[roadcat]

The pens essentially only work if an idiot makes a counterfeit bill.

No. They may work on older genuine bills. See my post#26.

[ltc8k6]

Bills can also get starch on them in various innocent ways. They get washed in the laundry a lot.

You can take a bill, spray it lightly with laundry starch, and watch it fail the pen test.