Viridian

#1F7A5CFormula Cr₂O₃·2H₂OEarliest recorded use 1838

13 eras28 artists33 colors

The green that solved the problem. Viridian is cool, transparent, deep, completely permanent and entirely non-toxic, and its arrival ended a two-thousand-year search for a green that was neither weak, nor poisonous, nor doomed to turn brown.

Origin

A hydrated chromium oxide, first prepared in Paris by Pannetier and Binet around 1838 — who kept the process secret and sold it at a high price — and patented in a reproducible form by Charles-Ernest Guignet in 1859, after which it became cheap and universal. It is often called Guignet's green or vert émeraude in French, which causes lasting confusion with the arsenical emerald green it replaced: in French, vert émeraude means viridian, and the two pigments are chemically unrelated and morally opposite. Its dull, opaque, anhydrous sibling, chromium oxide green, is a different pigment with a different character.

In art history

Viridian arrives in the middle of Impressionism and is taken up immediately, appearing in eleven eras of this atlas — the most-used green in the entire database. Cézanne built landscape with it. Monet, Renoir, Seurat and Van Gogh all used it, and it is the green underlying a great deal of what we think of as the Impressionist palette, since mixed with cadmium yellow it gives the full range of foliage and mixed with white it gives the cool blue-greens of water. Its transparency made it valuable to the Neo-Impressionists and to everyone glazing afterwards. It remains standard today, which after two centuries of green pigments failing or poisoning people is a considerable achievement.

In the studio

It is transparent, deeply saturated in mass and surprisingly cool — bluer than most painters expect, which is why it is often mixed rather than used straight. It has moderate tinting strength, dries at an average rate, and is absolutely lightfast, alkali-resistant, acid-resistant and stable with every other pigment, including the sulphur colours that destroyed every copper green before it. It works in oil, watercolour, tempera, acrylic and fresco without qualification. Its texture in watercolour is distinctive, granulating into a slightly crystalline sparkle.

Afterlife

Still made, still standard, still on most palettes, though phthalocyanine green — introduced in 1938, far stronger and cheaper — has taken over much of the commercial and industrial work. Phthalo is more intense but harder to control; viridian's comparative gentleness keeps it in the artists' range. Many tubes sold as viridian hue are phthalo and white, which is a different material behaving differently.