How to See Through Playing Cards

In the past, card players have used many methods to cheat at poker. This includes secretly marking cards. This is done usually by scratching or smudging a card, or by bending it. Only those who are playing the game will be able to see the mark. Some of these markings are so subtle that even an experienced eye cannot detect them. Others are more elaborate, involving special invisible ink or sophisticated electronic poker cheating devices that look like they were taken from a James Bond movie.

A deck can be premarked prior to the beginning of a game with “juice” (or “daub”) or “daub”. This ink is visible deep into the IR spectrum and can be read remotely by a cheating device to determine a card’s suit and value. This information is transmitted to the player through a hidden earpiece.

Another way to mark the cards is with a sequence IR-absorbing spots. When illuminated with IR, these spots of IR-absorbing ink appear on the card as dark areas, as shown in the image. These images are then scanned by a camera, which can determine the card’s rank and suit.

To make the marks appear more convincing, it’s best to begin in the petal closest to the suit of the cards. For example: a Club would be in the first petal. Hearts would be in the second. Spades in third. Diamonds in fourth. Repeat the marks on each card’s opposite side so that they can be seen whichever way the opponent holds it.