Pigment

A pigment is a solid that refuses to dissolve. Ground fine and suspended in a binder, it sits in the paint film as particles, scattering light back at you. That refusal is the whole difference between a pigment and a dye, and it decides which colours survive four centuries and which ones leave.

Where the word comes from

The word comes from Latin pigmentum, from pingere, to paint — the same root that gives us "picture" and, through a long detour, "paint" itself. But the distinction that matters is not linguistic. A dye dissolves and stains a fibre from within; a pigment stays whole and is glued to a surface by whatever it is mixed with: egg yolk, linseed oil, gum arabic, acrylic polymer. The colourmen who sold both knew that a dye could be turned into a pigment by precipitating it onto an inert powder. That hybrid has its own name, and its own page: the lake.

In the studio

Until the nineteenth century, pigment arrived as lumps and had to be ground by hand on a slab of porphyry or marble with a glass muller, worked into oil in circles until the grit disappeared under the heel of the hand. Grinding was not neutral. Particle size changes colour: ultramarine ground too fine turns pale and grey, so it was kept deliberately coarse and was a nuisance to brush out. Lead white takes an extremely fine grind and stays opaque. An apprentice who ground badly ruined expensive material, which is one reason the job sat at the bottom of the workshop and why the guilds regulated who could sell what.

Why it matters

Pigments were priced by weight like spices, and the price wrote itself into the paintings. Contracts from fifteenth-century Italy specify ultramarine by the ounce and by grade, because a patron who paid for lapis wanted lapis and not azurite in the Virgin's cloak. That is why the most expensive blue in Europe ended up reserved for the most important garment in the picture — not piety, procurement. Painters who could not afford it, or who were being underpaid, used smalt or indigo underneath and saved the good material for the top layer, where it would be seen.

Today

The pigment is now the forensic evidence. Conservators identify the particles in a paint sample and read them as a date stamp: Prussian blue does not exist before about 1706, zinc white before the 1780s, titanium white before the twentieth century. Find one in a painting that claims to be older and the painting is lying. Han van Meegeren, who sold fake Vermeers to Hermann Göring, was undone by exactly this — his "seventeenth-century" panels carried traces of cobalt blue and a phenol-formaldehyde resin he had used to make the paint harden like three-hundred-year-old oil.

Pigments used: Ultramarine · Lead white · Vermilion · Prussian blue