Richard Van Duyne, Nilam Shah and colleagues explain that the challenge for analyzing inks on historical documents is that there's often very little of it to study. Another complication is that plant- or insect-based inks, as well as some synthetic ones, are composed of organic molecules, which break down easily when exposed to light. Current methods are not very specific or sensitive or can leave a residue on a document. To address these issues, the research team set out to develop a different way to analyze and identify historical inks.
They used the novel method, called tip-enhanced Raman spectroscopy (TERS), to analyze indigo and iron gall inks on freshly dyed rice papers. They also studied ink on a letter written in the 19th century. "This proof-of-concept work confirms the analytical potential of TERS as a new spectroscopic tool for cultural heritage applications that can identify organic colorants in artworks with high sensitivity, high spatial resolution, and minimal invasiveness," say the researchers.
The authors acknowledge funding from the Andrew W. Mellon Foundation, the Grainger Foundation and the National Science Foundation.
Science Daily. 2014. “New method to identify inks could help preserve historical documents”. Science Daily. Posted: June 18, 2014. Available online: http://www.sciencedaily.com/releases/2014/06/140618122257.htm