Egg yolk has been revealed as the secret to preserving Renaissance masterpieces for over 500 years. According to a study by Professor Norbert Willenbacher and his research team from the Karlsruhe Institute of Technology in Germany, published in the journal Nature Communications on the 29th of March, the use of egg yolk in oil painting helped to prevent problems such as wrinkles and discoloration.
Egg yolk has been widely used as a binder from prehistoric times to the Middle Ages. However, with the development of oil painting in Europe from the 15th century, it was eventually replaced by oil as the binder. Nonetheless, egg yolk is still found in the works of Renaissance masters such as Sandro Botticelli and Leonardo da Vinci.
For instance, in Botticelli’s 1490 work “Lamentation over the Dead Christ,” egg yolk can be seen in the paint layer on the face of Christ (on the right) and on the left foot of St. John (on the left), which differs from the surrounding oil paint.
To understand the use of egg yolk in oil painting, the research team conducted experiments by adding a few drops of egg yolk to one side of oil paint mixed with linseed oil, and adding a mixture of egg yolk solution and pigment to the other side, comparing them both.
The study found that the more egg yolk was added, the thicker the paint layer became, making it more suitable for the impasto technique, which creates a three-dimensional effect by applying thick layers of paint. Professor Willenbacher explained that “if the paint layer becomes thicker, it can prevent cracks and wrinkles from appearing during the drying process.”
Egg yolk also formed a protein layer around the pigment, inhibiting moisture absorption and protecting the painting from damage in humid weather. Additionally, it acted as an antioxidant that prevented the yellowing of oil paint during the drying process by reacting with oxygen and oil.
The study not only sheds light on the understanding of masterpieces but also provides insight into preserving artwork for future generations.