Ultramarine

#2A4A8AFormula Na₈₋₁₀Al₆Si₆O₂₄S₂₋₄Earliest recorded use c. 600 CE

19 eras30 artists35 colors

For eight centuries ultramarine was the most expensive substance a painter could put on a panel — worth more, by weight, than gold. Its name means "beyond the sea", the direction the ships carrying it came from.

Origin

The pigment is ground lazurite, the blue mineral inside lapis lazuli. Until the nineteenth century, effectively all of it came from a single source: the Sar-e-Sang mines in the Badakhshan valley of what is now Afghanistan, worked continuously for more than six thousand years. The raw stone is not blue enough on its own — crush lapis and you get a disappointing grey. The colour had to be extracted, and the method, described by Cennino Cennini around 1400, was punishing: the powdered stone was kneaded for days inside a dough of pine resin, gum mastic and beeswax, submerged in lye, and the pure blue particles were coaxed out in successive washes. The first wash gave the deepest blue. The last gave a pale grey-blue called ultramarine ash, which painters used for skies and underlayers because they could not bear to waste it.

In art history

The cost shaped the pictures themselves. Renaissance contracts specified ultramarine by weight and by grade, in the same clause as the gold leaf: a patron commissioning an altarpiece was buying a quantity of blue as much as an image. This is why the Virgin's mantle is blue — the most expensive pigment was assigned to the most important figure, a hierarchy of cost made visible. Painters who could afford it lavishly announced the fact. Vermeer used natural ultramarine with a recklessness that helps explain why he died in debt, and not only in the obvious places: he laid it into the shadows of a white wall, into the ground layers beneath flesh, where no viewer would ever consciously see it. Titian built Venetian skies from it. Others economised, underpainting in cheap azurite and reserving a single thin ultramarine glaze for the surface.

In the studio

Ultramarine is chemically stable in oil but temperamental in company. It resists light almost perfectly — a five-hundred-year-old ultramarine mantle is often the least faded thing in the painting — yet it is vulnerable to acid, which strips the blue out and leaves a grey haze known as ultramarine sickness. It has poor covering power, so it was applied in glazes over a light ground rather than mixed heavily with white, which greys it. In tempera it stays vivid; in fresco the lime attacks it, which is why medieval wall painters applied it a secco, on top of dry plaster, and why so much of it has flaked away from church walls while the surrounding fresco survives intact.

Afterlife

In 1824 the Société d'Encouragement pour l'Industrie Nationale offered six thousand francs to anyone who could make ultramarine synthetically. Jean-Baptiste Guimet claimed the prize in 1828, and within a decade the price of blue collapsed by a factor of several thousand. French ultramarine is chemically near-identical to the mineral, though its particles are smaller and more uniform, which makes it slightly flatter and more purple than the natural stone — the difference is visible if you set a Vermeer beside an Impressionist sky. The cheap blue arrived precisely when painters began working outdoors at speed, and it is not a coincidence that nineteenth-century painting turned blue. Natural ultramarine is still sold to conservators and a handful of painters, at prices that make the point.