In order to see through playing cards, you need to wear infrared glasses or contact lenses. They can detect invisible marks on the back of the cards, letting you know the type of card you are dealing. These marked cards are used in magic shows and poker.
The mark is usually created with a special ink that is invisible to the naked eye but can be seen with a specialized light source or a deck of special infrared marked cards. This type of card marking is very popular with magicians because it allows them to read a set of cards without any other players knowing that a secret code has been applied to the cards.
There are other ways to mark cards, like using a paint or daub that only reacts to a certain wavelength. This type of marking is done with a special shade known as two-way shade. This shading is usually done by hand with a small amount of colorant.
This type of shading can be difficult to detect even by the most experienced poker player. This type is often used by professional magicians. If you want to play a trick that relies on card marking, it is best to practice the trick with a regular deck of cards first. This way, you can make sure that no one on the table is able to detect any cheating.