WHY IS US CURRENCY GREEN?
This documentation is primarily courtesy of a case brought before the New York Supreme Court in 1865- Tracy R. Edson vs The American Bank Note Company. In this case, numerous primary documents explain in painstaking detail why the color green was chosen for American currency. With a little further digging, more of the backstory was revealed as well.
It all started with a Canadian- Dr. Thomas Sterry Hunt. In 1857, at the behest of the president of the City Bank of Montreal, William Workman, Dr. Hunt developed and patented (in Canada) a new anti-counterfeiting ink. You see, the City Bank of Montreal, like so many other banks, issued their own notes. As was the case with other institutions of the day, their notes suffered from rampant counterfeiting thanks in part to the advent of certain photographic technologies.
Enter another Canadian- George Matthews. Upon learning of this new anti-counterfeiting ink, Matthews almost immediately purchased the rights to it from Hunt. He then turned around and patented the ink in the U.S. (patent #17688) claiming he'd invented it and explaining the ink was made from:
.calcined green oxide of chromium, (known to chemists as the anhydrous sesquioxide of chromium,) which I mix with burned or boiled linseed-oil, sometimes called printers varnish, in the manner usual in preparing ink for printing bank-notes or other instruments by either of the above processes of printing.
After patenting it in the United States, Matthews turned around and licensed all rights to this patent to one Tracy Edson, who along with his cohorts (Rawdon, Wright, and Hatch) within a year would partner up with several other of the most prominent security printers in the United States to form the American Bank Note Company in 1858.
But we're getting ahead of ourselves. Upon acquiring exclusive rights to the ink, Edson and co. wasted no time in investigating whether this ink really did make bank notes printed with it in a certain fashion impervious to counterfeiting. They soon announced in the following letter (which also explains why this ink was thought so special over others) that they had a method to finally beat counterfeiters :
To the Banking Institutions of the United States:
In consequence of the great danger to our paper currency from successful counterfeits, made by photography and kindred processes, it has become evident that a NEW SECURITY is needed, which, while it shall perfectly protect our bank notes from photographic imitations, and from alterations in their denominational value, shall, at the same time, preserve that security which is always afforded by artistic and highly finished engraving.
The undersigned beg leave respectfully to announce to the Banking Institutions of the United States, that they have carefully investigated this subject, and that they are now prepared to furnish the most perfect possible protection against all the above descriptions of fraud.
The process consists in the use of TWO PERMANENT INKS, conjointly, in printing bank notes, and other documents representing value. One of these is the ordinary BLACK bank note printing ink, which, having a basis of carbon, is insoluble and indestructible; the other is an equally insoluble and indestructible GREEN-COLORED INK, which cannot be removed from the paper, without also removing the black ink, and thus destroying the note.
It is an established principle in photographic chemistry, that red, yellow, and green colors act upon the photographic plates almost precisely like black; so that lines or figures of these colors will appear black in photographic copies. The use of colors, has therefore, been resorted to as a protection against photographic counterfeiting. Unfortunately, however, all the colored inks heretofore used upon bank notes, for this purpose, as red, yellow, and blue, can be removed with more or less facility, by chemical means, without disturbing the note itself, when printed in the black carbon ink. These colors being removed, the black can be copied by photography and the colors being afterwards added by lithography, or otherwise, a COUNTERFEIT is obtained, which is the more dangerous from the fancied security afforded by the colors.
The use of fugitive black or blue inks, printed upon a colored ground, has been resorted to as a protection against photography. But these inks are liable to fade on exposure to light or air; and as it is possible to efface from notes thus printed the black design, by chemical means, without disturbing the red or yellow ground, and to print another in its place, the use of fugitive inks afford great facilities for alterations; while the distinctive characteristics of the fine engraving are lost, and the note is rendered easier of imitation by the ordinary counterfeiter, and its detection more difficult.
The use of the BLACK CARBON INK above referred to, for printing bank notes, conjointly with an equally INSOLUBLE AND INDESTRUCTIBLE COLORED INK, in connection with the highest style of line engraving, would unite, in the greatest degree, the best safeguards against all the various species of fraud to which surety paper is exposed.
A bank note thus printed in TWO PERMANENT INKS, would be protected against the possibility of imitation by photography, and by the lithographic and anastatic processes of copying; while its denominational value could not be altered by any chemical means. Such a note could also be made to unite the security afforded by the highest artistic excellence, against counterfeiting by the engraving process; and the beauty of design and general appearance of the note would be preserved.
The GREEN COLOURED INK, recently patented, has been submitted to the examination of several of our most distinguished chemists, and other gentlemen, who, from their practical experience, are competent to decide a question of this kind. They have subjected it to the most severe tests known to chemical science; and the ink having been pronounced by them to possess the requisite properties, we offer it, with entire confidence, as affording the desired protection when applied in the manner above proposed.
Referring to the accompanying documents, and specimen of printing in the two permanent inks, we are,
Your obedient servants,
Rawdon, Wright, Hatch & Edson.
Early banknote printing