Answer
May 20, 2025 - 06:25 AM
A counterfeit detection pen typically contains an iodine-based ink that reacts with the starch in wood-based paper. If the currency is fake, the pen mark will turn a dark color, usually brown or black, indicating the presence of starch. Genuine currency paper, which is made from cotton and linen fibers, does not react with the pen, so the mark remains clear or turns a light amber color.
