Editing Counterfeit banknote detection pen (section)

====False positives====

The effectiveness of the pens may be affected by external methods.  Simply having a banknote pass through laundry, depending on the soaps and bleaches used, can cause a bill to fail the test when it is otherwise accepted. Additionally, it was discovered that treating a counterfeit note with a dilute solution of [[vitamin C]] will cause a false negative: that is, it will respond to the iodine-based ink as though it were made of the same paper as a valid banknote.<ref>{{cite web|title=How do Counterfeit Pen Tests Work?|date=20 July 2017|work=Banknote World Resource Hub|author=Abdullah Beydoun |url=https://www.banknoteworld.com/resource-hub/portfolio/how-do-counterfeit-pen-tests-work/}}</ref>