We Talk Art, And Immunosorbent Assays, With Fang Ren '14

If you're a collector or conservator of art, it behooves you know what your art is made of. That helps you store it properly, and could even keep you from getting ripped off by unscrupulous dealers. 

So, fortunately, there is the enzyme-linked immunosorbent assay (ELISA). This test, which uses antibodies and color change to identify a substance, was one of the tools that Fang Ren used in as a postdoctoral researcher at the Metropolitan Museum of Art in New York. ELISA goes back to the 1960s and is widely used to analyze medications, for blood tests, and to check for food allergens. Increasingly, it has been used to examine materials used in paintings and other kinds of artworks.

“It’s important to help us understand art history,” said Ren, who worked in Prof. Lisa Pfefferle’s lab and received her Ph.D. in Chemical Engineering at Yale in 2014. “It can help you tell what the date of the artwork is and can contribute the information to art history. It might also give you information about whether the art is authentic.”

Casein is one of the main substances she has detected with ELISA. It’s a protein that’s derived from milk. Its use goes back to prehistoric times and is found in some cave paintings, and remained a popular material for painting into the 20th century. Colin Campbell Cooper’s 1908 painting of the Flatiron Building (to the left) is an example of the use of casein.

By the second half of the 20th century, acrylics largely took over as the preferred material for painters. But some artists stuck with casein, valuing its consistent texture, and it's still used today. One of Ren’s main projects at the Met was analyzing “Small Figure in Blue,” a 1964 painting by Israeli artist Michael Gross, who used casein for many of his paintings. “He mixed the casein with other pigments to make the blue,” Ren said.

The use of ELISA also helps detect other materials in paintings - egg yolk and albumen, animal glues, all of which have been commonly used in art at some point. It’s important for art conservators to know if these materials are present, Ren said, for the sake of storage.

“If you find out that there are some organic pigments that are light-sensitive, they’ll want to store it in a very low-light environment, or even completely in the dark when no one’s around.”

So how do you test for proteins in historic and often priceless artwork without risking any damage? “You scratch a little from the surface,” she said. “We use tiny, tiny samples.”

Ren was with the Met until August, and is now living in California. There are only a handful of museums with research laboratories, and jobs are scarce, but she’d like to get back in the field of art analysis in the near future.