Cadmium red
The red that retired vermilion. Cadmium red arrived around 1910 with the same brilliance and opacity as mercury sulphide, none of the darkening, and none of the mercury, and within a generation it had taken over.
Origin
Chemically it is cadmium sulphide with selenium substituted for part of the sulphur, and the proportion of selenium determines the hue: more selenium gives a deeper, more purple red, less gives orange. The discovery was made in Germany around 1907 and commercial production began around 1910, delayed and then accelerated by the industrial chemistry of the period. Because the range from lemon yellow to deep maroon is one continuous chemical family, manufacturers can offer a complete warm spectrum of matched pigments with identical handling — which is itself a novelty in the history of the palette, where each colour had traditionally come from a different substance with different behaviour.
In art history
It appears in twelve eras of this atlas and is one of the defining colours of twentieth-century painting. Matisse used it, and the Fauve and Expressionist reliance on saturated unmixed colour depends on pigments like this being available. It is the red of Rothko's warm canvases, of Pop, and of most commercial and poster art. Its arrival can be traced through the database: eras before about 1910 use vermilion, eras after use cadmium, and a few sit on the boundary with both present as studios changed stock.
In the studio
Opaque, powerful, completely lightfast and stable in every mixture, including with the lead and copper pigments that older reds could not tolerate. It is slow-drying in oil, which is its one real inconvenience. It is not usable in fresco, being attacked by lime, and older grades containing free sulphur could cause problems, though modern manufacture is clean. Toxicologically it is the same story as cadmium yellow: cadmium compounds are toxic and carcinogenic, the sulphoselenide is very poorly soluble, and the practical hazard is inhalation of dry pigment rather than contact with paint.
Afterlife
It remains standard and remains expensive, and like cadmium yellow it faces periodic regulatory pressure in Europe over wastewater. The substitutes — naphthol and pyrrole reds — are close in hue and cheaper, and pyrrole in particular is genuinely excellent, opaque and lightfast, so the case for cadmium red is weaker than it was. Many painters have switched. Many have not, on the grounds that nothing else has quite the same density.
Where it appears
Every era and artist in this atlas whose palette includes this pigment.