The Treasury Department does not produce the paper used to print money. The paper’s manufacture is contracted out to a private company better known for business stationery: Crane and Company of Dalton, Massachusetts. The type of currency paper now used, with the red and blue fibers, was developed by the Treasury Department in conjunction with Crane and Company. It has been in use since 1879.
Officially, the formulation of the paper is a secret. In fact, however, there is very little that isn’t known about the paper. Every counterfeiter since 1879 has tried to duplicate it, with varying degrees of success. From time to time, curious paper chemists have broken it down and surmised its salient features. It’s known, for instance, that the paper is 75 percent cotton and 25 percent linen. (Originally it was 100 percent linen, then 75 percent, and then 50 percent.) It is permeated with red and blue fibers. U.S. currency has three hidden security features:
1. The paper fluoresces under an ultraviolet lamp.
2. The ink is magnetic—not to a degree you could notice with a pocket magnet, but enough to be detected with special machines.
3. The paper is riddled with tiny, invisible holes. Under a microscope, pinpoints of light shine through. (Many counterfeit papers are solid.)
Money used to be made from used clothing. Crane purchased old cotton shirts, hired ragpickers to remove the buttons, and bleached the fabric white. Now most shirts contain polyester, and the dyes don’t bleach out. “New rag cuttings”—small squares of virgin fabric—rather than old shirts are the principal raw material of money today. Crane buys them from textile firms.
The first step in the production of any rag paper is to convert the rag into pulp. The cuttings of cotton and linen (in a three-to-one ratio) are mixed with water—probably just about enough to cover the cloth—and beaten in large machines. Hours later, the mixture is a uniform pulp with no fibers remaining.
The blue and red fibers must be added at this stage. If they were added during the beating, the colored fibers would likewise be reduced to pulp. Examination of the finished currency paper reveals that the fibers are embedded in the paper, not just pasted onto its surface. Therefore they must be mixed into the pulp before the sheets are formed.
The pulp is poured into molds. Paper molds usually consist of a wooden frame with a fine wire mesh bottom. They are somewhat larger than the dry, finished sheets to allow for shrinkage. The pulp must be spread evenly in the mold, and the amount of pulp must be gauged to a final dry-sheet thickness in the range of 0.0042 to 0.0045 inch.
Excess water drips through the wire mesh, leaving a newly formed sheet in the mold. The damp sheets are probably “couched” as most fine paper is—carefully transferred to wool mats or “felts.” The sheets and felts are sandwiched together and squeezed in a press to remove further water.
The next step is loft drying, to which currency paper owes much of its durability. The sheets are peeled from the felts and placed on a large screen, the loft, to dry. The faster paper dries, the stronger it becomes; the loft allows it to dry from both sides at once.
Paper to be used for printing must be “sized.” Sizing prevents the ink from soaking in and spreading out. If you tried to write on a paper towel (an unsized paper) with a fountain pen, the ink would feather and the writing become illegible. Currency paper, then, obviously is well sized to take the fine engraving. The best sizing material, and the one that paper chemists agree is used for
U.S. currency, is glue. Glue sizing is actually a gelatin made by boiling the hoofs, ears, and other unused parts of slaughtered livestock. It is sold in a dry, flaky form and dissolved in water to yield a thin sizing bath. Dry sheets are immersed in the bath, removed, pressed, and dried.
The exceptional uniformity of currency paper betrays the final step in its manufacture. No matter how carefully the pulp is spread in the molds, even thickness is impossible to ensure without plate finishing. In this step the sheets are sandwiched between polished metal plates. Heavy rollers compress the sandwiched sheets under great pressure. Although mere lagniappe, this finishing is nearly impossible to duplicate with makeshift equipment. High-pressure rollers are expensive machines. (In contrast, all the steps up to plate finishing can be duplicated by amateur paper-makers at home.) The thickness of counterfeit paper usually varies outside the Treasury Department tolerances.
The finished sheets are cut to measure 53.5 by 63.0 centimeters—-just enough for thirty-two bills, eight down and four across.