Kate Duffy, a conservator at the Williamstown Art Conservation Center, presented a lecture entitled “Exposing Forgery through the Art of Chemistry” last Thursday. The lecture was organized by the chemistry department to coincide with National Chemistry week.
Duffy stressed the interdisciplinary aspects of her field, saying that a “museum scientist is a generalist,” who needs “at least a slight knowledge of” fields other than chemistry such as physics, art history and biology. She described her role in exposing forgeries as twofold. First, she assists the curator in the examination of the object. Second, she authenticates the integrity of a work by analyzing the materials in the object. She noted that it is crucial that she “work in collaboration with the curator.”
Duffy described what she termed the “battery of analytical instrumentation taken from industry and tweaked” she uses to examine art. She discussed three instruments: x-ray fluorescence (XRF), FTIR and the scanning electron microscope (SEM). With these various tools, conclusions are typically drawn from comparisons with known data about the chemical makeup and construction of art during certain time periods.
“The XRF is the curator’s dream instrument,” Duffy said. She went on to explain how XRF is preferable to other analytic instruments because no sampling of the artwork is required. The technique, therefore, does not destroy the object being tested. XRF is typically used in order to ascertain what type of pigment was used or to distinguish various metals contained in the piece. Since different types of pigments were used in different eras, and museum scientists are able to more closely date a piece through chemical analysis. The FTIR uses infrared rays in order to analyze the pigments in a method similar to the XRF. According to Duffy, “it is a destructive technique, but because the samples are so small, it doesn’t usually pose a problem.”
The final piece of Duffy’s array of instruments was a scanning electron microscope (SEM), which provides both three-dimensional photographs in a high resolution and performs elemental analysis. Throughout her presentation, Duffy gave several examples of artworks that served to depict the various techniques of the instruments she described.
Her final example dealt with the way in which all of the instruments work in conjunction with each other. She brought a sculpture of St. Jerome which had been given to the College as a gift to use as an example. While the donor had commissioned an appraisal of the work which dated it to the 17th century, evidence from Christie’s auction house made curators suspicious that the work could actually be a 20th century piece. Four similar pieces had been placed on the auction block at Christie’s, but were pulled off at the last moment because they turned out to be made in the 20th, rather than the 17th, century.
While still unsure about the St. Jerome sculpture’s origin, Duffy did not hesitate to point out that the complete analysis was ongoing, and laboratory evidence as well as curatorial doubts have raised suspicions that the piece is more recent than it was purported to be.
An x-ray revealed 20th century nails in the piece, which either demonstrate that the sculpture is modern or indicate that it has been repaired recently. There are no results yet from the pigment analysis, but when complete, Duffy expects to be able to pinpoint the age of the piece much more accurately.
She pointed out, however, that “it’s very difficult to have a piece shown to be a forgery” since there can always be an alternate explanation for certain modern elements in the piece. She also said that “analytical results are only one piece in the whole pie,” and the results that she finds in the laboratory must be used in conjunction with visual and historical evidence regarding the piece.