Unheard of before/ Scientists identify secret ingredient in Leonardo da Vinci's paintings

"Old Masters" such as Leonardo da Vinci, Sandro Botticelli and Rembrandt may have used proteins, specifically egg yolk, in their oil paintings, according to a new study.

Trace amounts of protein residues have long been detected in classical oil paintings, although they were often attributed to contamination. A new study published Tuesday in the journal Nature Communications found that the inclusion was likely intentional and sheds light on the technical knowledge of the Old Masters, the most skilled European painters of the 16th, 17th or early 18th centuries. -, and the way they prepared their paints.

"There are very few written sources about this and no scientific work has been done before to investigate this topic in such great depth," said study author Ophélie Ranquet of the Institute of Mechanical Process Engineering and Mechanics at the Institute of Technology in Karlsruhe, Germany in a telephone interview. "Our results show that even with a very small amount of egg yolk, you can achieve an amazing change in the properties of oil paint, demonstrating how useful it can be for artists."

Simply adding a little egg yolk to their works can have long-term effects that go beyond mere aesthetics.

Eggs vs. Oil

Compared to the medium formulated by the ancient Egyptians called tempera – which combines egg yolk with powdered pigments and water – oil paint creates more intense colors, allows for very smooth color transitions and dries slightly faster. However, oil paint, which uses linseed oil instead of water, also has drawbacks, including being more susceptible to color fading and damage caused by exposure to light.

Because paint-making was an artisanal and experimental process, it is possible that the Old Masters may have added egg yolk, a familiar ingredient, to the newer type of paint that first appeared. first seen in the seventh century in Central Asia before spreading to Northern Europe in the Middle Ages and Italy during the Renaissance.

Në studim, studiuesit rikrijuan procesin e bërjes së bojës duke përdorur katër përbërës – të verdhën e vezës, ujë të distiluar, vaj liri dhe pigment – për të përzier dy ngjyra historikisht të njohura dhe domethënëse, të bardhën e plumbit dhe blunë ultramarine.

“Shtimi i të verdhës së vezës është i dobishëm sepse mund të rregullojë vetitë e këtyre bojërave në një mënyrë drastike,” tha Ranquet, “Për shembull duke e treguar plakjen ndryshe: Duhet një kohë më e gjatë që boja të oksidohet, për shkak të antioksidantëve që përmban në të verdhën e verdhë.”

The chemical reactions between the oil, pigment and proteins in the egg yolk directly affect the behavior and viscosity of the paint. "For example, white lead pigment is quite sensitive to moisture, but if you coat it with a protein layer, it makes it much more resistant to it, making the paint quite easy to apply," Ranquet said. .