A palette dug out of the ground
Every colour on a cave wall came out of the ground or out of the fire. Ochre is an earth stained by iron oxides: goethite makes it yellow, haematite makes it red. Heat the yellow kind to around 250-300 °C and the goethite gives up its water and becomes haematite, so a lump of yellow ochre left in the hearth comes out red. Analyses from several Palaeolithic sites suggest that people knew this and did it on purpose.
Black was charcoal, or manganese oxide. None of these earth pigments comes ready to use. They had to be found, crushed and ground, and the grind matters as much as it does with coffee: fine powder spreads smooth, coarse grains leave a rough, glittering surface.
Recipes, at least at Niaux
Some painters went further and mixed their paint. At Niaux, in the Pyrenees, Jean Clottes, Michel Menu and Philippe Walter identified four recipes in which the pigment was bulked out with talc, baryte, potassium feldspar or biotite. Biotite, a black mica, helps red paint spread and stops it cracking as it dries. Someone prepared all this before walking into the dark.
What made the colour stick is murkier. Water and the cave’s own damp were often enough, and analyses of Ice Age paintings in France rarely find binders such as fat or plant gum. Organic traces survive so badly, though, that their absence proves little.
Fingers, flint and the first airbrush
Fingers and pads of fur or moss give broad marks; a brush of hair or chewed fibre gives a line. For a soft mist of colour the painter blew pigment straight from the mouth, or through a hollow bone or reed, which is exactly how an airbrush works. Hold a hand flat against the rock while you do it and you get a hand stencil.
Does it really work? In 1990 the archaeologist Michel Lorblanchet tried. He copied the spotted horses of Pech Merle, about 25,000 years old, on the wall of a small cave, blowing and spitting the pigment and using his hand as a screen, and he got the same soft, dotted edges. That proves nothing about the originals. It does explain marks a brush can’t easily make.
Engravers had flint. A pointed flake scratches a fine line, repeated strokes deepen it, and a broad edge scrapes a whole patch paler. Some images are carved into the rock, others combine a scratched outline with colour inside, and where the wall was soft clay people simply drew with their fingers, leaving parallel grooves called finger flutings.
The wall itself was a tool. A cave wall is never flat, and painters made the most of it: a bulge becomes the belly of a bison, a ridge a horse’s neck, a hollow an eye. Spray over a swelling and you get volume without drawing a single edge.
A lamp from Lascaux
Every painted chamber needed light. Torches give a bright, jumpy flame and plenty of smoke. Stone lamps burning animal fat give a smaller, steadier one, roughly a candle’s worth, and the finest we have comes from Lascaux. André Glory found it in the Shaft, under one of the cave’s painted scenes: polished red sandstone, with burnt juniper still in the bowl and a sign engraved on the handle, of the same kind as the signs on the walls. It is now in the Musée national de Préhistoire at Les Eyzies.
Light also decides what you see. A low flame from the side brings out engraved lines and gives painted bodies depth. Hold it in front and they go flat.
Painting over painting
Plenty of panels were reworked. In the Salon Noir at Niaux most animals were first sketched in charcoal and then painted in manganese, and radiocarbon on the charcoal points to at least two campaigns, about 14,000 and 13,000 years ago. Elsewhere, new animals were simply drawn over old ones. For archaeologists those overlaps are precious, because they put a wall in order even when nothing on it can be dated.
In parts of northern Australia repainting is still how a site is looked after, so a single panel among the world’s oldest images on stone can hold the work of many generations.
Where to see the techniques
Niaux and Pech Merle still take small guided groups, usually by reservation, and the Lascaux lamp is on show at Les Eyzies. Numbers are kept low to protect the paint, so book through the official websites.
Sources
- J. Clottes, M. Menu and P. Walter, “La préparation des peintures magdaléniennes des cavernes ariégeoises”, Bulletin de la Société préhistorique française 87 (1990).
- “XRD study of the goethite-hematite transformation: application to the identification of heated prehistoric pigments” (HAL, Sorbonne Université).
- J. Clottes, Cave Art (Phaidon, 2008).
- M. Lorblanchet’s experiment at Pech Merle, reported in Discover, “Paleolithic Paint Job”.
- Ministère de la Culture, “Lascaux”: lighting and the red sandstone lamp (archeologie.culture.gouv.fr/lascaux).
- Bradshaw Foundation, “Niaux Cave”: paint recipes and the Salon Noir.
