Marked Playing Cards Technology
Card marking is the practice of altering a deck of playing cards in some way that allows for different methods for cheating and magic tricks. It can be done by a variety of means, from simple crimps and bends to adding invisible marks or other changes. It is most commonly used by card sharps and by magicians to perform their tricks. Casinos also use some methods to detect card marking in order to prevent cheating.
The first known marking techniques date back to the 14th century when poker cards appeared and became popular. Early ways to mark cards included bending, crimping and pinprick bumps. Later, other methods began to appear including cut-out work and shade techniques. Shade marking involves changing the back design of a card and is the most deceptive method. It works by adding or removing small elements in the pattern, bolding the lines and changing the color. This technique requires special tools and expert knowledge.
Other methods include luminous or juice marked cards. These are marked using a chemical that reacts with a specific light wavelength. They can then be seen by a reader device such as contact lenses or gimmicked sunglasses. This type of marking can be very difficult to detect and is often the choice of magicians.
Phoenix playing cards are an example of this type of marked cards. They are punched through the backs so that they can be riffled and can also have hidden markings in the back patterns.