Emerald green
A copper arsenite of extraordinary brilliance, sold under a dozen cheerful names, used in wallpaper, dresses, sweets and children's toys, and poisonous enough that it was simultaneously marketed as an insecticide. Emerald green is the most notorious pigment ever manufactured.
Origin
Developed in Schweinfurt, Bavaria, in 1814 as an improvement on Scheele's green, an earlier and duller copper arsenite from 1775, it was made by combining verdigris with arsenic trioxide. The result was a green of a purity nothing had previously approached, cheap to make and instantly popular. It was sold as Schweinfurt green, Paris green, Vienna green, Veronese green and emerald green, and the same product, unmodified, was sold to farmers as Paris green for killing potato beetles and to municipalities for killing mosquito larvae. Nobody found this contradictory for most of a century.
In art history
Its nineteenth-century ubiquity is hard to overstate. It coloured the wallpaper of ordinary houses across Europe, and in damp rooms moulds acting on the arsenic released trimethylarsine gas, producing a slow poisoning whose symptoms were recorded repeatedly without the cause being identified. Green ball gowns and artificial flower wreaths dosed the women who wore them and the girls who made them; a well-documented London case in 1861 concerned a nineteen-year-old artificial-florist who died of arsenic poisoning after dusting leaves with the powder. The theory that Napoleon was killed by the green wallpaper of his room on Saint Helena is a persistent, unproven, and entirely plausible version of the same story. Painters used it too — it is present in Impressionist and Post-Impressionist work, and Van Gogh used it, though the popular claim that it drove him mad is speculation.
In the studio
Chemically it is a copper pigment and behaves like one: it blackens on contact with sulphur, so it cannot be mixed with cadmium or ultramarine, which limited it severely in practice. It is not reliably lightfast in all binders, tends to darken over time in oil, and is aggressively toxic in handling as well as ingestion. Against all of that it offered a green of a saturation that painters had waited centuries for, and for about seventy years they accepted the terms.
Afterlife
Viridian, stable and non-toxic, displaced it for artists from the 1860s, and legislation gradually removed it from consumer goods, though its agricultural use as an insecticide continued well into the twentieth century. It appears in five eras of this atlas, all of them nineteenth-century. It is no longer manufactured as an artists' colour; modern tubes labelled emerald green contain phthalocyanine mixtures, and the arsenic version survives mainly in museum storerooms, where it is handled with gloves.
Where it appears
Every era and artist in this atlas whose palette includes this pigment.