Many businesses where I shop will routinely swipe some kind of felt-tip marker across the paper of the bill. So there is some kind of chemistry test, too.
Yep. Ordinary paper is wood pulp with a starch sizing, the iodine in that felt tip will stain it purple.
Banknote paper is actually a thin felt, mostly cotton fibers, with a protein sizing.
I’m told there are a number of synthetic odors added to the bills. These are ones that humans lack receptors for, but dogs can smell.
That beagle at the airport? He’s not just sniffing for bombs, he’s also looking for currency being smuggled out of the country...
“Many businesses where I shop will routinely swipe some kind of felt-tip marker across the paper of the bill. So there is some kind of chemistry test, too.”
I’m not positive, but I believe that the reason the color changes is due to the ink being absorbed into the paper before it eventually fades.
I worked as a cashier at Home Depot and noticed that if you take a recipt with one glossy side and one regular feeling paper side, and mark both sides with the counterfit pen than the glossy side stays yellow (good) and the regular feeling side turns black (bad).