Description
A clear blue pigment. (Some early varieties possessed a greenish tinge.) Cobalt blue is composed of a double oxide of cobalt and aluminum, also called cobaltous aluminate. It is resistant to weathering, sunlight, acids, and alkalis. Though possibly discovered earlier, the process for making cobalt blue by heating cobalt phosphate with alumina was first published by L.J.Thénard in France in 1803/4 based on experiments he had carried out in 1802. Leithner discovered an alternate process for making cobalt blue from cobalt arsenate and alumina. By the early 19th century, cobalt blue was sold as an artists pigment as a replacement for smalt and ultramarine, although it has always been relatively costly. The pigment has been identified in French and British paintings as early as 1806/07. In recent years, the cobalt blue hue has been imitated using mixtures of ultramarine and phthalocyanine. The saturated cobalt blue color in glazes and glassware is produced by cobalt oxide.
Synonyms and Related Terms
cobalt aluminate; Pigment Blue 28; CI 77346; Thénard's blue; Kobaltblau (Deut.); bleu de Thénard (Fr.); bleu de cobalt (Fr.); cobaltblauw (Ned.); blu di cobalto (It.); blu di Therard (It.); mple toy kobaltioy (Gr.); azul de cobalto (Esp.); azul cobalto (Port.); cobalt ultramarine; cobaltous aluminate; king's blue; Olympia blue; Vienna blue; Vienna ultramarine; Leyden blue; Hungary blue; Dresden blue; azure cobalt; Gahn's blue; Leithner blue; new blue;
Other Properties
Irregular to rounded blue particles with a ‘crusty’ surface, no birefringence, no pleochroism. Appears red through Chelsea filter.
Unaffected by acids, alkalis, light, and heat.
Strong siccative properties in oil on account of the cobalt content.
Hazards and Safety
Skin contact may cause allergies, especially on elbows, neck and ankles. Chronic inhalation may cause asthma.
Ingestion may cause vomiting, diarrhea and the sensation of hotness.
Additional Information
° A. Roy, “Cobalt Blue”, Artists’ Pigments: A Handbook of Their History and Characteristics, Volume 4, B. Berrie (ed.), Archetype Publications, London 2007.
° Pigments Through the Ages: Cobalt blue
Record content reviewed by EU-Artech November 2007.
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Last updated on: 7/26/2009 10:26:32 AM
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