Card marking has been around since playing cards were invented. Card magic is used by magicians and cheats to perform card tricks. It’s not illegal to mark cards in gambling games or private home games, but it is a form of cheating and can ruin the experience for others.
There are several ways to mark cards. The most common are: juice-marking, tintwork (using a tint that can only be detected by certain filtered glasses), and daubing. Some hustlers also use the abrasion techniques, which can be done with a fingernail or a tip of a thumb.
While it is generally considered wrong to mark cards for a social gathering, some card magicians feel that it is a legitimate trickery tool. Boris Wild is a magician who uses marked cards constantly because it allows him to practice different techniques for reading the cards. This makes his tricks more convincing.
While a marked deck can look suspicious, it’s important to remember that it’s only a problem when the mark is actually visible to spectators. Most card markings don’t show up and are only noticed by judges during a deck-check in a sanctioned event. When a judge examines a deck, they look for warping, crimps and discoloration, as well as card thickness. If any of these are present, the deck is flagged.