cheating playing cards from Salem are originated from cards marking. the card marking is a process of changing the playing card in a manner that is obvious to the marker or conspirator, for example by bending or adding a visible mark to a card, either by punching holes through the middle of cards or trimming their edges, or cutting-out, using a razor to scrape off some of the printed areas of the card, such as adding (cutting out) a white bird to the back design.
this allows different methods of card sharpness to poker cheat or can be used for magic. to be effective in , one or more distinct markers must be seen on the front side of the card, and these markers are generally uniform. by looking back, this kind of initial cards marking deck from is rough and foolish; we can see the mark apparently. it's hard to ignore. and its biggest shortage is that it can't mark the whole deck of cards.Read More
Invisible ink from , also known as security ink, is a substance used for writing, which is invisible either on application or soon thereafter, and can later be made visible by some means. invisible ink is one form of steganography. says wiki. invisible ink playing cards are kind of senior marked cards that using marked cards printer to print unified marking on the back, including cards suits and value.
around 600 ad, and in the 16th century in europe, lemons were used by arabs as organic inks from . this is the first time that lemon juice used as invisible ink to hide some secret information. but this lemon juice can't mark on the playing cards, the effect is not stable. then until last 90s century, the technical of marking cards with invisible ink is getting mature.
At the beginning, people invented invisible ink pen to mark cards. They make any marks only they know on the back of the playing cards, to indicate the cards value. At this time, the effect of this invisible ink is better than the lemon juice, but is still not stable enough. The hidden marks is too strong that easy to reveal, or too light to see clearly.
then, with the development of science and technology, people invented the marked cards printer from . the invisible marks made by marked cards printer are card values that fused to the pattern of the card's back, incorporated into the back image so that they do not attract attention when fleeting, and it will not dull the finish of the cards and that it works on both paper and 100% plastic playing cards from .
No long later, people improved the invisible ink and the Printing Technology. They can make a barcode marks, like the QR code, on the four edges of the playing cards. It's called barcode marked cards. You can't see the cards' values and suits of each card directly. It needs to use with poker analyzer and scanner camera. Once the dealer shuffles and deal the barcode card to the players, the infrared scanner camera will read the invisible “barcode” printed on the card, the analyzer processes the data, and sends a voice message to the spy microphone. All analyzers are needed to set the number of players, it can be done by remote control as well.
When you order a pack of marked cards, it is shipped with its seal and plastic wrap “intact,” This makes the other players less suspicious, as the pack can be opened in front of their eyes.