Cards marking

Card marking is the process of altering playing cards in a method only apparent to marker or conspirator, such as by bending or adding visible marks to a card. This allows different methods for card sharps to cheat or may be used for magic tricks. To be effective, the distinguishing mark or marks must be visible on the obverse sides of the cards, which are normally uniform.

Casinos alter playing cards used at table games before they are sold or given away to prevent cheaters from buying them to cheat at table games.

Card marking is often used to cheat when gambling or for card tricks. Many casinos, particularly those in Las Vegas alter the decks of cards they sell to tourists – either by punching holes through the middle of cards or trimming their edges – to prevent cheaters from returning to the game tables after buying the cards and then slipping the favorable cards into their hands when playing.

Marked cards can be used regardless of who shuffles and deals the cards. Some more sophisticated marked-cards scams involve additional manipulative skills to steer the cards into the correct positions once the desired cards have been identified.

Luminous marked cards - These can only be read by using special gimmicked sunglasses or by wearing contact lenses. The original luminous systems used red lenses and greenish ink on the back of red cards. New luminous technology, called Ultra-Luminous, uses more sophisticated techniques that are based upon chemical and optical scientific principles different from the original luminous systems.

Video-luminous marked cards - Video-luminous cards use marks that can not be seen by the human eye, even through a luminous filter. The marks can only be read by using custom-designed electronics and filters and displayed on a TV monitor in another room to a partner. Then the card values may be signaled or transmitted to the player who needs to know. Video-luminous does not have to be used for cheating. They may be used for magic or by a poker house or person who may want to analyze a card game after the fact. If collusion is suspected, the recorded images of the marked cards may be played back later to detect any unusual play. If a player consistently folds a good hand when a partner plays a better hand, then it can be assumed that collusion is taking place in the game. Since these marks cannot be seen by the human eye, there is no chance of detection of the marks, even by knowledgeable players, during the game. Often such marked decks will only be introduced by the house when suspected colluders are seated.

Juice-marked cards - The marks are only visible when a person is trained to read the marks. No filtered sunglasses are required, but some practice is required to read the marks. Glasses can be used to make it easier to spot these marks.

Tintwork or shade - This technique uses a tint solution to mark cards, but the marking patterns vary depending upon the back design of the cards being marked.

Daub - A special paste is used by a player to mark someone else's deck, on the fly, while the cards are being used during a game and even while being watched. This eliminates the need to switch in a pre-marked deck of cards.

Juice dust - An advanced type of daub, it may be used to make an ad hoc juiced deck. Like daub, it also allows a player to mark someone else's deck, on the fly, while being watched. The main advantages of juice dust are that it will not dull the finish of the cards and that it works on both paper and 100% plastic playing cards.