Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminium(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) 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) |
| HSV (h, s, v) | (215°, 100%, 67%) |
| CIELChuv (L, C, h) | (33, 82, 259°) |
| Source | [Unsourced] |
| ISCC–NBS descriptor | Vivid blue |
| B: Normalized to [0–255] (byte) | |
| Identifiers | |
|---|---|
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.100.107 |
| EC Number |
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PubChem CID
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| Properties | |
| Al2CoO4 | |
| Molar mass | 176.892 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Historical uses and production
editOres 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 in Chinese porcelain.[1] In 1742, Swedish chemist Georg Brandt showed that the blue color was due to a previously unidentified metal, cobalt. The first recorded use of cobalt blue as a color name in English was in 1777.[2] It was independently discovered as an 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.
Cobalt glass is used decoratively, and also as an optical filter to remove or hide certain visible colors.
In human culture
edit- 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]
- 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).
- 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, partially famous for the intensity of his skyscapes, frequently used cobalt blue, and as a result cobalt blue sometimes is called Parrish blue.
- Cobalt blue is a commonly used color for interior decorating.[7]
- Because of its chemical stability in the presence of alkali, cobalt blue is used as a pigment in blue concrete.
- Two Major League Soccer teams have cobalt blue as a secondary color: Real Salt Lake from its inception,[8] and Sporting Kansas City on its home uniforms since 2008.[9]
- Several countries including the Netherlands and Romania, and a U.S. state – Nevada – have cobalt blue as one of three shades of their flags.
- Sega's official logo color is cobalt blue. Sonic the Hedgehog, Sega's current mascot, was colored to match.[10]
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An example of cobalt blue hue (not pure cobalt blue) -
Pierre-Auguste Renoir, Boating on the Seine (La Yole), c. 1879
Toxicity
editCobalt blue is toxic when ingested or inhaled. Its use requires appropriate precautions to avoid internal contamination and to prevent cobalt poisoning.
Natural occurrence
editA single record of the compound concerns inclusions in sapphires from a single site.[11]
See also
editReferences
edit- ^ 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.
- ^ 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
- ^ 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), "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.
- ^ "Chinese pottery: The Yuan dynasty (1206–1368)". Archived 2017-12-29 at the Wayback Machine Encyclopædia Britannica Online. Accessed 7 June 2018.
- ^ ""J Varley's List of Colours". The British Museum. Archived from the original on 2016-09-20. Retrieved 2016-07-22.
- ^ "Cobalt blue". ColourLex. Archived from the original on 2015-04-15. Retrieved 7 June 2018.
- ^ Cobalt Blue Is the Vibrant Shade You Need for 2023
- ^ "Real Salt Lake unveil new primary kit for 2018". MLSSoccer.com. February 8, 2018. Retrieved June 26, 2019.
- ^ "History". SportingKC.com. Retrieved June 26, 2019.
- ^ 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
- ^ "UM1994-06-O:AlCo".
Further reading
edit- 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
External links
edit
- "History of Cobalt blue". Pigments through the Ages. WebExhibits.
- Cobalt blue – ColourLex
- An Archaeometallurgical Explanation for the Disappearance of Egyptian and Near Eastern Cobalt-Blue Glass at the end of the Late Bronze Age – Internet Archaeology