Recipe for Success

What happens when a reliable treatment for worn paintings no longer works as well as it once did?

That is the reality faced by conservators who relied on BEVA (Berger Ethylene Vinyl Acetate) 371, an adhesive used to attach a secondary canvas to the back of worn canvas paintings in a process known as lining. BEVA had been used safely to provide support for thousands of paintings around the world since it was developed in the 1970s by conservator-restorer Gustav A. Berger. But two key ingredients in its formula went out of industrial production beginning in 2005—a stark reminder that manufacturing needs don’t always align with those of the art world—and conservators began to panic.

“Imagine a call center suddenly experiencing an influx of calls from people saying, ‘This isn’t working how it used to,’ and they’re really irritated about that,” says Chris McGlinchey, project director at New York University (NYU). “There was a swift response from conservators saying there’s something different about this formula. Its capacity to be adapted one way or another went away.”

That capacity has been restored with BEVA 371 Akron, a safer, more sustainable reformulation of the adhesive developed with the support of a conservation science research grant through the Getty Foundation’s Conserving Canvas initiative. Scientists and conservators at the NYU Conservation Center of the Institute of Fine Arts and the University of Akron (UA) School of Polymer Science and Polymer Engineering partnered to find an alternative product to fill this gap in conservators’ toolkits. The new formula behaves the way the original BEVA did, but it has a greener chemical makeup (notably without phthalates that require extra safety measures) and can be produced in different formats, like a premixed solution and solvent-free solids, to suit the needs of conservators worldwide.

“This flexibility means conservators have a choice in how they want the adhesive to work,” says McGlinchey, who led the project team. “The brilliance of BEVA is its adaptability for different uses.”

The new formula has already sparked positive feedback from the conservation community in test settings and at the American Institute for Conservation conference earlier this year. Premixed versions are now in production by distributors in New Jersey and Italy, paving the way for a new era of paintings conservation.

“Every Degree Counts”

McGlinchey spent decades as a conservation scientist at the Museum of Modern Art in New York and as a research chemist at the Metropolitan Museum of Art. When BEVA’s first missing ingredient, a synthetic resin called Laropal K-80, went out of production in 2005, he recalls investigating the ways BEVA had been used to treat artworks of different mediums early in his career. (Cellolyn 21E, a tackifier additive that helped produce the adhesive’s sticky quality, is the second missing component and was discontinued in 2020.)

One of the biggest issues that became apparent was the need to heat the adhesive above its recommended higher temperature of 65°C (149°F) to 70°C (158°F). This creates a more viscous consistency, which, along with the elevated heat, could potentially put artworks at risk. “Every degree counts,” McGlinchey says. “In order to observe just how different the formula became, it was essential to listen to those who had worked with the material back in its heyday of the late 1970s and ’80s.”

To do this, the team collected feedback from international conservators skilled in working with the material to identify which qualities mattered most when lining paintings. They also studied the original formula and sourced potential new ingredients that would be most compatible with the rest, all with the goal of developing a solution that would allow art restorers to achieve their desired results at a lower temperature and withstand future potential supply chain shortages. Then, it was time to experiment.

Solid, Liquid, Film?

Dharamdeep Jain, a postdoctoral researcher in polymer science, was among the team at UA tasked with analyzing the original recipe and creating new formulations. Serving under Dr. Ali Dhinojwala, W. Gerald Austen Endowed Chair and H. A. Morton Professor in the College of Engineering and Polymer Science, Jain spent his days researching potential replacement tackifiers, mixing new formulas, and conducting tests to check stickiness at the right temperature. After narrowing down a few options, the team shared samples with conservators and specialists at museums, in private practices, and through Conserving Canvas lining workshops to assess their performance. The universal contender became known as BEVA 371 Akron.

“We processed the adhesive into solid pellets options that opened the door for ease of use and transportation,” Jain says. The adhesive was formulated as a premixed solution and solvent-free solid pellets that have a longer shelf life, can be safely shipped, and can be mixed in smaller quantities as needed. It was also developed as a solvent-free, non-woven film made of pure adhesive. “A big win in terms of sustainability are the solvent-free options, especially for conservators who are looking to experiment with new methods,” Jain adds. “These formulations allow them the opportunity to do so in a much safer way.”

The solvent-free film formula was a breakthrough during the yearslong research journey. The potential product is a nonwoven, freestanding material designed to mimic the fluffy quality of a sprayed liquid adhesive (known as “flocking” in the world of canvas lining) without the need for a spray booth or layers of personal protective equipment. It’s innovative in that it’s made entirely of adhesive with no carrier support (another win for sustainability), and it can attach to an artwork’s surface with targeted precision. “I think conservators are going to be curious about this type of product especially when it comes to textiles and paper,” McGlinchey says. “The adhesive layer can hold these materials together without creating stiffness, which is game changing for artworks that have a draped quality.”

A Serendipitous Test Subject

Dean Yoder, Lapis senior conservator of paintings and head of paintings conservation at the Cleveland Museum of Art, was one of the specialists McGlinchey approached for insights on canvas lining. Yoder has had his own conservation practice for 25 years and had worked with the original BEVA, making him a natural choice to conduct tests and lead workshops with the new formulas. He is also one of the first to use BEVA 371 Akron on a canvas painting, which fittingly depicts a scientist at work with a microscope.

When the painting, A Scientist Seated at a Desk by Candlelight, by Anna Dorothea Therbusch, came to the museum’s collection in need of relining, he knew it was the perfect opportunity to put the new formula to use. “The lining was detaching, and the adhesive last used on the entire back of the painting was akin to Elmer’s glue,” Yoder remembers. “It had just about every problem in the book, and we needed to find creative solutions.”

Yoder opted for a flocked application inspired by the mist-lining method he had learned about on a previous visit to the Stichting Restauratie Atelier Limburg in the Netherlands. This technique, which involves gradually spraying layers of an adhesive onto the back of a painting, is easily reversible, a quality Yoder greatly appreciated after his graduate intern Renata Gumkowska spent over 150 hours carefully peeling off the original thick glue lining. In addition to successfully lining the painting with the new BEVA, he and his team uncovered the artist’s signature and a date that places the work earlier in Therbusch’s career than previously thought. This discovery sheds new light on the artist’s prolific career, confirming it was created at a time when she would have been caring for her children and household.

Yoder hopes the new formula will inspire further research into greener and more accessible ways to get the product into the hands of more conservators. “We all agreed that the Akron formulation’s versatility exceeded our goals,” he says. “To be able to bring in expertise from people who are at the top of their fields and get that consensus was a great moment for conservation.”

McGlinchey agrees that the connections made during the project mark an important step for the future of art conservation. The multidisciplinary collaboration reminded him of his early days at the Met, where the paintings conservation department envisioned a team of conservators, scientists, and historians who, together, would advance the work that conservators do. “That made so much sense to me that I didn’t ever have to second-guess how to use the science I know for the benefit of the field,” he says. “That human interaction—sharing knowledge, bouncing ideas off one another, and not working in a vacuum—is what this field is all about.”