As Kassia St. Clair writes in her book, The Secret Lives of Color, lead white has been manufactured since at least 2300 B.C.E. and its production has changed very little since Pliny the Elder shared his methods in the first century C.E. Lead was first extracted from rocks, then placed into one side of a two-holed clay pot. In the other vestibule went vinegar. And the receptacles were surrounded by poop. "Fumes from the vinegar reacted with the lead to form lead acetate; as the dung fermented it let off CO2, which, in turn, reacted with the acetate, turning it into carbonate," St. Clair writes. "After a month some poor soul was sent into the stench to fetch the pieces of lead, by now covered in a puff-pastry-like layer of white lead carbonate, which was ready to be powdered, formed into patties, and sold." The process was dangerous, as was the pigment itself if ingested. But artists liked lead white's durability and price point, so it remained on artist's palettes well into the 20th century.