When Benjamin Franklin moved to Philadelphia in 1723, he witnessed the beginning of a dangerous new experiment: Pennsylvania began printing words on paper and calling it money.
The first American paper money hit the market in 1690. The metal coins never left the 13 colonies, flowing in unceasing streams to England and elsewhere, as payment for imported goods. goods Several colonies began printing pieces of paper for coins, saying that for a certain period of time, they could be used locally as money. The system worked, but stopped, the colonies were soon discovered. Print too many bills, and the money becomes worthless. And counterfeiters often found the banknotes easy to copy, devaluing the genuine items with many counterfeits.
Franklin, who began his career as a printer, was an inveterate inventor who would also create the lightning rod and bifocals, found the currency attractive. In 1731, he won a contract to print £40,000 for the colony of Pennsylvania, and he applied his penchant for currency innovation.
During his printing career, Franklin produced a stream of baroque, often fine currency. He created a copper plate of sage leaves to be printed on money to destroy counterfeits: The intricate pattern of the veins was not easily imitated. He influenced several other printers and experimented with new paper and inks.
Now, on a study published Monday in the Proceedings of the National Academy of Sciences, a team of physicists revealed new details about the composition of the ink and paper Franklin used, asking which of his innovations were intended as a defense against forgery 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 such as silicon or lead based on their vibration. They also used different microscopy techniques to examine the paper the money was printed on.
Some of what they observed confirmed what historians had long known: Franklin’s paper money contained flecks of mica, also known as muscovite or isinglass. These shiny patches are likely an attempt to combat counterfeiters, who would not have access to this special paper, said Jessica Linker, a professor of American history at Northeastern University who studies the paper. which is money during this period and is not included in the study. Of course, that didn’t stop them from trying.
“They were able to make very good fakes, with mica glued on top,” said Dr. Links.
In the new study, the researchers found that the mica in the bills for the different colonies seemed to come from the same geological source, suggesting that a single mill played a role. The Philadelphia area is known for its schist, a flaky mineral that contains mica; it is possible that Franklin or the printers and papermakers associated with him collected the substance used in their paper locally, said Dr. Manukyan
When they examined the black ink on some of the bills, the scientists were surprised to find that it appeared to contain graphite. For most printing jobs, Franklin used black ink made from burnt vegetable oils, known as lampblack, said James Green, librarian emeritus of the Library Company of Philadelphia. Graphite would have been difficult to find, he suspected.
“So Franklin’s use of graphite in printing money is very surprising, and his use of banknotes printed as early as 1734 is even more surprising,” Mr. Green said in an email.
Is the use of graphite ink a way to distinguish real money from fakes? The color differences between graphite and lampblack were probably subtle enough to make that a difficult task, Mr. Green said. Instead, we may be looking at another example of Franklin’s creativity.
“This suggests to me that almost from the beginning he was using his money printing contracts as an opportunity to experiment with a range of new printing techniques,” he said.
To understand Franklin’s intent more clearly, more analysis of printed documents from the period would help, said Joseph Adelman, a professor of history at Framingham State University in Massachusetts.
“The comparison I would most like to see is Franklin’s other publications,” said Dr. Adelman. “To really test this theory – did Franklin have a separate ink shop?”
In future research, Dr. hopes. Aspire to work with scholars who have access to larger collections of early American currency. These methods can be very important in the study of history, said Dr. Linker, if scientists and historians can work together to determine the best questions to answer.
“I have questions about a whole bunch of inks. There’s a really weird green on some of the New Jersey bills,” he said, referring to money printed by a Franklin contemporary. “I want to know where that green ink was made.”
