How Paper Money Is Made
How paper money is made today at the
U.S. Bureau of Engraving and Printing
Since 2003, new designs for denominations of $5‑$100 include security features to make these bills more difficult to counterfeit.
The production of modern U.S. paper money is a complex procedure involving highly trained and skilled craftspeople, specialized equipment, and a combination of time-honored printing techniques merged with sophisticated, cutting edge technology. Recent new designs for denominations of $5-$100 use similar portraits and historical images to previous notes, but include subtle background colors to make the bills more difficult to counterfeit. Security features include a portrait watermark visible when held up to the light, two numeric watermarks on $5 notes, enhanced security thread that glows under an ultraviolet light, micro printing, color-shifting ink that changes color when the note is tilted, and a 3-D security ribbon on the new $100 bills.
Paper and Ink
While most paper used for such items as newspapers and books is primarily made of wood pulp, the currency paper made specifically for the Bureau of Engraving and Printing (BEP) is composed of 75% cotton and 25% linen – with the security thread and watermark built in. All U.S. paper money features green ink on the backs, while the faces use black ink, color-shifting ink in the lower right corner of $10-$100 notes, and metallic ink for the freedom icons on $10, $20 and $50 bills. The "bell in the inkwell" freedom icon on $100 notes uses color-shifting ink.
For notes of $5 and above with subtle background colors, offset printing is the first stage of production. The colored background design is duplicated on a film negative, and is transferred to a thin steel printing plate with light-sensitive coating through exposure to ultraviolet light. This is called "burning a plate". The background colors are then printed on the BEP's Simultan presses, which are state-of-the-art, high-speed rotary presses. Ink is transferred from the printing plates to rubber "blanket" cylinders, which then transfer the ink to the paper as it passes through the blankets. The printed sheets are dried for 72 hours before continuing.
Intaglio printing is used for the portraits, vignettes, scrollwork, numerals and lettering unique to each denomination. From an Italian word meaning to cut or engrave, "intaglio" refers to the design being skillfully "carved" into steel dies with sharp tools and acids. Some engravers specialize in portraits and vignettes, while others are experts in lettering and script. The images are then combined and transferred to a printing plate through the process of siderography. Engraved plates are mounted on the press and covered with ink, a wiper removes the excess ink, and ink is left only in the recessed image area. Paper is laid atop the plate, and when pressed together, ink from the recessed areas of the plate is pulled onto the paper to create the finished image.
The green engraving on the back of U.S. currency is printed on high-speed, sheet-fed rotary intaglio presses. Back-printed sheets require 72 hours to dry and cure before moving to the face intaglio press, where special cut-out ink rollers transfer different inks to specific portions of the engraved designs. Black ink is used for the border, portrait and Treasury signatures, color-shifting ink for lower right portions of $10 and higher-denomination notes, metallic ink for freedom icons on $10, $20 and $50 bills, and color-shifting ink for the freedom icon on $100 notes.
UOCIS Inspection System
The BEP's Upgraded Offline Currency Inspection System (UOCIS) integrates computers, cameras and sophisticated software to thoroughly analyze and evaluate untrimmed printed sheets. This system ensures proper color registration and ink density, and within 3/10 of a second determines whether a sheet is acceptable or must be rejected. The same equipment trims and cuts the 32-subject sheets in half to create two 16-subject sheets. The sheets then move to the final printing stage accomplished by the BEP's Currency Overprinting Processing Equipment and Packaging (COPE-Pak).
The letters on a modern serial number from the color series represent the series year, the Federal Reserve Bank to which the note was issued, and a counting device.
The star indicates this sheet replaces one found defective.
An uncut sheet of 32 $1 bills
COPE-Pak adds the two serial numbers, black Federal Reserve seal, green Treasury seal, and Federal Reserve identification numbers. Modern serial numbers consist of two prefix letters, eight numerals, and one suffix letter. The first prefix number indicates the series (for example, Series 1999 is designated by the letter B). The second prefix letter indicates the Federal Reserve Bank to which the note was issued. The suffix letter changes every 99,999,999 notes (DG99999999A is followed by DG00000001B).
As sheets pass through the process, they are inspected by the COPE Vision Inspection System (CVIS). If a sheet is identified as defective, it is replaced with a "star" sheet. Serial numbers of notes on star sheets are identical to the notes they replaced, except that a star appears after the serial number in place of the suffix number.
Completed currency sheets are stacked and pass through two guillotine cutters. The first horizontal cut leaves the notes in pairs, while the second vertical cut produces individual finished notes. Bricks of 4,000 notes are shrink-wrapped for delivery to the Federal Reserve System.