Counterfeit pen
From Wikipedia, the free encyclopedia
Counterfeit pens are pens containing an iodine-based ink. They can be used to detect counterfeit Swiss, Euro and United States banknotes amongst others. Typically, genuine banknotes are printed on paper based on cotton fibers, and do not contain the starches that react with iodine. When the pen is used to mark genuine bills, the mark is yellowish or clear.
Counterfeit notes, however, are often printed on the commonly used wood pulp based paper. The iodine in the ink reacts to starch in the wood pulp, and the pen makes a dark mark indicating a counterfeit note.
Pen manufactures claim over 98% effectiveness[1], but critics suggest the effectiveness is only around 80% for new bills, and lower for older bills.[2] Magician James Randi has given lectures stating that counterfeit pens are not effective. He also has written about their usage on his website's weekly commentaries.
Some counterfeiters bleach small denominations and print more valuable bills on the blank paper to evade this test.
