# Special markers/pens to scrawl on $100 bills to check for counterfeits? **URL:** \ **Category:** Factual Questions\ **Created:** [January 4, 2015, 10:33pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984 "2015-01-04T22:33:13Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 4, 2015, 10:33pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/1 "2015-01-04T22:33:13Z")
I got a crispy new bizarrely-un-Green new $100 bill from the bank, used it the only place I could (Whole Foods, NYC) and the cashier wrote some big squiggles on it. I thought she was marking it kosher-for-Whole Foods or something, but she was just smooshing it around, and said the ink–on the bill?–from the pen?–would run if it was a phony. Anyone ever heard of this? ---
**Author:** ![tanstaafl](https://avatars.discourse-cdn.com/v4/letter/t/ba8739/32.png) [@tanstaafl](https://boards.straightdope.com/u/tanstaafl)\ **Post date:** [January 4, 2015, 10:41pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/2 "2015-01-04T22:41:44Z")
Haven’t heard of “run”; most pens cause counterfeits to turn black. [How counterfeit detection pens work](http://money.howstuffworks.com/question212.htm) ---
**Author:** ![Procrustus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/procrustus/32/2994_2.png) [@Procrustus](https://boards.straightdope.com/u/Procrustus)\ **Post date:** [January 4, 2015, 10:55pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/3 "2015-01-04T22:55:55Z")
I see such pens often at casinos, probably for obvious reasons. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [January 4, 2015, 11:16pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/4 "2015-01-04T23:16:45Z")
Thanks to all. ---
**Author:** ![grude](https://avatars.discourse-cdn.com/v4/letter/g/e47774/32.png) [@grude](https://boards.straightdope.com/u/grude)\ **Post date:** [January 4, 2015, 11:27pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/5 "2015-01-04T23:27:50Z")
Huh? Are you saying she wrote on it with a regular marker, and then tried to smudge the ink to see if it was a fake? Counterfeit detection pens are iodine, not regular ink. And every time I have seen one used the cashier just does a little dot or small line to see if it turns black, not squiggle all over it. ---
**Author:** ![Cardboard](https://avatars.discourse-cdn.com/v4/letter/c/49beb7/32.png) [@Cardboard](https://boards.straightdope.com/u/Cardboard)\ **Post date:** [January 4, 2015, 11:31pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/6 "2015-01-04T23:31:14Z")
I have one of those pens. You can buy them at Wal-Mart. If you ever want to write a super secret temporary message, they’re the pen to use. The ink turns dark on regular paper, but fades to nothing (or almost nothing) over time. ---
**Author:** ![xythenz](https://avatars.discourse-cdn.com/v4/letter/x/a88e57/32.png) [@xythenz](https://boards.straightdope.com/u/xythenz)\ **Post date:** [January 5, 2015, 12:10am UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/7 "2015-01-05T00:10:44Z")
I worked as a cashier and had those markers but nobody ever explained what it was suppose to do . Its noticable when you compare the results on paper and regular bills. With the markers we had, on real bills it would fade out a bit to a transparent light brown or green. On paper it was extremely dark. I use to draw mustaches on all the bills to see if my bills ever circulated back to me. If you ever come across an extremely detailed mustached on a 50 or 100 dollar bill with a little dot in the eye it was probably me. I actually managed to get a few back before the ink completely faded. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [January 5, 2015, 12:46am UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/8 "2015-01-05T00:46:17Z")
Those markers are not very reliable to use I’m afraid. > **[Counterfeit banknote detection pen](https://en.wikipedia.org/wiki/Counterfeit_banknote_detection_pen)** > > A counterfeit banknote detection pen is a pen used to apply an iodine-based ink to banknotes in an attempt to determine their authenticity. The ink reacts with starch in wood-based paper to create a black or blue mark but the paper in a real bill contains no starch, so the pen mark remains unchanged. > Counterfeit banknote detection pens are used to detect counterfeit Swiss franc, euro and United States banknotes, amongst others. Typically, genuine banknotes are printed on paper based on cotton fi... > [@](#): > > Critics suggest the effectiveness is much lower. Critics claim that professional counterfeiters use starch-free paper, making the pen unable to detect the majority of counterfeit money in circulation.[3] Magician and skeptic James Randi has written about the ineffectiveness of counterfeit pens on numerous occasions[4][5] and uses a pen as an example during his lectures.[6] Randi claims to have contacted a United States Secret Service inspector and asked whether the pen works as advertised, to which the inspector replied “it is not dependable.”[4] The Secret Service does not include such pens in their guidelines for the public’s detection of counterfeit US currency.[7] ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [January 5, 2015, 12:35pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/9 "2015-01-05T12:35:13Z")
See [Bloomberg - Are you a robot?](http://www.bloomberg.com/news/2014-05-07/mom-with-hp-printer-shows-the-digital-ease-of-bogus-cash.html) Bloomberg article says that the test of the absorption property or starch test would probably work, because probably the printing was done on (wood) paper… well based on statistics, thats the most common way for the USA based forger to work… simple photocopier (or laser jet or inkjet print… ) For better protection, use a strong magnifier, eg jewelers eye piece, to inspect fine print, and security devices. Worn out notes may be refused, don’t skip the security tests on worn notes, if they are obviously old or mistreated, then just refuse them for that reason. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [January 5, 2015, 12:58pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/10 "2015-01-05T12:58:27Z")
We have those pens at my work but I don’t train my cashiers to use them. All they do is check to make sure that the bill is printed on the proper type of paper (or rather, that it’s not printed on the wrong type of paper). But all a counterfeiter has to do is bleach a bill use that to print their money on (say, bleach a five dollar bill and print a fifty over it) and the marker will say it’s good. That’s fooled a few of my cashiers over the years. My cashiers are trained to hold the higher denomination bills up to the light and actually read the wording on the strip that runs through the bill. The counterfeiter plans on a cashier holding the bill up and just seeing the strip and watermark and assuming it’s a good bill (and it looks like it is), but if you have a fifty and the strip says “USA 5 USA 5 USA 5” instead of “USA 50”…which is an absolute PITA to read then you have a bad bill. But I’ve yet to have a bill with the proper strip in that the bank didn’t accept. ---
**Author:** ![california\_jobcase](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@california\_jobcase](https://boards.straightdope.com/u/california_jobcase)\ **Post date:** [January 5, 2015, 2:26pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/11 "2015-01-05T14:26:26Z")
I used to iron and starch one-dollar bills when I had a bunch I knew I was going to feed to vending machines. I have wondered what troubles might ensue if I paid a friend with cash I had treated with spray starch. What would an astute cashier do if the pen darkened, but the other security measures were clearly present? ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [January 5, 2015, 5:00pm UTC](https://boards.straightdope.com/t/special-markers-pens-to-scrawl-on-100-bills-to-check-for-counterfeits/708984/12 "2015-01-05T17:00:57Z")
Just for fun, I’ve spray-starched a few $50 and $100 bills. If it fails the pen-test, they sometimes will scrutinize it more, but I only had one refused once. That one time, I used a starched $50 bill to try to pay for fast food. The manager gave me the meal for free instead of risking giving me the meal _and_ $43 in change. I think the pen is a really bad idea. A good counterfeit wouldn’t be printed on printer paper, and for the crappy counterfeits that are, just teaching your cashier to recognize the actual protection measures built into the bill is more effective.