Chrome yellow
The first cheap brilliant yellow, and the reason Van Gogh's sunflowers are turning brown. Chrome yellow gave the nineteenth century a colour it had never had, and then began, slowly and irreversibly, to take it back.
Origin
Chromium was discovered in 1797 by Louis Nicolas Vauquelin, who isolated it from the mineral crocoite and immediately noticed that its compounds were intensely coloured — chroma, colour, is the root of the name. Lead chromate was proposed as a pigment shortly after and reached commercial production around 1809, once chromium ores were found in quantity in the Urals and later in North America. By varying the preparation, manufacturers produced everything from a pale primrose to a deep orange, sold as lemon, primrose, middle and deep chrome, and chrome orange. It was cheap, strong and immediately everywhere — including on the vehicles that gave the American school bus its colour.
In art history
It appears in eight eras of this atlas, and its most famous user is Van Gogh, who built the Sunflowers, the Yellow House and the wheat fields from it, in several grades at once, because it was the only affordable colour that could do what he wanted. Turner used it. The Impressionists used it. It is the yellow of nineteenth-century painting in the way that lead-tin yellow is the yellow of the seventeenth. And the consequences are now visible: research at the University of Antwerp and elsewhere, using synchrotron analysis on Van Gogh's paint, has shown that lead chromate reduces from Cr(VI) to Cr(III) under light, darkening to a brown-green, and that the pale sulphur-containing grades he favoured degrade fastest. Some of the sunflowers are measurably browner than when they were painted, and the process cannot be stopped.
In the studio
It is opaque, powerfully tinting, fast-drying and extremely easy to use — everything a painter wants from a colour, which is exactly the problem, since none of its defects are apparent in the studio. Beyond the light-induced darkening, it blackens in the presence of sulphur compounds, including atmospheric pollution, and it is seriously toxic, containing both lead and hexavalent chromium, a recognised carcinogen. Mixed with Prussian blue it was sold as chrome green, which inherits its instability.
Afterlife
Cadmium yellow displaced it for artists from the later nineteenth century, being stable and brighter if more expensive, and modern regulation of lead and hexavalent chromium has removed it from almost all use. Tubes labelled chrome yellow now contain azo or cadmium pigments. Its legacy is a conservation problem of the first order, distributed across a great many of the best-loved paintings of the nineteenth century.
Where it appears
Every era and artist in this atlas whose palette includes this pigment.