How Do Counterfeit Detection Pens Work?
Counterfeit currency detection pens use chemical color indicators to sense trace chemicals left in the paper from the manufacturing process. Most governments use special paper manufacturing processes that to not leave the same trace chemicals residues. Starch and iodate salts seem to be the most common trace chemical residue tested for in commercial paper. Counterfeit pens contain an iodine based ink. Genuine banknotes are printed on paper based on cotton fibers and do not contain the starches that react with iodine. Counterfeit notes are often printed on the commonly used wood pulp based paper and the iodine in the ink reacts to starch in the wood pulp and the pen makes a dark mark indicating a counterfeit note. With the counterfeit detection pen, test mark any area of a bill. Wait one second. If a dark brown or black mark appears, the bill is a suspected counterfeit. If a gold or yellow mark appears, the bill is good. This yellow mark will fade away in a few days. A black mark remain
