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February 1, 2007

How to detect counterfeit currency with a refrigerator magnet


Great hack from Cy Tymony's piece in Make magazine, Volume 7.

Here's what he wrote:

"Legitimate [U.S.] currency has iron particles in the ink. Fold a bill so half of it stands up vertically — if the top edge moves toward your magnet, it's the real deal. If not, phone the Secret Service!"

I sent my crack research team out back to our skunk works to check this out.

You know how skeptical we are around here.

But I digress.

Sure enough, Tymony's tip is spot-on.

But in order to shorten your learning curve (I realize how busy you are), let me note that the fridge magnet will demonstrate its attractive effect only within approximately 1/8" (2-3mm) of the bill.

So just holding up a magnet and expecting a bill in someone's bag or wallet across the room to explode out is asking a bit much.

Also — the effect is not demonstrable if there is an appreciable air current in the vicinity.

Do not attempt this maneuver on a windy hilltop and then say I'm so wrong.

Attempt it in a nice quiet room, then say it.

February 1, 2007 at 12:01 PM | Permalink


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How did the counterfeit currency do? And how much of that do you have?

Posted by: Mike Beversluis | Feb 1, 2007 3:44:56 PM

Joe I think you are wrong.

Send me a crisp $100 bill, and I'll show you.

Posted by: clifyt | Feb 1, 2007 2:37:58 PM

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