Artists have been painting over their old paintings for centuries because they weren't happy with the old picture, or just couldn't afford a new canvas.For years, art historians and conservators used X-rays to detect hidden paintings. But the images were murky, black-and-white representations. Now, art experts have borrowed a new tool from the world of high energy physics research, to get a better look at what's beneath the surface.
Wyeth painting uncovered
In 1919, a story called "The Mildest Mannered Man," featuring a black-and-white illustration of a fist fight, by American artist N.C. Wyeth, appeared in Everybody's Magazine. Wyeth had painted the original version of the picture for the magazine, but once it was published, he reused the canvas to paint a group portrait of his family.
"Actually, the illustration that's buried underneath was thought to have been lost in the 1920s, and it was rediscovered in 1997," said Jennifer Mass, a chemist working with the University of Delaware Art Conservation department and the nearby Winterthur Museum, whose art experts X-rayed the canvas. They found evidence of the hidden painting depicting two men fighting over which Wyeth had painted the family gathering.
Conventional X-ray imaging has limitations
"It only gives us really a very incomplete black-and white image of the buried painting," said Mass. "And that's because it's really only telling us the positions of the high density pigments, like the lead-base pigments which are absorbing X-rays strongly."
At the recent National Meeting of the American Chemical Society in Washington, Mass explained how equipment that is typically used for physics experiments can bring out more details of a long buried painting.
How the synchrotron sees more details
The Cornell University synchrotron produces an X-ray beam up to a million times more powerful than medical X-rays. The beam is tightly focused onto the painting, where different chemical elements in the paint colors each emit a distinctive X-ray signature.
"We get the X-rays that are emitted from the different pigments in the buried painting, and then from the energies of those X-rays, we can determine what chemical elements are present, and from our knowledge of the history of technology, we can go from what elements are present to what pigments must have been used," she said.
With that information they can reconstruct the hidden painting. To confirm the colors of the buried painting from the high-tech analysis, Mass says they use a much older technique of taking paint samples about the size of a period at the end of a sentence, from the canvas.
"We take these tiny samples and we mount them in cross-section, and then we can look at the paint layers under the microscope. And so we were able to take just a small number of samples from the painting and then we were able to compare to our non-destructive data."
Growing interest among US art experts
Mass says the new process, called confocal X-ray fluorescence technology, is already in use in Europe, but is just starting to catch on in the U.S.
"There's been great interest among art conservators in the United States to work at synchrotrons at Cornell University, at Stanford and at Argonne National Lab and Brookhaven [National Laboratory]. And so we do see this technique being applied to a number of different types of paintings in different locations now."
Using the new technology, Mass and her colleagues uncovered a color version of "The Mildest Mannered Man" illustration. The hues are somewhat muted, possibly because the artist was painting it for a black-and-white reproduction in a magazine. Wyeth might be astonished to learn how, almost a century later his painted-over picture was revealed.