Beyond the earth pigments lies a more complex tradition of colour-making that requires chemical transformation of metals and minerals. These are the pigments that gave the medieval palette its most remarkable blues, greens, and whites — and they are the colours that require the most knowledge, patience, and care to produce at the time when alchemy was on the cusp of transforming into chemistry
Verditer, one of England's distinctive blue-green pigments, is produced when copper reacts with nitric acid in the presence of chalk or limestone. Historically, English verditer was a by-product of silver refining: when silver was extracted from argentiferous copper ores using nitric acid (aqua fortis), to discover more about this world