Seeing the World in a Dot of Paint

“Illumination: Revealing the Secret Chemistry of Oil Paintings”
Brookhaven National Lab’s National Synchotron Light Source II, above, has been helpful in identifying how paint deteriorates over time. Its extremely bright X-rays were recently used to analyze a sample from this Jan Van Eyck diptych, below, of “The Crucifixion” and “The Last Judgment,” from about 1440 to 1441, in the Metropolitan Museum of Art’s collection.

Science and art have had a symbiotic relationship throughout history. Now, a national leader in the study and research of nuclear and particle physics, not far from our own backyard, has shared its technology to help scientists at the Metropolitan Museum of Art analyze paint from a 15th-century canvas to better understand conservation techniques.

Three of the scientists involved in the endeavor — Silvia Centeno from the Met and Karen Chen-Wiegart and Juergen Thieme, from Stony Brook University and Brookhaven National Lab, will participate in a discussion of the technology and their findings in a casual cafe atmosphere at the Parrish Art Museum in Water Mill Friday at 7 p.m.

“Illumination: Revealing the Secret Chemistry of Oil Paintings” is an extension of PubSci, a popular series organized by B.N.L. in which its scientists discuss the latest developments in their research in informal surroundings. The museum will set up its theater as a pub-like setting and offer a special menu of snacks and beverages, including a variety of international and domestic beers, for purchase.

Friday’s discussion will focus on Jan Van Eyck’s “Crucifixion,” from about 1440, and a tiny sample of its paint that was examined by Brookhaven’s National Synchrotron Light Source II, which was completed in 2016. The technology is essentially an ultrabright X-ray microscope that can be used in a wide variety of applications, including chemistry, biology, and astrophysics. Created to produce the brightest source of X-rays in the world, it is open to national and international researchers, said John Hill, the facility director, in a video produced after its opening.

Their examination of the paint helped explain how and why some works of art degrade, and raises questions of how they might be better preserved. According to Ms. Centeno, “The results that we got in the experiments performed at B.N.L. moved us a step forward towards understanding a very complex deterioration process.”

“Now we have techniques that allow us to see how the reactive components in the paints segregate during the chemical reactions with a very high level of detail,” she said in an email. “This information is an important piece of a puzzle that we need to put together to understand the mechanism of the process.”

There is still be more work to be done before they devise specific recommendations for preservation, but important hypotheses have been confirmed by the examination. These include the role of high relative humidity in the acceleration of the formation of tiny bits of metal soap underneath the surface of paintings, which when accumulated can cloud the surface. The soaps are the result of the fatty acids in oil paint bonding to metals present in the pigments — such as zinc and lead — in the same way fatty acids bond with sodium or potassium to make hand soap. 

One of the most common techniques of cleaning paintings is with water. But if humidity contributes to the soap formation, doing so could make the problem worse. Ms. Centeno said that they are “also looking into what the effect of solvent-based treatments may be.”

In a paper presented last year after the examination, Ms. Chen-Wiegart wrote, “The results presented set the stage for improving the information extracted from samples removed from works of art and for correlating observations in model paint samples to those in the naturally aged samples, to shed light onto the mechanism of soap formation.”

Ms. Centeno said the Met was one of the first outside researchers to have access to Brookhaven’s synchrotron. As synchroton-based techniques have continued to develop, “they have been used to answer questions about the conservation of works of art for many years.”

There is no one correct method of examination for this conservation problem. “Different techniques complement each other.” The X-ray technology used at B.N.L. “gave us information on the distribution of elements and compounds that take place in soap deterioration in a microscopic sample with a higher spatial resolution than possible by conventional methods.” 

This gave the scientists the ability to distinguish compositional differences in smaller areas. “This information is important for understanding the mechanism of the deterioration. The techniques are non-destructive, so the samples can be preserved for future studies.” They were also able to probe “the elemental and molecular constituents below the surface of the sample at different depths,” which is not possible using conventional techniques.

Since the paints used in the Van Eyck piece were commonly used in Old Masters paintings, their discoveries could have broad application across the period and geographic regions where such paints were used. Further, these techniques also can be used to address conservation issues that have arisen from more recent periods.

“Synchrotron-based techniques are extremely powerful and will continue to be used to study works of art from different periods,” Ms. Centeno said. “In fact, with our colleagues at B.N.L. and at the University of Delaware we have been awarded beam time for the month of October to study soap deterioration occurring in modern and contemporary paintings that contain zinc-based pigments.”

At 6 p.m., preceding the program, the Parrish will offer a curator’s talk in the galleries. Admission is $12, $9 for senior citizens, and free for members and students. Reservations have been recommended.