Paper Money

NPR interviews developer of $100 blue security thread

The blue security thread used on current generation $100 Federal Reserve notes was the subject of a recent report on National Public Radio.

Image courtesy of Vladimir Buravlev.

The blue security thread that has been one of the distinguishing features of $100 Federal Reserve notes since the series of 2009 is the byproduct of a new graduate’s response to an online help-wanted ad, says an Oct. 23 report about anti-counterfeiting measures on National Public Radio by Allyson McCabe.

The position advertised was for a director of research and development for Crane Currency. The man who answered the ad and got the job was Sam Cape. He became responsible for the thread’s refinement into a finished product. At his first interview, he was shown a prototype of the thread and, he says, it “blew his mind.”

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It looked like film, but was three-dimensional and simulated movement. His job would be to improve it, refine it, and incorporate this “visual illusion,” which he compared to some of the gift cards that used to be in Cracker Jack boxes, into Crane’s bank note paper. Cape says the thread is made of microscopic lenses so small that a dozen of them would fit on a tip of human hair. There are close to a million of them on each $100 bill.

The blue strip has bells that change to 100s as the note is tilted. It is woven into the paper rather than printed and was initially so difficult to handle that it is said to be the cause of the paper creasing that delayed the issue of the Series 2009 $100 notes. 

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The note also bears a color-shifting image of a bell within an inkwell that shifts color from copper to green when the bill is tilted. 

Compared to the $1 to $20 Federal Reserve notes, which cost from about 5.4 cents each to 12.2 cents each, the $100 note is relatively expensive to produce at 15.5 cents each (the $50 note, however, costs 19.4 cents each to produce).

Cape argues that, despite all the innovations, one of the best security features is also one of the oldest — the combination of the raised printing and Crane’s venerable 75 percent cotton, 25 percent linen paper. He also states that this paper is more difficult to obtain than the plastics that go into polymer currency.

The Bureau of Engraving and Printing’s director, Len Olijar, added that less than one-hundredth of 1 percent of U.S. paper money in circulation is counterfeit. He attributed this to robust security features, some of which are not apparent, not always disclosed, and are meant to be noticed by machines rather than the human eye.

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