Why were the U.S. paper currency bills redesigned? Nova explains in Nova: Secrets of Making Money that the project was undertaken primarily for security reasons. The original bills were too easy to counterfeit and procedures for doing so are demonstrated. New features to thwart would-be counterfeiters in the 100 dollar bill include a watermark, a bigger portrait, microprinting, and color-shifting ink. Also shown is the torture tests bills must go through to pass muster. The Treasury Department subjects them to washing, exposure to sun, gasoline, drying, and crumpling.
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