NYT: Benjamin Franklin, money printer

Via the New York Times: 

Now, in a study published Monday in the Proceedings of the National Academy of Sciences, a team of physicists has revealed new details about the composition of the ink and paper that Franklin used, raising questions about which of his innovations were intended as defenses against counterfeiting and which were simply experiments with new printing techniques.

The study draws on more than 600 artifacts held by the University of Notre Dame, said Khachatur Manukyan, a physicist at that institution and an author of the new paper. He and his colleagues looked at 18th-century American currency using Raman spectroscopy, which uses a laser beam to identify specific substances like silicon or lead based on their vibration. They also used a variety of microscopy techniques to examine the paper on which the money was printed.

Pretty interesting work; sounds like Franklin was experimenting with graphite, among other compounds.