A recent study indicates that renowned painters such as Leonardo da Vinci, Sandro Botticelli, and rembrandt likely incorporated proteins, especially egg yolk, into their oil paintings.

While trace amounts of protein residue have been detected in classic oil paintings for some time, they were often dismissed as contamination. Though, a new study published Tuesday in Nature Communications suggests that this inclusion was deliberate. The findings shed light on the technical expertise of the Old Masters-highly skilled European painters from the 16th to early 18th centuries-and their paint preparation methods.

“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.”

The addition of egg yolk appears to have enhanced the qualities of their works.

New Understanding of the classics

“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…”

The study also examined “The Lamentation Over the Dead Christ” by Botticelli, which is displayed at the Alte Pinakothek. While primarily tempera, oil paint was used in the background and some minor elements.

“We knew that some parts of the paintings show brushstrokes that are typical for what we call an oil painting, and yet we detected the presence of proteins,” Ranquet said. “Because it’s a very small quantity and they are arduous to detect, this might be dismissed as contamination: In workshops, artists used many different things, and maybe the eggs were just from the tempera.”

However, the study suggests that the presence of proteins might indicate intentional use, given the desirable effects of adding egg yolk to oil paint. Ranquet hopes these initial findings will spark further investigation into this relatively unexplored area.

Maria Perla Colombini, a professor of analytical chemistry at the University of Pisa in Italy, who was not involved in the study, concurred. “This exciting paper provides a new scenario for the understanding of old painting techniques,” she said in an email.

“The research group, reporting results from molecular level up to a macroscopic scale, contributes to a new knowledge in the use of egg yolk and oil binders. They are not more looking at simply identifying the materials used by old Masters but explain how they could produce fantastic and glittering effects by employing and mixing the few available natural materials. They try to discover the secrets of old recipes of which little or nothing is written,” she added.

“This new knowledge contributes not only to a better conservation and preservation of artworks but also to a better comprehension of art history.”

Top Image: The “Mona Lisa” by leonardo da vinci