Appreciated today for its aesthetic qualities, color during the Middle Ages was also understood for its material, scientific, and medicinal properties. The manufacture of colored pigments and inks was part of the science of alchemy, the forerunner of modern chemistry. Concerned with the transformation of matter, alchemy was closely tied to artistic practice.
Theodas with the Book of Magic and the Devil, from Barlaam and Josaphat, 1469, Workshop of Diebold Lauber. The J. Paul Getty Museum
Medieval manuscript artists typically made paint from colored materials, ground into powder and mixed with a liquid binder.
Many of the most brilliant pigments didn’t come straight from nature, but were made through alchemy, an experimental practice that predates modern chemistry.
Beyond trying to change base metals into gold, the alchemists explored how materials interacted and transformed. Discovering paint colors was a practical outcome.
Alchemy embraced astrology, medicine, philosophy, and mysticism, and within those contexts, colors had specific meanings.
A brilliant red, vermilion, was associated with chemical change … and with alchemy itself. Producing vermilion involved combining two elements, sulfur and mercury, mixed and heated until a chemical reaction occurred. When ground into powder, vermilion turns deep red.
Many other vibrant pigments result from chemical transformations: Mosaic gold, produced by fusing tin and sulfur in the presence of mercury …
Verdigris, made by exposing copper to fumes of vinegar, wine, or even urine …
And lead white, made in a process similar to verdigris, but with lead.
Chemical transformation doesn’t just happen when a color is born. It can occur throughout the life of a pigment, even centuries later … and museum researchers study it.
The vivid colors of illuminations are often preserved because books are typically kept closed. But sometimes books are left open, and their pigments can fade from exposure to light.
Some colors darken from exposure to atmospheric conditions. Others corrode. Verdigris can actually destroy the parchment or paper it’s painted on.
Today, chemistry deepens our knowledge about paint colors: their identification and potential transformations.
Museums take preventative measures by controlling an artwork’s environment and exposure to light.
Sometimes an original color can be restored, as long as this is done carefully.
By analyzing the chemical nature of materials, scientists can visualize how a pigment may have looked when it was first created.
Chemistry also reveals the astonishing knowledge that medieval alchemists and painters brought to working with color.