Creating the die
All paper money begins with the making a steel master die, based upon the denomination. These must be carved by engravers working on the steel plates. The changing of the person in the office of the Secretary of Treasury or the Treasurer of the United States is accompanied by a new master die being cut. The signature of the new officeholder is expanded on a copy sheet. An engraver then replicates the design using a special pen. The engraver's movements are mirrored by a machine which matches the engraver's motions and cuts the signature into the die.
The master die creates the printing plates
The master die must be replicated in order to be able to print sheets of money rather than a single bill at a time. A plastic sheet is placed over the die and heated to get the raised impressions from the die. This is done a total of 32 times. These plastic sheets are then attached together to form a 4-by-8 sheet, known as an alto. Each sheet of 32 (alto) is then dipped into a tank where copper is electroplated to the surface in a recessed image of the plastic's raised design. The plastic alto is then removed and the copper basso is sent for inspection. If there are no flaws, it is covered in chromium to harden it. Now it is a master printing plate.
Creating the substrate
Each piece of U.S. paper currency is a combination of 75 percent cotton with 25 percent linen. This blank paper currency is known as a substrate. A security thread is inserted between two sheets to allow it to be seen when held to the light. The paper is cut to the same size as the master printing plate to make sheets which will allow for 32 individual bills on each.
The intaglio printing process
Stacks of 10,000 of these substrates are fed into a hopper on the printing line. The master plate is attached to a printing cylinder. Ink covers the master printing plate, and the extra is wiped off, leaving only the ink in the recesses of the printing plate. Each sheet is pressed between the plate and an impression cylinder. The 15,000 psi of pressure exerted forces the ink in the recess onto the bill. The result is that the ink is slightly raised above the surface of the bill. It takes one hour for the printing press to print one side of the 10,000 sheets fed into the hopper of the machine. The back green color is printed first before allowing to dry for up to 48 hours, and then the front black ink is printed onto the bills.
Serial numbers and the colored printing
Two dried stacks of 10,000 printed bills are fed into the next press. This letterhead press, imprints the color seal of the Treasury and the black serial numbers. The numbers are printed so that once the stacks are completed, the bills will be in sequential order. The finished bills inspected. Should a defect be found, the bill is marked to be removed after cutting, and a bill with the same serial number and a * at the end will be put into its place. These are known as "star notes".
Cutting, stacking, wrapping, and shipping
The completed sheets of bills are stacked 100 high and cut into individual stacks with a blade that cuts straight down through the sheets. Bills marked to be replaced with the star notes are taken out and the star notes put in their place. This keeps the sequential order of the bills. Each stack of 100 bills gets a paper wrapper. A final visual inspection is given before these stacks are then compiled into a bundle of 10. These bundles are then shrinkwrapped together in groups of 4 known as "bricks". These bricks are then shipped to the Federal Reserve agencies and other federal money distribution sites.