Why the Counterfeit Marker Pens Don't Work

Everybody has seen it at least once or twice. Many of you may have even done it yourselves as you run the cash register in your business. A customer pays his bill with a large denomination banknote, and the cashier takes out that old-fashioned pen marker and checks the bill to see if it is fake or not. Unfortunately, the days of the marker pen being a useful test for counterfeit notes are behind us.

The OLD pH testing pen

There are, generally speaking, two “types” of counterfeit marker pen testers. The older devices (dating back 20 or more years, but still available today) are a simple type of pH tester. Frank Abagnale, whose life as a con artist and then a law enforcement agent was portrayed in the movie "Catch Me If You Can", explains that the pH testing method is crude, “the pen merely checks the pH level of the bill. Since U.S. currency-paper has a high pH, a bill with a low pH will be revealed as a fake. But that doesn't mean any bill that passes the test is authentic. Office Depot has thousands of (paper) stocks with high pH," he says. "This can only capture the rank amateur." How true it is. Police officers in the Financial Fraud department of the LAPD tell us that there have been cases where a criminal will go to an office supply company, buy a currency marker pen, then go through printing-paper stocks with the pen testing each type until they find one that tests positive. They then buy that paper stock, and go home to their “printing labs” to produce photocopy counterfeits that can pass the pen test.

The NEWER (but still ineffective) Chemical Testing Pens

Faced with the reality that the pH tester pens were quickly losing effectiveness, the makers developed 2 new types of pen that utilize different tests. The newer pens look to react with chemicals that either 1) should be found in US banknote paper (in this case, calcium) or 2) that should NOT be in the paper (Starch). When a fake bill is encountered, the indicator fluid in the pen will turn black. Unfortunately for the maker of the calcium tester pen, the counterfeiters were busy testing countermeasures almost immediately after it was released, and it was soon discovered that several commonly available household items would do the trick. According to Sam Tong, assistant special agent in charge of the Secret Service, Honolulu office in February 2004, “Spray starch or hair spray applied to deceptive [currency] can confound a counterfeit-seeking marker pen.” He also said that older genuine currency without the special calcium compound will falsely test as “fake” with these pens.

The problem with the starch-detection pens is that the inventor assumed counterfeiters would use cheap paper to print their product. Cheap paper contains starch — as "sizing" so that the paper looks brighter and will be more easily handled by printing machines. According to the patent papers filed for the “Smart Money Counterfeit Detector Pen” a pen filled with tincture of iodine will reveal phony money because starch turns black in contact with iodine. So, as with the pH testing pen, the simple trick to fooling this pen is to test the paper and choose a printing stock that does not use starch sizing.


While it would be nice to believe that a $5.95 marker pen can protect us from counterfeit currency, the reality is that countermeasures to all of the available marker testing pens have long been developed and understood, and can be easily researched on the internet by anybody who is aspiring to become a counterfeiter. Midwest Fraud Prevention’s line of products provides a higher level of technical complexity that has not been “counter-measured” by the criminals. In many cases, the same devices that test currency notes may also be used to verify driver licenses, passports and other I.D. documents, as well as traveler checks, money orders and a variety of other negotiable instruments and important documents.


©2009, Midwest Fraud Prevention