An Old Master’s secret ingredient? Egg yolk, new study suggests

“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.“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.