aureolin

{{Short description|Yellow pigment used in painting}}

{{Infobox color

| title=Aureolin

| hex=FDEE00

| source=[https://html-color.codes/hex/fdee00 HTML Color Codes]

| isccname=Vivid greenish yellow

}}

Aureolin (sometimes called cobalt yellow) is a pigment sparingly used in oil and watercolor painting. Its color index name is PY40 (40th entry on list of yellow pigments). It was first made in 1831 by Nikolaus Wolfgang Fischer in Breslau characterizing it as "Doppelsalze" or double-salts{{cite journal | doi = 10.1002/andp.18310970114 | title = Ueber Stickstoffoxyd-Salze | year = 1831 | last1 = Fischer | first1 = N. W. | journal = Annalen der Physik und Chemie | volume = 97 | issue = 1 | pages = 160–163| bibcode = 1831AnP....97..160F | url = https://onlinelibrary.wiley.com/doi/abs/10.1002/andp.18310970114 }} and its chemical composition is potassium cobaltinitrite. He characterized it again and wrote more extensively about it in 1842, naming it "Salpetrichtsaures Kobaltoxydkali".{{cite journal |last1=Fischer |first1=N. W. |title=Ueber die salpetrichtsauren Salze |journal=Annalen der Physik |date=1848 |volume=150 |issue=5 |pages=115–125 |doi=10.1002/andp.18491500512 |bibcode=1848AnP...150..115F |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/andp.18491500512 |access-date=27 May 2021}} In 1851–1852, Edouard Saint-Evre synthesized cobalt yellow independently.{{cite journal |last1=Saint-Evre |first1=Edouard |title=Recherches sur une combinaison nouvelle du cobalt |journal=Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences |date=1852 |volume=35 |pages=552–555 |url=https://gallica.bnf.fr/ark:/12148/bpt6k2992n/f556# |access-date=27 May 2021}} He is credited with the introduction of cobalt yellow as an artists pigment.{{Cite book|last=Feller|first=Robert L.|url=http://www.nga.gov/content/dam/ngaweb/research/publications/pdfs/artists-pigments-vol1.pdf|title=Artists' Pigments, A Handbook of Their History and Characteristics|publisher=National Gallery of Art, Washington; Archetype Publications, London|year=1986|isbn=978-1-904982-74-6|location=|pages=37–38}} The investigation by Gates gives the exact modern procedures for the preparation of aureolin and also the methods for its identification in paintings.{{cite journal | jstor = 1506479 | pages = 201–206 | last1 = Gates | first1 = G. | title = A Note on the Artists' Pigment Aureolin | volume = 40 | issue = 3 | journal = Studies in Conservation | year = 1995 | doi = 10.2307/1506479}}
- {{cite book | url = https://books.google.com/books?id=bdQVgKWl3f4C&pg=PA109 | title = Painting materials: A short encyclopaedia | isbn = 978-0-486-21597-6 | author1 = Gettens, Rutherford John | author2 = Stout, George Leslie | year = 1966 | pages =109–110| publisher = Courier Corporation }}

Aureolin is rated as permanent in some reports but there are other sources which rate it as unstable in oils but pronounce it stable in watercolors.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, p. 37-46 Others find it unstable in watercolors, fading to greyish or brownish hues.[http://www.handprint.com/HP/WCL/watery.html#PY40 Pigments: aureolin] It is a transparent, lightly staining, light valued, intense medium yellow pigment.

It is a rather expensive pigment and sold by several manufacturers of oil paints such as Grumbacher, Michael Harding, and Holbein. However, the pigment was never popular as an oil color and is much more widely available as a watercolor from manufacturers such as: Winsor & Newton, Talens Rembrandt, Rowney Artists, Sennelier, Art Spectrum and Daniel Smith.