Can tech sort fake Rembrandt from real?

June 23, 2008 9:44:16 AM PDT
Perhaps it was the reassuring smile that convinced a buyer to drop $4.5 million on a painting that experts had panned as a fake. The portrait of a "laughing" Rembrandt sold in October at a British auction house was considered the work of a follower, rather than the master, and was valued at $3,100. But last week, an investigation by the Rembrandt Research Project confirmed that it was indeed a self-portrait by the legendary painter himself.

While the high-stakes process of authenticating famous artwork isn't quite foolproof, new technologies have allowed investigators to probe masterpieces in novel ways. X-rays, for instance, revealed another painting beneath the self-portrait that exhibited qualities similar to other Rembrandt paintings, evidence that evaluators were unable to discern.

Museums have typically determined authenticity by polling historians and other scholars until a consensus is reached. Experts, however, can sometimes disagree, get it wrong or even end up stumped. During the 1930s and '40s, an artist named Han Van Meergeren duped the art world and made millions by passing off his forgeries as the work of well-known artists.

"We rely on connoisseurship incredibly, but it's also the most fallible of all things," says Scott Schaefer, a curator at the J. Paul Getty Museum. "And in the balance hangs thousands, sometimes millions of dollars."

Forensic science emerged as way to better spot knock-offs. The combination of carbon dating, X-rays and other hi-tech tools can uncover the age of the canvass, the chemical makeup of color pigments and purity of the materials ? all of which should coincide with the purported era the piece was created.

Still, "a scientific analysis," Schaefer says, "can only tell you that the painting was of a certain time period, but that doesn't get you very far."

Much of the headache with attribution can be blamed on a common practice during Rembrandt's time in which students were encouraged to be artistic clones of their mentors. Nearly everything ? from the teacher's technique to the types of paint used ? was often copied with the instructor's approval. Artists would sometimes even put their signature on an apprentice's work to earn extra cash.

While scientific methods have done a good job in some respects to solve questions over authenticity, they haven't done as well in figuring out just who did a particular work of art, says Sharon Flescher, Executive Director of the International Foundation of Art Research (IFAR).

Dan Rockmore, a mathematician at Dartmouth University, believes that digital technology may change all that. After spending much of his academic career searching for ways to connect aspects of everyday life to the abstract world of numbers, he has focused his attention on showing that art has a mathematical signature.

His idea came during a trip to the Metropolitan Museum of Art back in 2001, when he caught a glimpse of how curators distinguished between the real from the bogus. As he toured the exhibit, which featured the drawings of Pieter Bruegel the Elder, and listened as a curator pointed out the subtle details that set Bruegel's strokes apart from his imitators, he pondered: "Can we quantify what a connoisseur does?"

He soon put the question to the test by first digitizing slides from the exhibit, eight actual Bruegel sketches and five drawn by other artists. From there, Rockmore converted the pictures into statistical representations that he fed into software designed to locate patterns and trademarks as slight as the one-of-a-kind swoosh of an illustrator's pen.

"Different artists simply have different ways of generating lines. Some will make few or denser lines than the other," explained Rockmore. "You can see statistical differences in that."

The findings, reported in the Proceedings of the National Academy of Sciences, demonstrated that the computer was able to correctly pick out the eight actual Bruegel drawings based on the similarity of mathematical trademarks.

Even as he looks to build on the study's promising results, the rational-minded professor thinks we are still short of installing digital connoisseurs in galleries. The computer hasn't fared so well outside of drawings and to analyze complex works like paintings, he says, would require "significantly more development." '

"There was a time that no one was using x-ray imaging to determine the authenticity of a work of art, but now it's an accepted method," he added.

But for now, as flawed as it may seem, Shaeffer says, "it often falls on more mundane things like two eyes."