Orpiment (arsenic trisulfide) was the most brilliant yellow available before the 19th century — used from ancient Egypt through the Renaissance. Like its companion realgar, it was extremely toxic and unstable in mixtures.

Orpiment yellow carries dangerous beauty — it is the yellow of extreme brightness achieved through extreme risk. In art history it represents the pre-modern calculus where colour and poison were inseparable.

Used in Egyptian New Kingdom paintings and Persian and Mughal manuscripts, where its brilliant yellow-gold creates the impression of actual gold. The word "orpiment" comes from Latin auripigmentum (gold pigment). Caravaggio and Rembrandt both used it carefully, knowing its incompatibilities.