Intaglio printing is what gives the U.S. currency its distinctive look. The process begins with an engraving, both of the portrait and of the fine line detail surrounding the bill. This beautiful art is painstakingly produced by a master engraver on steel plates. These master plates form the actual production plates used during the printing process. A high-viscosity ink is then applied to the plates, and the printing process begins. The plates are first wiped clean, leaving only ink in the grooves, then pressed with enormous pressure (7,500 to 15,000 psi) which transfers the ink to the paper. The enormous pressure causes the paper to be embossed with the ink, thus giving the ink a distinctive raised feel that other printing techniques cannot duplicate. The very fine engravings appear muddy when reproduced in counterfeit notes. While most of the front and back part of the bill is produced in this way, the Treasury seal, Federal Reserve seal and serial numbers are not printed with the Intaglio process.
The portrait may not seem to be a security feature, but the Treasury maintains that the face is the most recognizable part of money. People will tend to remember faces, and if the bill is counterfeit, they will see that the face is not exactly right. As people already associated Ben Franklin with the $100 bill, the Treasury did not want to change the face on the bill. While the faces on some foreign currency change as the countries political climate changes, the U.S wanted to present an image of stability. Instead, they decided to enlarge the portrait on the new $100. The portrait was painstakingly engraved by Thomas Hipschen, and the Treasury hopes the new enlarged details will make counterfeit bills stand out more clearly from the real thing. By moving the portrait to the left, the face will suffer less wear from folding. The move also makes extra room for the watermark on the right side.
Color Shifting Ink
Perhaps the most «high-tech» of the new security features, the black to green color-shifting is a new and important element of the redesigned $100 bill. Similar types of ink have already been used on some foreign currency and on the newest U.S. passports. The change in color is the result of multi-layered metallic flakes added to the ink. When the bill is tilted, light reflects off these flakes at different wavelengths and changes colors. This is called color diffraction, which is also responsible for the color variations found on the wings of some butterflies. Because this special combination of materials and ink is sold exclusively to the United States government, the Treasury is hopeful that this will be one feature that will be extremely difficult to counterfeit.
Microprinting appears as just a thin line to the naked eye, but can be easily read upon magnification. The introduction of microprinting in 1990 began with the addition of the words «The United States of America» printed around the edge of the portraits. The new bills still use microprinting, but in a different location. These words now appear around Ben Franklin’s lapel. In addition, the words «USA 100» are printed within the lower left «100.» Microprinting is very difficult to reproduce accurately on photocopiers because most copiers do not have the ability to work at such high resolution. This situation may not last long, however, as improved scanning devices are now able to print at this fine detailed level. The Treasury hopes the combination of the many anti-replication features will help deter potential counterfeiters.
Fine Line Engraving
Fine circular lines appear around the portrait of the bill. The clarity and detail of these lines are difficult for scanners and photocopiers to reproduce. These lines often cause a blur, or moiré, during the scanning process.
Serial Numbers and Treasury Seal
The serial number is especially important for banks which handle large amounts of cash. No two serial numbers are the same. On the new bills, these serial numbers have been increased to 11 digits. In addition, the new bills contain a redesigned Federal Reserve seal and code which indicate the bill’s issuing bank. While the old bills contain this information, on the new bills the numbers are clearer and easier to identify. The old green Treasury seal hidden behind the «100» has long been part of U.S currency and will remain an important security feature. This detailed combination of green and black is difficult to reproduce. Like all overt features, however, the new bills will require continuous upgrades and additions as new technology arises that makes the features more vulnerable.
Currency paper has a unique feel and is extremely durable. Is it really ‘paper’ in the traditional sense? There are no wood fibers or starch in currency paper. Instead, like high quality stationery, currency paper is composed of a special blend of cotton and linen fibers. The strength comes from raw materials continuously refined until the special feel of the currency is achieved. People who handle money on a regular basis, such as bank tellers, can easily determine if a bill is counterfeit by this distinctive feel. The characteristic yellowish-green tint of U.S. currency is another distinctive feature which is, in fact, hard for color photocopiers to accurately match.
Red and Blue Fibers
Red and blue fibers have been a longtime ingredient of U.S. currency paper. Special features like these fibers are embedded in currency paper to ensure that reproduction is difficult. While some counterfeiters attempt to draw these fibers onto the surface of the bill, close inspection reveals the absence of the authentic embedded fiber and the clear presence of crude lines drawn on the surface.
Security threads, which now run the width of the currency, are not a new invention. In some early versions of paper currency, thin security threads were added to paper. In these currencies, the number of threads in the paper represented a specific denomination. Security threads help prevent counterfeiters from raising notes — bleaching out the paper of a low denomination and printing a higher denomination onto the authentic paper. The new threads were first added to U.S. currency in 1990 and have recently been improved. In the redesigned notes, a security thread will appear in a different location depending on the denomination. The thread for the new $100 bill carries the words «USA 100» and can only be seen with transmitted light, which makes photocopying impossible. In addition, the new security threads glow red when held over ultraviolet light.
For the 1996 series a watermark was added to the paper. This is also not a new invention. Watermarks were first used in the late thirteenth century in the handmade papers of Italy. They have long been used to mark important documents, and have appeared on a variety of foreign currency. Watermarks can also be found as part of any high quality stationery. Even Ben Franklin’s stationery had its own personal watermark. The watermark is created during the paper making process and is caused by variations in the density of the paper. As light passes through these tiny variations in thickness, it creates different tones. When held up to transmitted light these varying tones form a clear image — and in the case of the new $100, a second image of Ben Franklin.