Northwestern chemist investigates lost reds in Home...(rom 800 to 1350 A.D. Our research ...)

"Our research provides an entirely new window onto the analysis of artworks," said Van Duyne. "There's a broad range of physical science methods used in the conservation business. The trick is you can't harm the work -- the method has to be non-destructive or minimally destructive. Conservators do a lot of work with X-ray photography and infrared photography, but those techniques don't tell you what elements are present. The Raman technique tells you about what molecules are there."

In preparing for the Art Institute's major Homer exhibition, conservators discovered, using X-ray fluorescence spectrometry and visual examination through a microscope, that the painting's white skies were originally painted in unstable red and orange dyes that have almost completely faded.

In discerning the painting's original colors, Van Duyne's team must figure out a reliable way of preparing microscopic watercolor samples for SERS analysis. In the end, Art Institute conservators won't repaint the original skies but, in conjunction with the Homer exhibition, they created a digital image that offers viewers an idea of the artist's intentions. (View the digital simulation of "For to be a Farmer's Boy" at http://www.artic.edu/aic/collections/exhibitions/homer/resource/624.)

Van Duyne says that conservation scientists are unlocking the secrets of dye and pigment analysis, and that in the future such analysis will help conservators determine forgery, authenticity, exact provenance and best restoration methods. "If we have a better idea about which materials are used in paintings, for instance, we'll have a better idea of how to restore them. Just identifying what's involved is a very important step."

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