US founding father Benjamin Franklin developed paper money innovations long before historians previously thought such methods were in use – and they may have even had use as anti-counterfeiting measures.
Khachatur Manukyan at the University of Notre Dame in Indiana and his colleagues analysed the structure and chemical composition of more than 600 banknotes printed by Franklin and associates between 1709 and 1790. For comparison, they also performed similar analyses on paper money printed by other printers and counterfeiters.
They found that Franklin and his associates began adding indigo-dyed blue fibres and threads to paper money as early as 1739 – more than a century before the invention is traditionally credited as having been developed by paper manufacturer Zenas Marshall Crane. For the first time, the study also revealed that Franklin used a natural graphite-based black ink to print money, whereas other printers and counterfeiters at the time relied more on inks produced by burning vegetable oils or charring bones.
“These [coloured fibre] techniques have been used later on in printing federal dollars, and then other currencies all over the world,” says Manukyan.
The researchers examined the chemical make-up of the inks, fibres and paper used in Franklin’s printing processes. They also used electron microscopes to study the physical structure of printed banknotes in minute detail – a process that required the researchers to carefully extract and scrutinise paper money samples hundreds of times thinner than a human hair. They used such small samples to avoid unnecessary damage to the historic artefacts, says Manukyan.
The analysis also showed that Franklin incorporated flakes of the translucent mineral muscovite into paper pulp as a way of strengthening the durability of paper money as early as 1754.
The findings “make a nice addition to Franklin’s practical scientific resume of accomplishments”, says Farley Grubb, an economist at the University of Delaware and author of The Continental Dollar: How the American revolution was financed with paper money.
But Grubb is more sceptical of the idea that these ink and paper innovations were intended to help prevent counterfeiting. He described colonial America as having more cases of people counterfeiting coins instead of paper money, and says that counterfeiting paper money on a large scale was a “rarity” at the time.
The most notable counterfeiting attempt came during the American revolutionary war, when the British copied and mass-produced Continental dollars issued by the Continental Congress as “a new type of state-to-state warfare”, says Grubb. But he says the Congress recalled and replaced the affected bills.