Orpiment
A brilliant golden yellow that is pure arsenic sulphide — the only yellow before the eighteenth century with the saturation of gold, and one of the most poisonous substances ever put on a palette.
Origin
A natural mineral, found in volcanic and hot-spring deposits and mined in Asia Minor, Persia, Hungary and Macedonia. Its Latin name, auripigmentum, means golden pigment, and both its appearance and its association with gold made it central to alchemy — orpiment was one of the substances alchemists worked with most persistently in attempts at transmutation, on the reasonable-looking grounds that it already looked like the answer. A synthetic version, made by sublimation and known as king's yellow, appeared later and was purer and even more dangerous. Its orange-red sibling, realgar, occurs in the same deposits and was used the same way.
In art history
Orpiment is the great yellow of Persian and Indian manuscript painting, of Egyptian tomb decoration, of Byzantine work, and of European painting up to the seventeenth century wherever a strong yellow was needed and could be afforded. It appears in five eras here, weighted towards the non-European traditions, which reflects the historical reality: Persian miniature painting used it constantly and to spectacular effect. In Europe it was always somewhat restricted, partly by cost, partly by its incompatibilities, and partly because handling it was understood to be dangerous. Venetian painters used it; Cennini describes it and warns to beware of soiling your mouth with it.
In the studio
It is chemically hostile to half the palette. Being a sulphide, it blackens lead white and copper greens on contact, which rules out mixing it with the two most common pigment families in European painting and forces it into isolated passages. It is unstable in strong light, slowly degrading to a white arsenic oxide, and it is destroyed by lime, so it cannot be used in fresco. It is semi-opaque, has a distinctive slightly pearlescent quality from its flaky crystal structure, and it is acutely toxic by inhalation and ingestion — grinding it produced arsenic dust in an unventilated workshop.
Afterlife
It was gradually replaced from the eighteenth century by Naples yellow, chrome yellow and finally cadmium yellow, each brighter or safer or both. Orpiment is no longer sold as an artists' colour anywhere. It survives in conservation analysis, where its presence dates and locates a work, and in the odd historical footnote: it was used as a depilatory, a fly poison and a medicine, all of which worked in the sense that they had unmistakable effects.
Where it appears
Every era and artist in this atlas whose palette includes this pigment.