglish was in 1777.[2] It was independently discovered as an alumina-based pigment byLouis Jacques Thénard in 1802.[3] Commercial production began in France in 1807. The leading world manufacturer of cobalt blue in the nineteenth century wasBenjamin Wegner's Norwegian companyBlaafarveværket ("blue colour works" in Dano-Norwegian). Germany was also famous for production of it, especially the blue colour works (Blaufarbenwerke) in theOre Mountains ofSaxony.
Cobalt glass is used decoratively, and also as anoptical filter to remove or hide certain visible colors.
Cobalt blue was the primary blue pigment used for centuries in Chineseblue and white porcelain, beginning in the late eighth or early ninth century.[4]
Traditional Bunzlauer pottery made by Germans from Bunzlau also made an extensive use of cobalt blue glaze. The pigment was used along with white in classic patterns of blue and white dots before the synthetic production of more variously colored pigments (yielding such colors as green, red, orange).
WatercoloristJohn Varley suggested cobalt blue as a good substitution forultramarine 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 is toxic when ingested or inhaled. Its use requires appropriate precautions to avoid internal contamination and to preventcobalt poisoning.
^Kerr, Rose; Wood, Nigel (2004),Science and Civilisation in China Volume 5. Part 12, Ceramic Technology, Cambridge: Cambridge University Press, pp. 658–692,ISBN0-521-83833-9.
^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
^Sheffield, Brandon."Out of the Blue: Naoto Ohshima Speaks". Gamasutra.Archived from the original on 16 July 2015. Retrieved12 August 2013.Well, he's blue because that's Sega's more-or-less official company color
Roy, A. "Cobalt blue", inArtists' 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 Archaeology52doi:10.11141/ia.52.3,Internet Archaeology
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