Innovative ToF research on chemical processes in old paintings
Caroline Bouvier likes to look beyond the image. Or more accurately, beneath it. A postdoctoral researcher from Paris, she is less interested in what a painting depicts—the iconography—than in the chemical processes behind the composition.
It’s not that she doesn’t have an eye for the beauty or the art-historical value of a work— far from it. But her research in Maastricht focuses on identifying the materials used in old paintings by applying state-of-the-artToF-SIMS (time-of-flight secondary ion mass spectrometry). The ultimate aim? Helping to preserve art by gaining insight into its underlying chemical composition.
“This is a very important area in art conservation. It helps us to understand how paintings are preserved, which is of great importance to society all over the world. The ToF-SIMS imaging technique has been around for four decades, but in my field, interdisciplinary ‘heritage science’, it’s only been used for 20 years or so,” says Bouvier in her office at the Faculty of Health, Medicine and Life Sciences (FHML). “Paintings age, which can completely change their appearance.” Conservators play an important role in pinpointing what causes the ageing, decay and deterioration of a painting, and whether it can be slowed down or even prevented.
Botticelli’s Venus
The average person might be surprised to learn that the pigments of world-famous paintings, such as Botticelli’s Venus, are largely held together by egg yolks. “I wouldn’t go so far as to compare them with mayonnaise,” Bouvier says, laughing, “but the fact is that many of the pigments in paintings from Botticelli’s era [1445–1510] were full of egg yolk. So it’s important to find out how egg yolk remains stable over time; after all, it can occasionally react to elements in its environment and break down. A painting is a living object that needs more and more care as it ages.”
Bouvier looks, literally, ‘behind the scenes’ of a canvas. Using advanced technologies, she aims to find out how paintings were made and thus how long it will take for the often inevitable decay to set in. “I’m fascinated by the material; the more you understand about it, the more impressive the art becomes. Curiosity is what drives me. I want to know what a painting is made of. Demystifying the beauty of paintings doesn’t affect my admiration in the least. All matter is made up of molecules; even feelings are formed by molecules, and that doesn’t make them any less real. On the contrary—for me, that knowledge only enhances the intrigue.”
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Antibodies in paint samples
The name of Bouvier’s Marie Skłodowska-Curie project is quite a mouthful: Synergistic Combination of Immunolabeling and Molecular Imaging Technologies for Art Research (SCIMITAR). In a nutshell, it involves taking paint samples from artworks dating from the 15th to the 17th centuries and making visible the proteins in their binding materials (such as glue or egg yolk). Bouvier does this by means of immunohistochemistry, a technique that uses antibodies to visualise proteins in tissues. The ToF-SIMS technique also enables her to identify inorganic pigments, organic dyes and other binding materials, such as oil. This way, Bouvier can identify almost all the materials used in a painting.
Even paintings that are hundreds of years old are subject to ongoing chemical processes. “That’s why exposing a painting to light, like a flash from a camera, can damage the work.” She laughs. “Sometimes I see it as detective work. We investigate how the work was made and what chemical processes are involved, right down to the smallest detail.”
Kindred spirits
Bouvier is supervised by Sebastiaan Van Nuffel and Giuditta Perversi at the Maastricht MultiModal Molecular Imaging Institute (M4i) at the FHML. She also collaborates with SRAL, the conservation institute of the Bonnefanten Museum. “So I zip from one side of the city to the other,” she says. “And I work with the Rijksmuseum in Amsterdam and the Courtauld in London. This research gives us insight into preservation and tools that will help us conserve artworks for the longer term. The method is not yet in routine use. The idea is that my research results can be used to drawn up new guidelines, instructions and protocols for other conservators who want to try their hand at ToF-SIMS.”
For Bouvier, the project brings all her interests together. “My love of analytical chemistry, my passion for art and my belief in conservation. As a child, I collected all kinds of things; my room was a total mess. I was always drawing. Actually, I wanted to be an illustrator, but then I stumbled across chemistry, which didn’t feel at all alien to me. The conservation of art raises far-reaching issues, such as the ethical question of what it’s worth to us as a society. My answer to that question is easy to guess. Thankfully, I meet many kindred spirits here in Maastricht, which helps me stay positive and keen to continue my research.”
Text: Ludo Diels
Photography: Philip Driessen
The conservation of art raises far-reaching issues, such as the ethical question of what it’s worth to us as a society. My answer to that question is easy to guess.
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