Berkeley Lab research team identifies compound known to cause deterioration in oil paintings

Angewante Chemie/Courtesy

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Using X-ray imaging, a team of international researchers conducted a study at the Lawrence Berkeley National Laboratory, or Berkeley Lab, to investigate how one oil paint called “Soft Titanium White” and its chemical makeup may cause artwork to deteriorate over time.

Barbara Berrie and Xiao Ma of the National Gallery of Art worked on the study, alongside Georg Ramer, Georges Pavlidis and Andrea Centrone of the National Institute of Standards and Technology, among other researchers. The team examined a paint sample using 3D X-ray imaging technology at the Advanced Light Source, a U.S. Department of Energy facility at Berkeley Lab. It found that “Soft Titanium White” — which has been used in oil painting for decades — is partly composed of zinc oxide, an inorganic compound known to form “soaps” that cause deterioration.

“The initiators for the processes of soap formation are incompletely known — some may be intrinsic, others extrinsic,” Berrie said in an email. “Learning about the factors that influence soap formation will help in determining suitable standards for treatment and display.”

In her email to The Daily Californian, Berrie referenced a book about this threat called “Metal Soaps in Art” that was published earlier this year. The book is the product of a conference in March 2016 on metal soaps in art at the Rijksmuseum in Amsterdam, according to Berrie.

“Metal Soaps in Art” estimates that about 70 percent of paintings in museum collections are “affected by some form of metal soap-related degradation.” The book also discusses recent advancements in the detection and characterization of compounds, such as zinc oxide, that could potentially cause deterioration. Soaps formed by heavy metals such as zinc threaten famous artwork around the world.

The international team of researchers that examined a sample of “Soft Titanium White” has not yet found physical deterioration in the paintings that it has examined. The team found, however, that if the soaps were to localize in future, the concentration would cause paint fragmentation and chipping, according to a news release from Berkeley Lab.

Beyond future research into oil painting conservation, Berrie said she thinks it would be interesting to apply the new techniques to examine the “efficacy of consolidants,” meaning that it may be possible to use similar imaging to study interactions between the adhesives and consolidants used in conservation and artwork of any material.

“Application of state of the art instrumentation to (study) works of art is an exciting challenge from both the point of view of mastering the technique and of interpreting the results since objects are materially complex,” Berrie said in the email. “The reward is that it helps us connect to and take care of our material heritage.”

Contact Rachel Barber at [email protected] and follow her on Twitter at @rachelbarber_.