The note incorporates several safety features whose efficacy federal agents will monitor carefully during the next few years. Yet, at the same time, any security-enhancing feature added to currency must also be acceptable technologically and politically to society. This requires a delicate balance. Although it considered printing the bills on plastics, synthetics, high-tech cloth, and other materials, the interagency committee ultimately advised the treasury to stick with the traditional paper, a blend of 75 percent cotton and 25 percent linen. In the intaglio process long used for Uncle Sam's greenbacks, hand-crafted plates that press ink onto paper give each note a distinctive embossed texture.
Intaglio images remain crisp for a long time before fading.
Moreover, since intaglio requires millions of dollars of machinery and great finesse, the process remains quite difficult to replicate. From a materials standpoint, even surviving the intaglio printing process puts the substrate through a rigorous test. We print 8,000 sheets per hour under enormous pressures, thousands of pounds per square inch. In the end, the currency features must remain recognizable after a lot of abuse. Multicolored inks, a decorative feature of much European currency, didn't pass muster with the NRC committee.