Verdigris
The most brilliant green available before the eighteenth century, and the most treacherous. Verdigris is corroded copper — literally rust, deliberately grown — and it is beautiful, transparent, intense, and capable of eating through the paper it is painted on.
Origin
The recipe is old and domestic: stack copper sheets in a sealed pot with vinegar, or with grape skins and pomace left over from winemaking, and wait. Over weeks a blue-green crust of copper acetate forms on the metal, which is scraped off and ground. Montpellier in southern France was the centre of production for centuries, the work done largely by women in household cellars using the residue of the wine harvest, and the town supplied most of Europe. The colour varies with the method — bluer with more acetate, greener with less — and the material is deliquescent, absorbing moisture from the air, so it had to be kept sealed.
In art history
Verdigris is the green of medieval manuscripts, of fifteenth and sixteenth-century panel painting, and of any period that needed a green with real saturation, since the alternatives were green earth, which is weak, and mixtures of blue and yellow, which are dull. Painters used it as a glaze, most spectacularly in the transparent green draperies and landscapes of Northern Renaissance painting, and dissolved it in resin to make copper resinate, a deep emerald glaze that is one of the most beautiful and least stable materials in the history of the medium. It appears in four eras here, all early, and its disappearance from the record after the eighteenth century is a straightforward story of a better product arriving.
In the studio
The problems are numerous and serious. Verdigris is a copper salt and chemically aggressive: in watercolour and manuscript illumination it attacks the cellulose of the paper or parchment beneath it, and there are medieval manuscripts where the green passages have corroded clean through, leaving green-edged holes in the page. It blackens on contact with sulphur pigments, so it cannot be mixed with vermilion, orpiment or ultramarine. In oil, copper resinate glazes have very often browned, turning what were brilliant green landscapes into brown ones — the muddy foliage in a great deal of sixteenth-century painting is not the artist's taste but a chemical failure. It is also toxic. Painters knew most of this and used it anyway, because nothing else was that green.
Afterlife
It was displaced first by emerald green in the 1810s and then decisively by viridian, and it has no place on a modern palette. It survives in conservation science as a diagnostic marker and in the visible world as the patina of copper roofs and bronze statues, which is the same compound family forming by the same process, just more slowly and without anyone collecting it.
Where it appears
Every era and artist in this atlas whose palette includes this pigment.