Modern digital artists have millions of colors available, and modern painters have almost as many synthetic paints at their fingertips. But in the past, painters used pigments made from chemicals the natural world offered -and many of those are no longer used because they were dangerous, expensive, or made from sources no longer available -like endangered species. For example, the bygone pigment called Mummy Brown:
The pigment, a favored shade of the Pre-Raphaelites, was first made with Egyptian mummies, both cat and human, that were ground up and mixed with white pitch and myrrh. It had a great fleshy color, but due to the actual fleshy components it would crack over time. Martin Drölling, who painted the work shown above, reportedly used the mummies of French kings dug up from Saint-Denis in Paris. According to a 1964 Time story, the Mummy Brown pigment didn’t last due to a shortage of its name defining ingredient.
You might be surprised at what's on those masterpieces in museums! Allison Meier at Hyperallergic tells the stories of some of those pigments of yore, in two posts because the first was so popular.
Link to part one.
Link to part two. -via Metafilter