If you have seen a card magician perform at the amusement park or in a circus troupe, you may have noticed that he seems to have a special skill in picking out a specific card from a shuffled deck. In fact, it is not his magical powers, but a result of the magic decks he uses that have invisible marks on them.
Invisible markings are a very useful technique in poker cheating, and they can be used to mark cards in ways that human eyes cannot detect. Usually, these invisible ink markers are applied to the back of the cards. They are then read by a special device that allows the player to decode the markings and know the number and suit of his opponent’s cards before they are dealt.
Historically, invisible ink was something that intelligence agencies like the CIA and MI6 used to conceal secret messages. Substances such as vitriol, vinegar and lemon juice were materials used to conceal these messages, which could then be revealed through a range of means including heat or adding different chemicals.
As technology progresses, invisible marking techniques become more sophisticated. The newest way to mark cards is to use invisible ink that can only be seen deep into the infrared spectrum. This is read by a hidden camera which then relays the results to a player’s earpiece. This type of marked cards is being used by some poker sites, including Ultimate Bet and Absolute Poker.