Public Release: 

Naples Yellow: An old pigment adds a new shade to authenticating art

American Institute of Physics

Authenticating artwork is a complex task that has historically required experts who have the knowledge of an art connoisseur and the eyes of a detective. In recent decades, however, chemistry and physics have helped transform the previously subjective skill into a more objective pursuit. Analytical techniques for authenticating art are growing ever more critical in light of new European laws which place greater liability for misidentified works on art merchants.

It was with these issues in mind that Joris Dik and colleagues in the Laboratory for Crystallography at the University of Amsterdam trained a host of analytical instruments on a lead/antimony pigment known as Naples Yellow. Dik explains that throughout the history of visual arts craftsmen have perpetually sought cheaper, more stable, and less toxic pigments. Naples Yellow, in particular, was manufactured by various methods as it was incorporated into numerous paintings produced between the sixteenth and early twentieth centuries.

Dik's collaboration studied Naples Yellow samples from historical paintings of known origins from various collections, such as the Rijksmuseum in Amsterdam and the Getty Museum in Los Angeles. In addition, the researchers surveyed portions of historical pigments in the Hafkenscheidt Collection at the Teylers Museum in Haarlem (the Netherlands) and the Turner Pigment Collection in London's Tate Gallery. They examined samples with electron microscopes and identified the chemical compositions with Energy Dispersive Spectroscopy (EDS), a technique that involves bombarding a sample with electrons and monitoring the characteristic x-rays emitted by the various sample components. X-ray and synchrotron diffraction studies revealed differences in physical structures of distinct versions of Naples Yellow.

In combination with literary research into pigment production manuals and technical treatises describing manufacturing methods, Dik explains, "We are able to sketch a chronological and geographical map of the production of Naples Yellow." The map should help narrow down the origins of unidentified artworks, and potentially verify the pedigrees claimed for otherwise established works.

Dik will present the results of the study, which was sponsored in part by the Amsterdam branch of Christie's auction house, at the 2001 American Crystallographic Association meeting in Los Angeles (July 21-26).


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