Medieval Paints and Pigments

Where did medieval manuscript illuminators get their colors?

Well, first thing to realize is that they weren't re-inventing the wheel: Romans had colored paints available to them. The Romans used the term minium to refer to pigment from ground cinnabar (brick-red mercury sulfide) or red lead (lead oxide). Some minerals that were dug up and ground included:

red ochre — iron oxide/hematite (rust color)
yellow ochre — silica and clay/iron oxyhydroxides (shades from cream to brown)
umber — iron and manganese oxides (from cream to brown)
lime white — dried lime/chalk (white)
green earth (Verona green) — celadonite/glauconite (green)
azurite — carbonate of copper (blue)
ultramarine — lapis lazuli (blue)

Pigments could also be made from plants. Red could be made from the root of the Eurasian madder plant. The Crozophora plant's seeds produced a violet-blue. Saffron gave yellow. Woad and indigo came from plants that carried the same name. Let's not forget insects, that could be crushed to give the bright-red carmine (from the cochineal or Dactylopius coccus scale insect). 

Preparation of paints was a careful process. The coloring was usually mixed gum arabic or with egg. Egg tempera (from the yolk) or egg glair (from the white) were ways to "fix" the pigment to the surface you were using. Because the egg tempera could crack, it was applied in paintings in thin layers.

Some colors were more special than others. Ultramarine (literally "beyond the sea"), the blue made from grinding lapis lazuli, came from Afghanistan and was very expensive to obtain. This brightest blue, however, was associated with the gown of Mary, the mother of Jesus, so it was greatly desired and worth the price.

Another questio0n regarding color in the Middle Ages comes to mind, however. How did they get the color into glass? That's for next time.