How to Tell if a $100 Bill is Real With a Marker

The circulation of counterfeit currency poses a challenge to financial systems and individuals alike. To combat this, counterfeit detection markers have become a widely used tool, particularly for verifying the authenticity of $100 bills. Understanding how these markers work and utilizing other embedded security features can help protect against accepting fraudulent currency.

How Counterfeit Detection Markers Work

Counterfeit detection markers operate on a basic chemical principle involving iodine.

Genuine United States currency is printed on a unique paper blend of 75% cotton and 25% linen, which contains no starch. In contrast, most common paper, such as that used in household printers, is wood-based and contains starch. When the iodine solution in a detection marker comes into contact with starch, a chemical reaction occurs. This reaction causes the mark to turn a dark brown or black color. If the marker is applied to genuine currency paper, which lacks starch, the iodine will not react, and the mark will remain clear or pale yellow.

Using the Marker and Interpreting Results

To use a counterfeit detection marker, draw a small line on an inconspicuous area of the $100 bill, such as the blank border. After applying the mark, observe the color change within a few seconds. If the mark stays clear or turns a pale yellow, the bill is likely genuine.

However, if the mark turns dark brown or black, it indicates the presence of starch in the paper, suggesting the bill is likely counterfeit. These markers are not foolproof. Some counterfeits can bypass the marker test, leading to false positives or negatives.

Essential Security Features Beyond the Marker

Relying solely on a counterfeit detection marker is insufficient for thorough verification, as the $100 bill incorporates multiple advanced security features.

• A portrait watermark of Benjamin Franklin appears as a faint image in the blank space to the right of the portrait when held to light, visible from both sides.
• A security thread, embedded vertically to the left of Benjamin Franklin’s portrait, reveals alternating “USA” and “100” text when held to light and glows pink under ultraviolet light.
• Color-shifting ink on the numeral “100” in the lower right corner and on the bell in the inkwell changes color from copper to green when the bill is tilted.
• Microprinting, tiny text requiring magnification, is on Franklin’s jacket collar and around the portrait watermark.
• Raised printing, or intaglio printing, provides a distinctive tactile feel on certain areas, such as Franklin’s shoulder.
• Genuine currency paper contains small, randomly distributed red and blue fibers visible to the naked eye.

What to Do If You Suspect a Counterfeit

If you suspect you have received a counterfeit $100 bill, handle it carefully to preserve evidence. Do not return the bill to the person who passed it to you. Limit handling the bill as much as possible, placing it in an envelope or protective cover.

Try to remember details about the passer’s physical appearance and any vehicle information, such as a license plate number. Contact your local police department or the nearest United States Secret Service field office to report the suspected counterfeit. Knowingly passing a counterfeit bill is illegal, even if you received it unknowingly.