There are many articles online that describe how easy it can be to mark cards. It’s harder to cheat in a casino. There are still ways for cheaters to mark cards and remain undetected.
The most common way to do this is to color a small section of the back of the card at strategic places. Other methods include scuffing with a small amount paint or using a luminescent substance. These marks are only visible with a specific type of light. They are usually hidden. A cheater may also use a special pair of glasses or contact lenses to see the marks. These lenses are usually fitted into sunglasses, unlike contact lenses that look just like regular lenses. This conceals them from the eyes of other players and doesn’t draw as much negative attention from fashion police.
A light-sensitive ink is another way to mark cards. This ink reacts to a specific wavelength of light and is often incorporated into a daub. Cheaters can bounce invisible lights off the surface and see the markings with a slightly colored lens or contact lenses.
Poker cheating glasses can be used to read invisible marks in marked cards. They are also used in magic shows and look like normal sunglasses, so other players don’t suspect that they are cheating devices. They are available in a variety of colors so that poker players can choose the one they prefer.