The great Renaissance masters added egg yolk to their oil paints in order to protect their masterpieces against yellowing and humidity and to prevent the formation of cracks during drying, according to research published in Nature Communications and led by Italian scientists.

"So far, scientific investigations of paintings have mostly been aimed at identifying the materials used by painters, but this is not enough to understand the reasons behind the artistic practice," Ilaria Bonaduce, an associate professor at the Department of Chemistry and Industrial Chemistry at the University of Pisa, told ANSA.