Cobalt Yellow
Artificial inorganic pigmentComposition and Properties of Cobalt Yellow
Cobalt yellow is potassium cobaltinitrite K3[Co(NO2)6].
The stability of this pigment was subject to discussion since its first use. It has been reported to be fairly stable in watercolor use and not suitable for oil painting (1). The pigment is lightfast in watercolor paintings and is compatible with all inorganic pigments but should not under any circumstances be mixed with organic pigments.
Video: 'Lightfastness Testing Aureolin' by Dr. Oto Kano
Pigment
Painted swatch
Names of Cobalt Yellow
Alternative names
Aureolin
Color Index
PY 40, CI 77357
Word origin
Cobalt: From the German word Kobold meaning evil house spirit. The name was originated by medieval miners who believed, that cobalt ores made it difficult to extract silver from silver ore.
Aureolin: from Latin auereus = golden
Kobaltgelb
German
Jaune de cobalt
French
Giallo di cobalto
Italian
Amarillo de cobalto
Spanish
Preparation of Cobalt Yellow
The pigment can be prepared by mixing an acidic solution of a cobalt salt with a concentrated solution of potassium nitrite. The precipitate is then filtered, thoroughly washed and dried (1). The description of the first synthesis of this pigment by N.W. Fischer can be found in his original article in German (3). A thorough investigation of the methods of preparation was conducted more recently by G. Gates (2).
References
(1) Cornman, M., Cobalt Yellow (Aureolin), in Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 1: Feller, R.L. (Ed.) Oxford University Press 1986, pp. 37-46. Available as pdf from the National Gallery of Art.
(2) Glenn Gates, A Note on the Artists’ Pigment Aureolin, Studies in Conservation, Vol. 40, No. 3 (Aug. 1995), pp. 201-206
(3) N. W. Fischer, Ueber die salpetrichtsauren Salze, Annalen der Physik, Volume 150, Issue 5, pages 115–125, 1848, Article first published online: 5 Apr 2006, DOI: 10.1002/andp.18491500512
Video: 'Cobalt Yellow Pigment Synthesis - Aureolin' by The Alchemical Arts
Video: 'How to make Cobalt Yellow' by ophscomenius
History of Use
The pigment was discovered by N.W. Fischer in 1831 (2) and again independently rediscovered by Saint-Evre in 1851. It was not used broadly due to its unsatisfactory properties and high price (1).
References
(1) Cornman, M., Cobalt Yellow (Aureolin), in Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 1: Feller, R.L. (Ed.) Oxford University Press 1986, pp. 37-46. Available as pdf from the National Gallery of Art.
(2) N. W. Fischer, Ueber die salpetrichtsauren Salze, Annalen der Physik, Volume 150, Issue 5, pages 115–125, 1848, Article first published online: 5 Apr 2006, DOI: 10.1002/andp.18491500512
Identification
Fiber optics reflectance spectra (FORS)
Spectra by A. Cosentino, Cultural Heritage Science Open Source (CHSOS)
Raman Spectrum
Spectrum by Ian M. Bell, Robin J.H. Clark and Peter J. Gibbs, Raman Spectroscopic Library
University College of London
X-Ray Fluorescence Spektrum (XRF)
XRF Spectrum in the Free XRF Spectroscopy Database of Pigments Checker, CHSOS website.
Microphotograph
image © Volker Emrath
Further Reading
References
(1) Cornman, M., Cobalt Yellow (Aureolin), in Artists’ Pigments. A Handbook of Their History and Characteristics, Vol. 1: Feller, R.L. (Ed.) Oxford University Press 1986, pp. 37-46. Available as pdf from the National Gallery of Art.
(2) Glenn Gates, A Note on the Artists’ Pigment Aureolin, Studies in Conservation, Vol. 40, No. 3 (Aug., 1995), pp. 201-206
(3) N. W. Fischer, Ueber die salpetrichtsauren Salze, Annalen der Physik, Volume 150, Issue 5, pages 115–125, 1848, Article first published online: 5 Apr 2006, DOI: 10.1002/andp.18491500512
(4) S. Muntwyler, J. Lipscher, HP. Schneider, Das Farbenbuch, 2nd. Ed., 2023, alataverlag Elsau, pp. 96-97.