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Medical laser system probes ancient art

A laser system developed by Duke researchers for medical imaging may be the key to revealing secret details of ancient art.

Strolling through an exhibition on the detection of art forgeries at the National Gallery in England, Warren Warren, director of Duke’s Center for Molecular and Biomolecular Imaging, realized that the potential of the optical imaging technology—originally developed for medical diagnosis of body tissue—extends beyond the scientific realm. The laser could also image the delicate layers of artwork.

“For the most part, they were using decades-old technologies [to detect forgeries], and that suggested an opportunity if we brought state-of-the-art medical techniques to bear,” Warren wrote in an email Monday. “What we do with tissue is high resolution, depth resolved imaging and there are no methods in convenient use on art that would do the same thing.”

The laser system identifies the precise pigments and layering techniques of the artist and distinguishes between the man-made and natural versions, said Martin Fischer, assistant research professor of chemistry and co-developer of the imaging system.

“It is likely we will examine photo-degradation in a famous Matisse painting,” said Warren, who is also James B. Duke professor of chemistry. “This tool has a real opportunity to provide different information.”

In contrast to a laser pointer, which shoots a constant beam, the team developed a laser which sends out noncontinuous high power pulses—a “picket fence” of energy bursts, Warren said.

These short bursts enable the laser to see extremely weak signals of light bouncing off objects, he noted. This technology could even be employed to uncover the identity of the artist. Because the laser is so sensitive, it is able to distinguish the specific fingerprints of pigments of paint, as well as the materials and textures artists use and create.

Sarah Schroth, Nancy Hanks Senior Curator at the Nasher Museum of Art, noted that the laser system will facilitate the analysis of artwork.

“It may help to identify techniques—say if the wood of a panel painting or a sculpture is identified as from a particular type of walnut tree common in Germany, it might narrow the field,” Schroth wrote in an email Thursday.

Obstacles encountered in creating the microscopy technique included the need to create a system that has high spatial resolution and acute penetration, Fischer said. A common difficulty, he noted, was imaging superimposed, thin layers of paint—a characteristic of many famous paintings, like the Mona Lisa.

“A special challenge was the sensitivity—while in a synthetic sample you might get away with turning the laser power higher to get more signal, in a priceless historic work of art one has to be sure no permanent damage occurs,” he said.

The next step in his research, Warren added, would be the development of a portable model—a feat possible now that the parameters of the laser system are known. The current version takes up a four-foot by 12-foot table, but a hand-held laser of this ability would facilitate the analysis of ancient artwork without depending on external sources.

Although the laser system is one of the more non-destructive ways of analyzing artwork, there is still some skepticism among those who are more conservative, Schroth noted.

“In the future, when it is widely accepted as safe for artworks, the laser will be enormously helpful in the conservation of works of art, primarily painting and sculpture,” she said.

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