Scheduled Maintenance: Our website will be unavailable starting Friday, April 10 at 5:00 PM CST and will be back online Monday, April 13 at 6:00 AM CST. We appreciate your patience.
Just place a mark anywhere on the suspect bill. If the mark stays amber, the bill is genuine U.S. currency; if the mark turns black, the money may be counterfeit. Ordinary paper contains starch while U.S. currency paper does not. The pen “ink” contains an iodine–potassium iodide solution that when combined with starch, produces a characteristic blue complex.