Painting conditioned by chemistry: the case of Egyptian and ultramarine blue pigments

Abstract Painting, from its beginnings over 30,000 years ago, has been conditioned by the availability of pigments, whether mineral or synthesised by ingenious craftsmen and manufacturers. While the yellow (yellow ochre) and red (red ochre) colours from surface minerals and black from charcoal used in cave paintings (30,000–15,000 BC) were readily available, the blue of sky and water was the last colour to appear in painting. This lecture text considers the two blue pigments that dominated painting from Ancient Egypt to the seventeenth century, before the advent of industrial pigments: (1) Egyptian blue, a synthetic product, and (2) ultramarine blue, an expensive imported mineral pigment that replaced Egyptian blue during the Renaissance, the recipe for which was lost with the fall of the Roman Empire. For both pigments, the crystal structure that houses and protects the chromophore is discussed in detail, as are the nature of the chromophore, the mechanism of colour formation, and the progress of synthesis from ancient kilns to industrial production and to student laboratory exercises. The impact of the availability and cost of the two pigments on the development of painting over time is illustrated chronologically through paintings from Ancient Egypt to Impressionism. Graphical abstract