Not just a $100 bill, more things link Benjamin Franklin to the US currency

Combatting counterfeit notes

The 600 notes analyzed also include notes printed at Franklin’s printing shops and a series of counterfeit notes. Money counterfeiting in pre-Federal America flourished, and Franklin took up this cause by inventing new production measures. 

The scientific analysis by the researchers takes a deep dive into how Franklin safeguarded bills, their materials, and historical instances of money manufacturing. 

“Benjamin Franklin saw that the Colonies’ financial independence was necessary for their political independence. Most of the silver and gold coins brought to the British American colonies were rapidly drained away to pay for manufactured goods imported from abroad, leaving the Colonies without sufficient monetary supply to expand their economy,” Manukyan said.

In 1727, Franklin opened his first printing house. Money made from paper was a new concept, with no standardized bills in the Colonial period. There was ample opportunity for people to pass off fake bills as real ones. In response, Franklin worked to embed a suite of security features that made his bills distinctive, per the Notre Dame press release.

“To maintain the notes’ dependability, Franklin had to stay a step ahead of counterfeiters,” said Manukyan. “But the ledger where we know he recorded these printing decisions and methods has been lost to history. Using the techniques of physics, we have been able to restore, in part, some of what that record would have shown.”

Franklin's new techniques

Using spectroscopic and imaging instruments, the researchers found several qualities in Franklin’s bills that made them so hard to replicate.

Some of the study's key findings revealed that Franklin used “lamp black,” a pigment created by burning vegetable oils to print the notes, and that the printed currency had a special black dye made from graphite found in rock. Franklin even innovated a new paper to print notes on. The paper was made up of tiny fibers in paper pulp, which to date was credited to paper manufacturer Zenas Marshall Crane. But Manukyan and his team found evidence that Franklin was including colored silks in his paper much earlier.

The team also discovered that the notes printed in Franklin’s network had a translucent layer of muscovite, which he added to notes over time. This was because muscovite made the paper durable and was a helpful deterrent to counterfeiters.

“Few scientists are interested in working with materials like these. In some cases, these bills are one-of-a-kind. They must be handled with extreme care, and they cannot be damaged. Those are constraints that would turn many physicists off to a project like this,” said Manukyan.

The study was published in the Proceedings of the National Academy of Sciences.

Study abstract:

Benjamin Franklin was a preeminent proponent of the new colonial and Continental paper monetary system in 18th-century America. He established a network of printers, designing and printing money notes at the same time. Franklin recognized the necessity of paper money in breaking American dependence on the British trading system, and he helped print Continental money to finance the American War of Independence. We use a unique combination of nondistractive, microdestructive, and advanced atomic-level imaging methods, including Raman, Infrared, electron energy loss spectroscopy, X-ray diffraction, X-ray fluorescence, and aberration-corrected scanning transmission electron microscopy, to analyze pre-Federal American paper money from the Rare Books and Special Collections of the Hesburgh Library at the University of Notre Dame. We investigate and compare the chemical compositions of the paper fibers, the inks, and fillers made of special crystals in the bills printed by Franklin’s printing network, other colonial printers, and counterfeit money. Our results reveal previously unknown ways that Franklin developed to safeguard printed money notes against counterfeiting. Franklin used natural graphite pigments to print money and developed durable “money paper” with colored fibers and translucent muscovite fillers, along with his own unique designs of “nature-printed” patterns and paper watermarks. These features and inventions made pre-Federal American paper currency an archetype for developing paper money for centuries to come. Our multiscale analysis also provides essential information for the preservation of historical paper money.