Scientists identify secret ingredient in da Vinci paintings

“Old Masters” such as Leonardo da Vinci, Sandro Botticelli and Rembrandt may have used proteins, especially egg yolk, in their oil paintings, according to a new study.
Trace quantities of protein residue have long been detected in classic oil paintings, though they were often ascribed to contamination. A new study published Tuesday in the journal Nature Communications found the inclusion was likely intentional — and sheds light on the technical knowledge of the Old Masters, the most skilled European painters of the 16th, 17th, or early 18th century, and the way they prepared their paints.
“There are very few written sources about this and no scientific work has been done before to investigate the subject in such depth,” said study author Ophélie Ranquet of the Institute of Mechanical Process Engineering and Mechanics at the Karlsruhe Institute of Technology in Germany, in a phone interview. “Our results show that even with a very small amount of egg yolk, you can achieve an amazing change of properties in the oil paint, demonstrating how it might have been beneficial for the artists.”
Simply adding some egg yolk to their works, it turns out, could have long-lasting effects that went beyond just aesthetics.
Scientists identify secret ingredient in da Vinci paintings