Editing Counterfeit banknote detection pen (section)

==Background==
[[Counterfeit money|Counterfeit banknote]] detection pens are used to detect [[counterfeit]] [[Swiss franc]], [[euro]] and [[Federal Reserve Note|United States banknotes]], amongst others. Typically, genuine banknotes are printed on paper based on cotton fibers and do not contain the starches that are reactive with iodine. When the pen is used to mark genuine bills, the mark is yellowish or colourless.

Such pens are most effective against counterfeit notes printed on a standard printer or [[photocopier]] paper.<ref>{{cite web|url= http://money.howstuffworks.com/question212.htm |title=How does a counterfeit detector pen work? 123  | work=HowStuffWorks |date=April 2000 |accessdate= 2008-03-28}}</ref> The chemical properties of US banknotes printed before 1960 make marking pens useless, resulting in [[false positives and false negatives|false positives]].<ref>{{cite web
  |url= http://www.coinbooks.org/esylum_v10n50a25.html
  |title= OLD PAPER MONEY AND COUNTERFEIT-DETECTING PENS
  |publisher= The E-Sylum
  |date= December 9, 2007
}}</ref> One example of this complication taking place happened in 2016, in which a 13-year-old student was arrested by police after she attempted to pay for lunch with a red seal Series 1953 [[United States two-dollar bill|$2 bill]] after the school's counterfeit pen was unable to prove its authenticity.<ref>{{cite web | url=http://abc13.com/news/lunchroom-lunacy-isd-cops-investigate-fake-money/1314203/ | title=Lunchroom Lunacy: ISD cops investigate $2 bill spent on school lunch | date=29 April 2016 | publisher=abc13.com | accessdate=Jul 15, 2019}}</ref>