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“Old Masters” such as Leonardo da Vinci, Sandro Botticelli’s and Rembrandt’s oil paintings may contain proteins, particularly egg yolk. A new study.

For years, oil paintings of classics have contained small quantities of proteins. These residues are often mistakenly attributed to contamination. The presence of protein residues in classic oil paintings has long been detected, though they were often attributed to contamination. new study published Tuesday In the Journal Nature Communications found the inclusion was likely intentional — and sheds light on the technical knowledge of the Old Master painters, European master painters, from the 16th-17th or early 18th Century, and their techniques for preparing paint.

“There are very few written sources about this and no scientific work has been done before to investigate the subject in such depth,” You can also read about the importance of this in our article study author Ophélie Ranquet of the Institute of Mechanical Process Engineering and Mechanics at the Karlsruhe Institute of Technology in Germany, in a phone interview. “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.”

The effects of adding egg yolk to artworks go beyond aesthetics.

Comparable to the Egyptian medium 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 far less quickly, so it can be used for several days after its preparation. Oil paints that use linseed oil or safflower instead of water have some drawbacks. They are more susceptible to darkening colors and to damage from exposure to sunlight.

It is possible, because the process of making paint was an experimental and artisanal one, that some colors may have been contaminated. Old The newer paint type, first seen in Central Asia in the 7th century, may have been enriched with egg yolk by masters. spreading to Northern Europe In the Middle Ages, and Italy in Renaissance Italy. The Renaissance was a time of great change in Europe. study, the researchers recreated the process of paint-making by using four ingredients — egg yolk, distilled water, linseed oil and pigment — to mix two historically popular and significant colors, lead white and ultramarine blue.

“The addition of egg yolk is beneficial because it can tune the properties of these paints in a drastic way,” Ranquet said, “For example by showing aging differently: It takes a longer time for the paint to oxidize, because of the antioxidants contained in the yolk.”

The chemical reactions between the oil, the pigment and the proteins in the yolk directly affect the paint’s behavior and viscosity. “For example, the lead white pigment is quite sensitive to humidity, but if you coat it with a protein layer, it makes it a lot more resistant to it, making the paint quite easy to apply,” Ranquet said.

“On the other hand, if you wanted something stiffer without having to add a lot of pigment, with a bit of egg yolk you can create a high impasto paint,” She added that this technique is used to paint in such a way as the strokes of the brush are visible. Using less pigment would have been desirable centuries ago, when certain pigments — such as lapis lazuli, which was used to make ultramarine blue — were more expensive than gold, according to Ranquet.

A direct evidence of the effect of egg yolk in oil paint, or lack thereof, can be seen in Leonardo da Vinci’s “Madonna of the Carnation,” One of the paintings that was observed during the study. The work is currently on display in Munich at the Alte Pinakothek. It shows visible wrinkles on Mary’s face and that of the child.

“Oil paint starts to dry from the surface down, which is why it wrinkles,” Ranquet said.

The paint may wrinkle due to a lack of pigments. study This effect can be prevented by adding egg yolk. “That’s quite amazing because you have the same quantity of pigment in your paint, but the presence of the egg yolk changes everything.”

Because wrinkling occurs within days, it’s likely that Leonardo and other Old The masters would have noticed this effect as well as the additional benefits that oil paints can offer, like resistance to humidity, and egg yolk. This is the “Madonna of Carnation” is one of Leonardo’s earliest paintings, created at a time when he might have been still trying to master the then newly popular medium of oil paint.

A second painting was observed at the study It is a good idea to use “The Lamentation Over the Dead Christ,” Botticelli’s work is on view at the Alte Pinakothek. Most of the work was done with tempera paint, although oil paint is used to cover some background elements and secondary details.

“We knew that some parts of the paintings show brushstrokes that are typical for what we call an oil painting, and yet we detected the presence of proteins,” Ranquet said. “Because it’s a very small quantity and they are difficult to detect, this might be dismissed as contamination: In workshops, artists used many different things, and maybe the eggs were just from the tempera.”

Because adding If the oil paint was painted with egg yolk, it would have been a good idea to use the protein instead. You can also find out more about the following: study suggested. Ranquet hopes these preliminary findings will attract greater interest to this topic.

Maria Perla Colombini was a professor of Analytical Chemistry at the University of Pisa (Italy), who wasn’t involved in the study, agreed. “This exciting paper provides a new scenario for the understanding of old painting techniques,” She said via email.

“The research group, reporting results from molecular level up to a macroscopic scale, contributes to a new knowledge in the use of egg yolk and oil binders. They are not more looking at simply identifying the materials used by Old Masters but explain how they could produce wonderful and glittering effects by employing and mixing the few available natural materials. They try to discover the secrets of old recipes of which little or nothing is written,” She added.

“This new knowledge contributes not only to a better conservation and preservation of artworks but also to a better comprehension of art history.”

Image: Top of the page “Mona Lisa” Leonardo Da Vinci