Benjamin Franklin may be best known as the creator of bifocal glasses and lightning rods, but a University of Notre Dame research team suggests he should also be known for (literally) innovative ways to make money.

According to a study published this week in the journal Proceedings of the National Academy of Sciences, Franklin minted nearly 2,500,000 banknotes for the American colonies during his career, using a technique that researchers have described as highly original. .

A research team led by Khachatur Manoukian, associate professor in the Department of Physics and Astronomy, has spent the last seven years analyzing nearly 600 colonial-era notes that are part of a large collection created by Hesburgh. Rare books and special library collections. The Colonial Notes span a period of 80 years and include a number of counterfeit notes as well as banknotes printed by Franklin Printing Network and other printing houses.

Manoukian explained that the effort to print money for the nascent colonial monetary system was important to Franklin not only as a printer but also as a statesman.

“Benjamin Franklin saw that the financial independence of the colonies was necessary for their political independence. Most of the silver and gold coins brought to the British American colonies were quickly spent to pay for manufactured goods imported from abroad, depriving the colonies of adequate monetary supply to grow their economies,” Manukyan said.

But printing paper money had a serious problem: counterfeiting. When Franklin opened his printing press in 1728, paper money was a relatively new concept. Unlike gold and silver, paper money’s lack of intrinsic value meant that it was constantly at risk of depreciation. In the colonial era there were no standardized notes that allowed counterfeiters to distribute counterfeit notes as if they were real. In response, Franklin attempted to implement a number of security features that made his accounts distinctive.

“Franklin had to stay one step ahead of the counterfeiters to keep the bills credible,” Manoukian said. “But the notebook that we know recorded these decisions and printing methods is a thing of the past. Using physics techniques, we were able to partially reconstruct what this recording might have shown.”

Manoukian and his team used state-of-the-art spectroscopic and imaging tools from the Nuclear Science Laboratory and four major Notre Dame research facilities: Center for Environmental Science and Technology, Center for Integrated Imaging, Center for Materials Characterization, and Center for Molecular Structure. The instruments allowed them to take a closer look than ever before at the ink, paper, and fibers that made Franklin’s bills distinctive and difficult to copy.

They discovered Franklin’s pigments as one of the most characteristic. Manoukian and his team identified the chemical elements used for each item in the Notre Dame Colonial Notes collection. They found that counterfeit products contain noticeably high amounts of calcium and phosphorus, but these elements were found only in traces of real bills.

Their analysis showed that Franklin used (and sold) “lamp black”, a pigment created by burning vegetable oil, for most printed materials, while Franklin’s printed currency used a special black dye made from graphite found in rock. This pigment is also different from the “bone black” made from burnt bone favored by both counterfeiters and those outside Franklin’s printing network.

Franklin’s other innovation was in the newspaper itself. The invention of adding fine fibers to pulp (which can be seen as pigmented curls on paper money) is often attributed to papermaker Zenas Marshall Crane, who started the practice in 1844. But Manoukian and his team found evidence in Franklin’s paper that he used colored silk much earlier.

The team also discovered that the banknotes printed by Franklin’s net had a distinctive appearance due to the addition of a translucent material they identified as muscovite. The team found that Franklin began adding muscovite to his papers, and the size of the muscovite crystals in his paper increased over time. The team speculates that Franklin initially started adding muscovite to make printed notes more durable, but continued to add it as it proved to be a useful deterrent against counterfeiters.

Manoukian said it’s unusual for a physics lab to work with rare and archival materials, and this poses special challenges.

“Few scientists are interested in working with such materials. In some cases, these banknotes are unique. They need to be handled very carefully and not damaged. These are limitations that would turn many physicists away from a project like this,” he said.

But for him, the project is a testament to the value of interdisciplinary work.

“We were fortunate to have research students interested in both physics and art history and conservation on this project. The major research centers as well as the rare books and private collections team have been incredible research partners. Our discoveries would not have been possible without an extraordinary level of collaboration across disciplines.” Source