Often times, store employees do not know how to identify counterfeit bills and rely on the simplest, least reliable counterfeit detection tool: the counterfeit pen. As a result, multiple fake bills are accepted in cash registers; this causes financial losses because those bills are worth nothing when attempting to deposit them at the bank. Here is the thing, counterfeit pens will not detect any fake bills other than some amateur counterfeits printed with a basic laser printer on regular paper, so beware.
So, how does a counterfeit pen really work and how can it tell if a bill is fake or not? It is pretty simple; real bills are printed on cotton fiber paper and do not contain the starches (contained in regular white printer paper) that react with iodine. Therefore, when a bill is genuine, the pen will leave a colorless or brownish mark; if however the bill is counterfeit and printed on regular paper, the pen will detect the starch and its mark will turn black.
The reason why this type of counterfeit detector is not reliable is because it is extremely simple for counterfeiters to replicate bills on the cotton fiber paper used to print real currency. They can either get a genuine dollar bill, bleach it and use it to print a higher denomination, or a less common way is to get their hands on actual currency paper provided by foreign governments unfriendly to the U.S.
There are much better, affordable alternatives to a counterfeit pen in order to put a barrier to counterfeits while saving time and minimizing human error; many types of higher technology counterfeit detectors are available for purchase with features able to recognize most of the security elements included in large denomination bills. From ultraviolet light to magnetic thread detection, manual to automatic detection, a fake note detector is an investment that always gives a great return for your business (it can pay for itself by only detecting one, two or three fake hundred dollar bills depending on the level of sophistication of the machine).