With much trouble flowing around with counterfeit money, the United States tried enhancing the physical features of the American paper currency, making it harder to duplicate. In 1990, security threads and microprinting were introduced and put into production for the Series 1990 $100, $50 Federal Reserve notes, and by the end of the 1993 series all of denominations were changed except $1 and $2 notes. A security threads is a “clear, inscribed polyester thread” (Anatomy of a Bill: The Currency Paper) that run on the width of the paper currency printed with its own denomination; for example, a $50 note would say “USA 50” repeatedly throughout the thread. Depending on the denomination, the locations in which the security threads run vary on the paper currency. In order to see the security thread, the paper currency should be transmitted through light and when exposed to ultraviolet light, glows red. What cannot be recreated easily by advanced copiers and printers, microprinting can only be seen through magnification. In 1990, the words “The United States of America” were micropinted around the edges of the portraits on the notes.
Cited: Fun Facts About Money. Federal Reserve Bank of San Francisco, 1996. Web. 24 Nov. 2009. . History of Currency Designs. USPaperMoney.Info, Oct. 2000. Web. 23 Nov. 2009. KNOW YOUR MONEY and Federal Reserve Seal. USA.gov, 2008. Web. 02 Nov. 2009. . Ross, Kelley L. Six Kinds of United States Paper Currency. Kelley L. Ross, Ph.D., 1979. Web. 24 Nov The Redesigned Currency. The Department of the Treasury Bureau of Engraving and Printing. 2009