Orpiment was one of the very few bright, clear yellow pigments available to artists until the 19th century and was a regular ingredient in the Middle Ages for paint- ing and especially for writing as an imitation of gold.

Its very name recalls this connection: auripigmentum, ‘colour of gold’. In the ancient world it was believed that the super cial resemblance had deeper alchemical roots: that orpiment contained gold itself. It was said that the Roman emperor Caligula was able to extract gold from the mineral.

Known to the Greeks as arsenikon which is related to the Persian zarnikh, based on the word zar, the Persian for gold.

Orpiment is a sul de of arsenic, found in nature as a rock or a crystal and is highly toxic.

Aware of its poisonous nature the Romans called it arrhenicum, from which the word arsenic is derived and the Romans used slave labour to mine it. For the unlucky slaves this was, in essence, a death sentence.

A manufactured version was available from the 17th century and was known as King’s Yellow. It was very popular with Dutch masters, sometimes mixed with blue to make their landscapes green. Yet not only were the fumes poisonous, it also apparently smelled horrid. To make things worse it reacted with lead-based pig- ments and caused them to turn black.