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Renaissance artists like Leonardo da Vinci, Sandro Botticelli, and Rembrandt may have incorporated proteins, particularly egg yolk, into their oil paintings, as indicated by a recent investigation.
Even though trace amounts of protein residues have been commonly found in traditional oil paintings, they were typically thought to be accidental. However, a recent study released on Tuesday in the journal Nature Communications suggests that the inclusion was likely deliberate, offering insights into the technical expertise of the Old Masters, the most talented European painters of the time, and how they prepared their paints.
Ophélie Ranquet from the Karlsruhe Institute of Technology in Germany, who led the study, stated, “There is very limited written information on this topic, and no prior scientific research has been conducted to this extent.” Ranquet added, “Our findings indicate that even a small amount of egg yolk can significantly alter the properties of the oil paint, showcasing its potential benefits for artists.”
The addition of egg yolk to their masterpieces could have lasting effects beyond just visual appeal.
Oil paint, in contrast to the ancient Egyptian medium known as tempera, offers more vibrant colors, seamless color transitions, and extended working time. Nonetheless, oil paint, which incorporates linseed or safflower oil instead of water, has drawbacks such as increased vulnerability to color deterioration and light exposure damage.
As paint production was largely experimental, it is plausible that the Old Masters added egg yolk, a common ingredient, to the new type of paint that emerged in Central Asia in the seventh century before spreading to Northern Europe in the Middle Ages and Italy during the Renaissance. In their research, the scientists replicated the paint-making process using egg yolk, distilled water, linseed oil, and pigments to create two historically significant colors, lead white and ultramarine blue.
“The integration of egg yolk can yield significant changes in the attributes of these paints,” mentioned Ranquet, “For instance, it affects aging differently, extending the time it takes for the paint to oxidize due to the antioxidants present in the yolk.”
The chemical interactions between the oil, pigment, and proteins in the yolk directly impact the behavior and thickness of the paint. “For example, when a protein layer is applied to the lead white pigment, it becomes more resistant to humidity, making it easier to apply,” explained Ranquet.
“Conversely, if a sturdier texture is desired without using excessive pigment, a small amount of egg yolk can result in a highly textured paint,” she added, referring to impasto, where paint is applied in thick strokes, leaving brush marks visible. Centuries ago, using fewer pigments was advantageous, especially since certain costly pigments like lapis lazuli were more expensive than gold, noted Ranquet.
The impact of egg yolk on oil paint is evident in Leonardo da Vinci’s painting “Madonna of the Carnation”, displayed at the Alte Pinakothek in Munich, Germany, where noticeable wrinkling is observed on the faces of figures like Mary and the child.
The drying process of oil paint, starting from the surface down, can lead to wrinkling, explains Ranquet.
The study indicates that a lack of pigments in the paint might cause wrinkling, but adding egg yolk can prevent this effect: “The presence of egg yolk can alter the outcome even with the same amount of pigment in the paint.”
The ability of egg yolk to prevent wrinkling and offer resistance to humidity suggests that Old Masters like Leonardo da Vinci may have recognized these benefits in their early works, like the “Madonna of Carnation,” as they experimented with oil paint.
New insights into classical art
The study also examined Botticelli’s “The Lamentation Over the Dead Christ” at the Alte Pinakothek, which features a mix of tempera and oil paint in different sections of the artwork.
Although some parts of paintings like Botticelli’s show characteristics of oil paint, the presence of proteins detected suggests a deliberate use of egg yolk, rather than mere contamination: “The intentional use of proteins could be an indication of egg yolk in the paint,” according to the study.
The study proposes that the beneficial effects of egg yolk in oil paint could lead to a better understanding of historical painting techniques, sparking more interest in this less-explored area.
Analytical chemistry professor Maria Perla Colombini from the University of Pisa, who was not part of the study, concurred, stating that this research brings a fresh perspective to traditional painting methods.
Colombini praised the study’s findings for shedding light on the use of egg yolk and natural materials in creating stunning effects in art, surpassing the mere identification of materials used by Old Masters to exploring the secrets behind their innovative techniques.
This new understanding enriches the conservation of artworks and enhances our comprehension of art history.
Top image: The “Mona Lisa” by Leonardo Da Vinci
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