What Color Does the Marker Turn on a Fake Bill?

Counterfeit currency poses a persistent challenge for businesses and individuals. Counterfeit detection markers offer a common initial defense against these deceptive notes. These pens provide a quick assessment tool during everyday transactions.

How Counterfeit Detection Markers Work

Counterfeit detection markers employ a chemical reaction to distinguish between genuine and fraudulent paper currency. These pens contain an iodine-based solution designed to react specifically with starch. Genuine U.S. currency paper is starch-free, made from a blend of cotton and linen fibers, unlike wood pulp paper which contains starch.

When the iodine solution from the pen is applied to a genuine bill, it remains clear or turns a faint, quick-fading yellow or amber color. Most common paper types used in counterfeiting, such as standard printer or photocopy paper, are wood-pulp based and contain starch. When the pen’s solution comes into contact with starch in these counterfeit papers, a distinct chemical reaction occurs.

This reaction causes the mark to turn a dark brown, black, or dark blue color. The dark color indicates the presence of starch, signaling that the bill is likely a counterfeit. This visible color change provides a straightforward and rapid indicator for counterfeit currency during a transaction.

Limitations of the Marker

While counterfeit detection markers are useful for identifying basic counterfeits, they are not foolproof. These pens solely test for the presence of starch in the paper. This means they may not detect more sophisticated counterfeit bills that are produced on paper without starch, or on paper that closely resembles genuine currency.

One common method used by counterfeiters to bypass these pens involves bleaching the ink off lower-denomination genuine bills and then reprinting them as higher denominations. Since the underlying paper is genuine, the marker will indicate the bill as authentic, even though it is a counterfeit. Additionally, some counterfeiters might treat their paper with chemicals, such as a vitamin C solution, to prevent the starch-iodine reaction, leading to a false positive. The effectiveness of the solution within the pen can also degrade over time, leading to inaccurate results.

Additional Ways to Identify Counterfeit Currency

Given the limitations of detection pens, a multi-point inspection of currency is recommended to ensure authenticity. One method involves feeling the paper; genuine U.S. currency has a distinct, slightly rough texture from intaglio printing, which is difficult for counterfeiters to replicate.

Holding the bill to a light source reveals several security features. A faint watermark, typically matching the portrait on the bill, should be visible from both sides. Additionally, a security thread is embedded vertically within the paper, imprinted with text indicating the bill’s denomination. This thread also glows a specific color under ultraviolet (UV) light, which varies by denomination.

Tilting the bill can reveal color-shifting ink on denominations $10 and higher, where the numeral in the lower right corner changes color. The $100 bill also features a 3-D security ribbon woven into the paper, with images of bells and “100s” that appear to move when the bill is tilted. Examining the microprinting, tiny text requiring magnification, provides another layer of security, as this is challenging for counterfeiters to replicate. Genuine U.S. currency paper contains small red and blue fibers embedded randomly throughout, which are part of the paper itself, unlike those merely printed on a counterfeit.