Counterfeit Corner

Why do so many shops rely on the counterfeit detection pen to authenticate their paper banknotes?

First, let us look at how the pen works.

The pen contains a liquid iodine solution that is a yellow-orange colour. When this solution comes into contact with starch, it turns dark blue/black. Genuine paper banknotes do not contain starch, whereas regular copy paper does. The solution is absorbed into the paper and reacts with the paper, not the inks. If a genuine banknote is marked with the pen, it should leave a faint yellow colour. The pen will leave a black mark on an uncoated paper counterfeit.

However, there are several problems with this method of authentication.

1.A genuine banknote may pick up starch during circulation, for example if it is washed in a detergent containing starch, or has absorbed grease from food. In this scenario, the genuine banknote is assumed to be counterfeit and refused.

2.A counterfeiter may use starch free paper to produce the counterfeit, such as resumé paper. Many counterfeiters will invest in the more expensive paper to avoid a positive pen test from retailers.

3.A counterfeiter may coat the surface of the counterfeit to prevent the iodine solution reaching the paper containing starch. Deodorant, hairspray, and varnish are a few of the products that have been known to work. Opening an evidence bag containing counterfeit banknotes and a waft of perfume enveloping your senses may indicate that a coating was applied to prevent the pen test from working.

4.The counterfeiter may use a technique called bleaching to produce the counterfeit banknote. This process involves removing most/all the ink from a genuine banknote (usually a low denomination) and printing a higher denomination on the blank genuine paper. This is commonly seen in countries where all the denominations are the same size. Remember, the pen is detecting the paper, and in this case the paper is genuine!

Examining the security features present on the banknote is the best way to authenticate them!

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