Security Features in U.S. Paper Currency
It’s not enough for money to simply serve its basic function as legal tender, it’s also got to be smart—and increasingly so. Each time bills are redesigned they gain security features that make them more and more difficult to reproduce, and while U.S. paper currency has its fair share of detractors, there are some pretty awesome design elements at work when it comes to what’s in our wallets.
Paper money isn’t actually paper at all—at 75 percent cotton and 25 percent linen, it’s essentially fabric, making it much more durable than actual paper would be. It takes about 4000 double folds before a bill will tear.
A single company has provided the paper for U.S. bills since 1879—Crane & Co. in Dalton, Mass. The company has a storied place in U.S. history. In 1776, it was called Liberty Paper Mill, and serviced Paul Revere when he needed to print notes for paying American Revolution soldiers.
Finally, "greenbacks" they may be, but embedded throughout Federal Reserve Notes are tiny red and blue fibers. Counterfeiters often try to simulate these by printing tiny red and blue lines on the paper.
In a $5, $10, $20, or $50 bill, the paper contains a security thread and a watermark. To see them, you have to hold the note to the light, and the placement and style are different for each bill. The security thread glows a specific color when exposed to ultraviolet light.
The $100 bill also has a wider, 3D holographic blue security ribbon woven into the paper to the right of Franklin’s portrait. If you tilt the note back and forth you can see the bells change to 100s, and move side to side. This feature adds a highly advanced level of security that’s difficult to simulate.
The redesigned $10, $20, $50, and $100 bills go through several stages of printing in order to create the finished notes. Each bill is printed four times on three different kinds of printing machinery. All bills utilize green ink on the backs, but faces use black, color-shifting, metallic ink, and other inks which are specially formulated and blended by the Bureau of Engraving and Printing.
In 2003, with the introduction of the redesigned $20s, subtle background colors were added to the currency to enhance the security. For these denominations, offset printing is the first printing that occurs on the “blank” paper. They’re printed using the BEP's Simultan presses, which are over 50 feet long and weigh over 70 tons. They're capable of printing 10,000 sheets per hour, and operators will regularly examine sheets to make sure the colors are remaining constant.