Benjamin Franklin's Anti-Counterfeiting Technique

Inventor Benjamin Franklin devised many unique measures to prevent the production and circulation of counterfeit money in America in the 18th century.

The researcher examines the note under the spectrometer. Photo: University of Notre Dame

Benjamin Franklin is best known for inventing bifocals and lightning rods, but a team of researchers from the University of Notre Dame points to him developing anti-fake technology. During his career, Franklin printed nearly 2,500,000 banknotes for the American colonies, using a unique technique described in research published July 17 in the journal Proceedings of the National Academy of Sciences.

The team, led by Khachatur Manukyan, an associate professor in the Department of Physics and Astronomy, spent seven years analyzing nearly 600 colonial-era banknotes from the Hesburgh Library's Rare and Special Items collection. . Colonial bills circulated for 80 years, including prints from Franklin's network of printing presses as well as a series of counterfeit bills.

Manukyan explained that the attempt to print money for the nascent colonial monetary system was important to Franklin. "Benjamin Franklin saw that financial independence was essential for the colonial states to achieve political independence. Most of the gold and silver coins brought to the British colony in the Americas were quickly exhausted to pay for goods imported from abroad, leaving many colonial states without enough money to expand their economies," Manukyan said.

However, a major problem hindering efforts to print banknotes is counterfeit money. When Franklin opened his printing press in 1728, paper money was a relatively new concept. Unlike gold and silver coins, paper money lacks intrinsic value and is constantly in danger of depreciating in value. Without a standard money system in the colonial era, speculators had the opportunity to circulate counterfeit money. In response, Franklin developed a series of security features to identify real money.

Manukyan and his colleagues use advanced imaging and spectroscopy equipment at the Laboratory of Nuclear Science and four core research facilities at the University of Notre Dame, including the Center for Environmental Science and Engineering, the Mechanical Integrated imaging facility, Material characterization facility, and Molecular structure facility. These tools allowed them to take a closer look at the ink, paper, and fibers that made Franklin's banknotes so special and difficult to emulate.

One of the most remarkable features the team found was Franklin's pigment. Manukyan et al identified the chemical elements used in each of the colonial banknotes in the collection. The counterfeit coins they found were high in calcium and phosphorus, but these elements were only detected in very small amounts in real money.

The team's analysis revealed Franklin used "lamp black", a pigment created by burning vegetable oil. Franklin's banknotes used a special black dye made from graphite, as opposed to the "bone black" made from burned bones favored by counterfeiters.

Another Franklin innovation was in the printing press. The invention of mixing microfibers in wood pulp to make paper, visible under the zigzag lines inside banknotes, is often attributed to paper maker Zenas Marshall Crane in 1844. But Manukyan's team found evidence that Franklin inserted colored yarn into money paper much earlier.

The researchers also discovered that banknotes printed by Franklin's network of workshops had a distinct shape due to the addition of a transparent material they identified as muscovite. According to them, Franklin began adding muscovite to the banknotes and the muscovite crystal size increased over time. The team speculated that Franklin initially added muscovite to make printed money more durable but continued to add more when the feature became useful in preventing counterfeit money production.