New Way To Analyze Art

Raman spectroscopy is an increasingly popular method for analyzing pigments in artwork. Surface-enhanced Raman spectroscopy, which uses a metal such as silver to boost the Raman signal, improves the sensitivity of normal Raman and allows smaller samples to be used, but SERS has not previously been applied to artwork. Richard P. Van Duyne of Northwestern University, Francesca Casadio of the Art Institute of Chicago, and coworkers have now used SERS to analyze pigments in a variety of media, including six pastel sticks that belonged to the artist Mary Cassatt and a pastel artwork by Cassatt (Anal. Chem., DOI: 10.1021/ac901219m). They succeeded by coating single grains (1–6 μm) of pigment with silver colloids, instead of putting samples on a silver surface, as done previously. In "Sketch of Margaret Sloane, Looking Right," SERS revealed colorants in the ruff that couldn't be measured with normal Raman.