Famous painters like Leonardo da Vinci, Sandro Botticelli, and other Renaissance masters may have experimented with mixing egg yolk into their oil paint to help the paintings withstand humidity and to prevent wrinkling and yellowing, scientists have found.

Research into the painting habits of the master painters "might improve the preservation of invaluable artworks," a study published by Nature Communication said.

While protein residue was previously detected in the masterpieces, the study shows that including the eggs were likely deliberate.

In the study, experts found that adding eggs to oil paintings "acts as an antioxidant, slowing down the onset of curing." In other words, this combination helps to stop the paint from degrading.

"There are very few written sources about this, and no scientific work has been done before to investigate the subject in such depth," study author Ophélie Ranquet of the Institute of Mechanical Process Engineering and Mechanics at the Karlsruhe Institute of Technology in Germany, told CNN.

"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."

In examining the effects of using egg yolk proteins in the oil, the scientists found that the egg proteins suppressed the water absorbed in the paint in humid environments.

While paintings dried, they also helped prevent yellowing and wrinkling – "a problem even Leonardo da Vinci encountered," the study found.

The artists "gave us the opportunity to admire their masterpieces still today," the study said.

This article was originally published by Business Insider.

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