In 1929, when the United States Bureau of Engraving and Printing introduced the small-size note, that we currently use today, green pigment was readily available in large quantities. The color was relatively resistant to physical and chemical changes, and the color was viewed to be psychologically identified with the security and strength of the United States Government.
More importantly, this newly developed ink had protective qualities that could not be easily “lifted” from the note itself, which had been a favorite technique of counterfeiters in the past. Since the mid-1800’s, it had been customary to print bills in black, with different slight variants of color. When photographed, the color variants would show only in black, since early cameras could only photograph in black. Not to be outdone, the counterfeiter soon discovered that they could remove the colored elements from the Bill, photograph the remaining black ink elements, make copies, and then overprint an imitation of the colored parts on the newly made copies.
A new solution was needed, and was quickly developed. The development, as well as the patent purchase for this ink, was by Tracy R. Edson, who later Founded the American Banknote Company, one of the same firms that produced the first currency used by the United States.
The faces of these early notes that were produced under contract were printed with the newly patented green tinted protective ink.
When printing with oil-base type inks, like the new “patent green,” it is not unusual for the color to show through to the opposite side of the sheet. Therefore, the backs of early notes were printed in a darker shade of green to make the “strike through” of the tint less obvious.
The transition to the Treasury Department’s Bureau of Engraving and Printing was gradual, so the backs of the notes produced there during the intervening period were continued to be printed in green for the sake of uniformity.
Once the Bureau was in full-scale production, there was no reason to change the traditional color, and it was only logical that the practice continue.
Thus, the “greenback” was born!
The Bureau currently uses a technique called “Intaglio Printing,” which involves a revolving plate, filled with the grooves containing the design and wording. These grooves are filled with ink and then wiped clean on the surface. The paper is forced with approximately 20 tons of pressure onto the plate, picking up the ink contained within the finely recessed lines and grooves, leaving the surface of the newly printed currency with a slightly “raised” feel, while the reverse has a slightly indented feel.
Thanks to new technology introduced in the last few years, the newly redesigned, recently introduced United States Currency features some new splashes of color on the various denominations, using an “Optically Variable Ink” (or OVI). This ink allows a shift in color variation when held at different angles.
A copy machine, for example, scans a document at ONE FIXED ANGLE, relative to the bill’s angle when placed on the glass, thus not picking up the color shift.
This ink, produced by a Swiss company called SIPCA, is not readily available and thus aids in deferring counterfeiting.
So, the next time you reach in your wallet and pull out a Greenback, you’ll know why it’s green!