Infrared marked cards is one of the invisible marked poker cards and it can be used on some magic shows and entertainment TV shows!
You should use dedicated infrared ray camera to see the marks on the back of the poker cards or the side face.
However, if you use contact lenses or UV camera, the naked eyes can seen nothing. Even the infrared contact lenses cannot detect the infrared in k mark on the playing cards.
The marks on the back of the infrared marked cards are black which is clear for you to see. What's more, it can be used for a very long time.