Step-by-step, here's how a new batch of $1 bills is made

Although cash may seem old-fashioned, it is still a relevant form of currency. This is especially true as digital currencies make headlines and Treasury Secretary Janet Yellen is fielding questions about ideas to mint a $1 trillion platinum coin to avert a debt-ceiling crisis.

In many parts of the world, cash is still the primary form of payment.

In December, Yellen made history on a trip to the Bureau of Engraving and Printing in Fort Worth, Texas. There, she signed commemorative notes at the unveiling of a batch of dollar bills.

This was the first occasion that U.S. banknotes, which have been signed by 29 previous Treasury secretaries, featured the signature of a female Treasury secretary.

The nation's currency was remade on one of the rare occasions. Here is an in-depth look at how it is done.

The new design for the bill, including the new signature, is printed onto metal.

A team of experienced designers and engravers are needed to etch the plates with portraits, vignettes, lettering and ornamentation in order to make money. The designs are crafted with both aesthetics and security in mind.

A tool called a pantograph has been used for more than a century to scale engravings so they can fit on working plates and be printed in smaller sizes on notes exchanged around the world.

A currency redesign can take many years, except when a new Treasury secretary takes over. The new signature is usually added in a matter of months, beginning with a ceremonial signing that is captured digitally and engraved onto the metal plates that are the primary building blocks for printing the bills.

The signature of the secretary can be hard to read sometimes.

In December, Yellen joked that the founding fathers did not account for the 'terrible handwriting' of the nation's Treasury secretaries. She acknowledged that she had practiced her penmanship.

The technicians use the etchings to construct the plates that will transfer the images to paper.

Printing presses require a set of three to four metal plates, which can take up to eight days to produce. The images are transferred to the plates using steel dies, which are essentially giant cookie cutters. Then, the plates must be cleaned and polished.

After the plates are inspected, they receive a chrome coating that makes them hard enough to withstand the 65-ton force of the printing press, which transfers the images from the plates to the paper.

There are several steps. The back of the notes are printed first, then inspected for quality. Then the front is printed.

The bills are printed with a mix of black and color-shifting ink or metallic ink to avoid counterfeiting. The ink is a special blend developed by the Bureau of Engraving and Printing to avoid counterfeiting.

The paper is a mix of linen and cotton and red and blue fibers that are interspersed to further complicate attempts to make fake bills. Different notes also have specific security features, such as watermarks and threads.

For most denominations, high-speed offset printers that can print 10,000 sheets per hour are used to layer on the base coat colors. The more intricate details are done with intaglio printing, a process where ink is applied to the engravings and transferred with immense pressure to paper. In the case of $1 and $2 bills, offset printing is not used, and intaglio printing is the first step.

Throughout the process, quality control checks happen. Inspectors make sure that the ink is properly transferring to the paper without any unwanted smears or smudges.

The bill-front printing cannot begin until the plates have been inspected for imperfections yet again, cleaned, and polished. No detail is too small: Even a missing feather on the American bald eagle must be corrected.

The signature of the Treasury secretary, on the bottom-right corner of each bill, must also be inspected.

Sheets of currency begin to roll off the presses.

Bills are inspected using magnifying glasses and high-tech computer systems.

Operators who work with presses pull sheets of currency frequently to inspect the paper for defects and to make sure that the colors and designs are correctly aligned.

The signature of the Treasury secretary must be checked again to ensure that it is free of smudges and perfectly legible.

An advanced computer system that uses cameras and software inspects uncut sheets of currency to ensure quality control of large quantities of notes. Problematic sheets are transferred to another inspection system that allows for good notes to be preserved and the rest to be destroyed.

The finishing touches, like serial numbers, are applied and the sheets are cut to the correct size.

The machines allow for the currency to be printed, inspected, cut, and packaged more quickly.

The final layer of printing is the letterpress process. At this stage, two green serial numbers and four Federal Reserve Bank designation numbers are added.

The final step in the process is to affix the seals of the Federal Reserve and the Treasury Department to the currency notes.

Bills that have been printed are wrapped up in stacks and then sent to the Federal Reserve.

They are divided into "straps" of 100 notes held together with a white paper band that is color coded and says the denomination. Those are then piled into bundles and combined to form a "brick," which is then shrink-wrapped.

Bricks containing 16,000 notes each are loaded together in groups of four to make a 'cash pack.' From there, they are distributed into the banking system.

The central bank has not yet announced when the new currency will be released.

This article was originally published in

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