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“Old Masters” like Leonardo da Vinci, Sandra Botticelli and Rembrandt may have used proteins, especially egg yolk, in their oil paintings, according to a new study.
Traces 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 probably 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 paintings.
“There are very few written sources on this and no scientific work has been done before to investigate the topic in such depth,” said study author Ophélie Ranquet of the Institute of Mechanical Process Engineering and Mechanics at the Karlsruhe Institute of Technology in Germany, in a telephone interview. “Our results show that even with a very small amount of egg yolk, a surprising change in properties can be achieved in oil paint, demonstrating how it could have been beneficial for artists.”
It turns out that simply adding a little egg yolk to your works could have lasting effects that went beyond mere aesthetics.
Compared with the means formulated by the ancient Egyptians called Oil tempera paint, which combines egg yolk with powdered pigments and water, creates more intense colors, allows for very smooth color transitions, and dries much less quickly, so it can be used for several days after preparation. However, oil paint, which uses linseed or safflower oil instead of water, also has disadvantages, such as being more susceptible to color darkening and damage caused by light exposure.
Because making paint was an artisanal and experimental process, the Old Masters may have added egg yolk, a familiar ingredient, to the new type of paint, which first appeared in the 7th century in Central Asia before spreading to the north Europe. in the Middle Ages and in Italy during the Renaissance. In the study, researchers recreated the paint-making process 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 adjust the properties of these paints drastically,” said Ranquet, “for example, by showing aging differently: the paint takes longer to oxidize, due to the antioxidants it contains.” . in the yolk.”
Chemical reactions between the oil, pigment and yolk proteins directly affect the behavior and viscosity of the paint. “For example, white lead pigment is quite sensitive to humidity, but if you cover it with a layer of protein, it becomes much more resistant, which makes the paint quite easy to apply,” Ranquet said.
“On the other hand, if you want something more rigid without having to add a lot of pigment, with a little egg yolk you can create a painting with a lot of impasto,” he adds, referring to a painting technique in which the paint is arranged in a stroke thick enough so that the brush strokes are still visible. According to Ranquet, 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.
Direct evidence of the egg yolk effect in oil painting, or lack thereof, can be seen in Leonardo da Vinci's “Madonna of the Carnation.” one of the paintings observed during the study. Currently on display at the Alte Pinakothek in Munich, Germany, the work shows obvious wrinkles on the faces of Mary and the child.
“Oil paint starts drying from the surface down, which is why it wrinkles,” Ranquet said.
One of the causes of wrinkles can be an insufficient amount of pigments in the paint, and the study has shown that this effect could be avoided by adding egg yolk: “It's quite surprising, because in the paint you have the same amount of pigment, but the presence of the egg yolk changes everything.”
Because wrinkles occur within days, it is likely that Leonardo and others The old masters may have noticed this particular effect, as well as the additional beneficial properties of egg yolk in oil paint, including moisture resistance. The “Madonna of the Carnation” is one of Leonardo's earliest paintings, created at a time when he may still have been trying to master the then-recently popular medium of oil painting.
New understanding of the classics.
Another painting observed during the study was “The Lamentation over the Dead Christ” by Botticelli, also exhibited in the Alte Pinakothek. The work is done mostly with tempera, but oil paint has been used for the background and some secondary elements.
“We knew that some parts of the paintings show brush strokes typical of what we call oil painting, and yet we detected the presence of proteins,” Ranquet said. “As this is a very small amount and they are difficult to detect, this could be considered contamination: in the workshops, artists used many different things, and perhaps the eggs simply came from tempera.”
However, because adding Egg yolk had such desirable effects in oil paint that the presence of protein in the work could be an indication of deliberate use. the study suggests. Ranquet hopes these preliminary findings can draw more curiosity to this understudied topic.
Maria Perla Colombini, a professor of analytical chemistry at the University of Pisa in Italy, who was not involved in the study, agreed. “This interesting article provides a new setting for understanding ancient painting techniques,” she said in an email.
“The research group, by presenting results from the molecular level to the macroscopic scale, contributes to new knowledge in the use of egg yolk and oil binders. They no longer simply identify the materials used by the old masters, but explain how they could produce wonderful and brilliant effects using and mixing the few natural materials available. “They try to discover the secrets of ancient recipes about which little or nothing is written,” he added.
“This new knowledge contributes not only to better conservation and preservation of works of art, but also to a better understanding of art history.”
Cover image: The “Mona Lisa” by Leonardo Da Vinci
