Scams / Science / Skepticism · September 5, 2006

Testing the Counterfeit Money Detector Pen by DriMark

Crooks have been copying money ever since its invention. Ancient gold coins were faked by filling them with lead; counterfeits as simple as a slug were used to defeat older vending machines; and these days fake money is made using printing presses or laser printers.

The ability to detect counterfeit bills is a valuable skill to learn by anyone who handles money on a regular basis. To encourage this skill the Secret Service prints a pamphlet called Know Your Money (viewable online) that describes how to detect counterfeit bills. The guide assumes that the person receiving a bill will pay attention to the details of the bill. Of course experience also helps; sometimes a counterfeit bill just doesn’t ‘feel’ or ‘look’ right.

Machines also exist that will assist in sorting legitimate bills from fake, but these machines are not perfect. The best detection of counterfeit money is still a person who is familiar with currency and pays attention.

And then there is the Counterfeit Money Detector Pen.

This pen, made and patented by DriMark Products, seems to instantly determine the validity of paper currency using a process that is mysterious to most users. A cashier merely marks a bill with this pen, and if the mark is yellowish, amber or clear then the currency is valid. If the mark turns dark brown or black then the currency is phony.

Cashiers take great comfort in this patented process. I’ve seen clerks at the local corner market use these pens on ten-dollar bills. I’ve seen cashiers at my credit union use these pens to check hundred dollar bills. And I’ve noticed that in all cases that when the pen is used the attendant instantly trusts the results.

Let me restate that. It is possible that an inexperienced cashier, or one who is in a hurry, will accept counterfeit money as authentic if it passes the ‘pen test,’ even if that currency would clearly be detectable as counterfeit to another person who took the time to examine it. Most cashiers seem to have a blind faith in these pens.

How does the pen work?

As I mentioned, this pen is patented. The patent number is 5,063,163 , and can be seen online at the United States Patent and Trademark Office. According to the patent claims, this pen contains a testing solution comprised of one of several different chemical recipes. The active ingredient is Iodine, and the remainder is one of several solvents.

The patent claims that this solution will detect, “…illegitimate paper currency by detecting the starch content therein in excess of the genuine currency.” It does this using a known reaction between Iodine and starch, called an ‘Iodine Test’.

The Iodine Test is a standard chemical method of detecting starch. Simply stated Iodine reacts with starch to produce a deep blue-black color. (Here is another link for those interested in the chemistry of the Iodine Test.) The test solution in the DriMark pen is naturally a light golden-brown or yellowish color, but when mixed with starch the color changes dramatically to a dark black.

One of the ways that the United States Mint has tried to combat counterfeited bills is to use distinctive paper. Standard paper, like the kind used in a copy machine, is composed of wood cellulose bound together with starch-based glue. Paper used in currency is composed of cotton or linen fabric that has been beaten and cooked to create fine fibers. The process causes the fibers to interlock naturally without the requirement of a starch binding material which makes for a very strong, high quality paper. Paper used for United States currency has other additions, such as tiny red and blue fibers and a plastic / metallic strip embedded in it. Due to the method of manufacture, paper currency will not disintegrate or weaken substantially when wet.

There is very little, if any, starch in American currency.

James Randi has tried to tell people that these pens give a false sense of comfort to those who trust them over all other means of counterfeit detection. He hasn’t had much success in his attempt at education, and I can sympathize. I have also tried to explain to my credit union tellers that they should learn how to use their senses to discover counterfeits. I’m still trying, patiently, to educate.

Mr. Randi isn’t as patient as I am, so to make his point he sometimes withdraws money from his bank, coats it with spray starch, and then returns it. (Presumably he banks at a higher quality establishment than I do, because his tellers don’t seem to check the bills with a counterfeit detector pen.)

Skeptical testing of spray starch on money

I love to read James Randi’s weekly Swift Commentary because I learn so much from him. Perhaps the biggest lesson I’ve taken from Randi and other skeptics is that as a skeptic I’m NOT required to blindly believe what they say. I’m allowed and encouraged to find competing opinions, do my own research, or even perform my own experiments. So in this vein I decided to run my own experiment on the counterfeit detection pen.

My questions:

  1. Will DriMark’s Counterfeit Detection Pen respond properly to paper currency and standard computer paper?
  2. Is there another sort of paper that would be detected as ‘currency’ by the pen?
  3. Randi coats money with spray starch to fool the pen – does that work?
  4. If I find a non-currency paper that fools the pen, can I spray it with starch so that it will then read as ‘counterfeit’?
  5. I’ve read that hairspray would defeat the pen and cause it to indicate non-currency paper is valid currency. Is this true? Can I cause starch-soaked currency to read as valid?


  1. DriMark Counterfeit Detector Pen with adhesive holder! (It was cheaper than purchasing 3 to a package.) Patent number 5,063,163 is proudly printed on the bottom of the package.
  2. Dollar bills. I used four singles instead of twenties, fifties or hundreds for two reasons. First, I’ll be writing on these bills with a counterfeit detection pen, and I don’t want a cashier to refuse my money because they think it’s funny. Second, I’m not so rich that I can play with hundred dollar bills!
  3. Starch. I could have used a powder starch and mixed it with water, but who needs that hassle? I used Niagara spray starch because I’m familiar with it from using it every week for ten years while I was in the Air Force.
  4. Hair Spray. After a lot of thought I made the scientific decision to use Suave unscented with Extra Hold. (Luckily I happened to have a supply of this in my bathroom!)
  5. Computer paper, coffee filters, paper towels. Other sorts of paper to experiment on, and to use to clean up my mess afterwards.
  6. One domestic felines, absolutely required as an impartial observer and judge. My feline owner, a Mr. Samuel Francisco, (aka Cisco) was gracious enough to volunteer his services.


  1. Test the pen to make sure it can tell the difference between good money and computer paper. This initial check also serves to prove that the pen is working as advertised. I applied the pen to one of the dollar bills and to a sheet of computer paper (folded in half).
  2. Apply spray starch to the next dollar bill in an attempt to make it read as fake. Apply hairspray to the folded computer paper in an attempt to make it read as real. I used an evaporative rotary oscillator to facilitate in the drying of these sprays.
  3. After drying, test the results by re-applying the counterfeit money detector pen to both the dollar and to the computer paper.
  4. Using the counterfeit money detector pen, test a single coffee filter paper from the package of Brew Rite bargain filters that I found in my cupboard.
  5. Spray another coffee filter paper with starch and allow to dry on the evaporative rotary oscillator.
  6. Using the counterfeit money detector pen, test the coffee filter sprayed with starch to determine if it registers as counterfeit or real.
  7. Using the dollar bill sprayed with starch from item (2) above, spray this bill with hairspray and allow it to dry.
  8. Test the bill with the counterfeit money detector pen to determine if it registers as fake or real.

(Left) Testing the coffee filter

Evaporative Rotary
Not every lab has such high tech equipment!


  1. Writing on money is legal as long as I don’t make it ‘unfit for circulation’ according to title 18, Section 333 of the United States Code. Still I find myself reluctant to write on it, so helpfully I write, “Not Fake” to put any receiving cashiers at ease. Writing on computer paper is easy except I have a minor bit of writer’s block, so I just give a friendly ‘Hi!’ The pen works as expected – the computer paper is fake money, and the dollar bill is real money.
  2. After spraying the bill with starch and the computer paper with hairspray I again test them both with the counterfeit detector pen. As predicted by James Randi, the second dollar bill now reads as counterfeit. The pen now indicates that the hairsprayed computer paper is genuine currency.
  3. I then tested a coffee filter with the counterfeit pen. The coffee filter is apparently made completely out of genuine American currency paper because the pen indicates that it is NOT counterfeit.
  4. I sprayed a new coffee filter with starch and allowed it to dry on the evaporator. Afterwards I tested it with the counterfeit detector pen and found that the coffee filter now (correctly) reads as counterfeit paper. I have no idea what starch will do to my morning cup of coffee, but I’ll bet it isn’t anything good!
  5. At this point my neutral feline observer decided to preform a randoml quality control inspection while I worked, so I very carefully sprayed the previously starched bill with hair spray under his scrutiny.
  6. The starched dollar bill, sprayed with hairspray, is now very shiny in the camera flash, but obviously NOT a counterfeit!

(Note that I used the word ‘skeptic’ with a comforting smily face on the dollar bill instead of the word ‘fake’ or ‘counterfeit’. No sense in making cashiers nervous!)

Here is a bill that was sprayed with starch, then with hairspray. It ‘failed’ and registered as counterfeit after being sprayed with starch, and then it ‘passed’ and registers as real money after being sprayed with hairspray.

This treatment results in a bill that has become ‘slick’ in feel, and somewhat glossy in photos.

The ‘Skeptic’ and smily face became a bit smeared after the application of hair spray. Perhaps I used a bit much?

Mr. Samuel Francisco inspects the experiment and gives it his qualified approval before demanding his payment in tinned cubed chicken bits.


  • During this test I accidentally marked one of the paper towels with the counterfeit detector pen, and found out that it was also apparently composed of genuine currency. I did not test these paper towels with starch or hairspray because I learned during cleanup that the starch made them very soggy.
  • At first I used the spray on, rub dry method of drying the dollar bills after applying starch, but the first bill I tried this on indicated as ‘not counterfeit’ after rubbing with a paper towel. It is my assumption that I didn’t allow enough time for the starch to soak into the bill. All further bills were allowed to dry without interference. The rubbed bill was removed from the experiment.


As you can see from the pictures, under normal circumstances the counterfeit detector pen is able to tell the difference between computer paper and currency. It is NOT able to tell the difference between coffee filters and real money. (Or paper towels either.)

The counterfeit detector pen will indicate that money sprayed with starch is counterfeit. This is due to the reaction between the iodine in the pen and the starch on the paper. The computer paper sprayed with hairspray is detected as genuine currency because the hairspray creates a barrier between the iodine in the pen and the starch that is used as a binding agent in the paper.

Some types of paper do not contain starch as a binding agent. Since starch is dissolvable in water, I guess it would be bad for coffee filters or paper towels to be held together with something that would cause them to fall apart during their normal usage. It may also be possible that starch would adversely affect the quality of coffee if it were added during the coffee-making process.

Adding starch to coffee filter paper makes it register as counterfeit because the iodine in the detector pen reacts to the added starch.

A dollar bill coated with starch and then sprayed with hair spray will be detected as genuine currency by the pen due to the hairspray barrier between the iodine in the pen and the starch on the bill.

As a side affect, spraying bills with starch makes them feel a little more ‘slick’ to my fingers. Spraying them with hairspray makes them feel more ‘fuzzy’. Under a camera flash they become very reflective, but look normal under regular lighting.


A few weeks ago I made the mistake of leaving my wallet in my pants, which then went through the wash. Luckily I don’t use starch in my wash anymore. (I did when I was in the military.) If you do use starch in your wash, and happen to wash an extra twenty, fifty or hundred dollar bill in your pocket, then you are in danger of having that bill flagged as ‘counterfeit’ by DriMark’s pen. Luckily, you can make your bill ‘good’ again by merely spraying it with hairspray!

Counterfeiters who use a laser printer to print fake bills on computer paper could make all their bills acceptable to cashiers who rely on DriMark’s pen by adding a coating of hairspray.

In my opinion, counterfeit money detection pens are a scam because DriMark can overcharge the user for inexpensive iodine. The price of these pens is much higher than the price of an equivalent amount of iodine.

I purchased this pen for $4 from Office Depot. According to the patent, the counterfeit detector pen is composed of 0.5 to 2.0% iodine. An eight ounce bottle of 10% iodine solution is $12 from Walgreens. If diluted to the proper consistency I predict that the bottle of iodine will be in use long after four DriMark pens have evaporated to uselessness.

I believe that counterfeit money detection pens are a dangerous scam due to the blind faith that most cashiers have in their ability to detect phony money. Counterfeiters who take the time to create funny money will certainly take the time to defeat these pens. I would guess that counterfeiters actively look for cashiers who rely on these pens because these cashiers are an ‘easy target’ for disposing of fake bills.