Marking cards with invisible ink
There are two ways to mark cards with invisible ink. One is marking cards by marked cards printer, and the other is marking cards by hand. Although these two ways are using with invisible ink, but the invisible marks made out are totally different.
The invisible ink marks made by hand are faint and weak, while the marks made by marked cards printer are clear and strong. Moreover, its marks will last a longer time, about 3 months from the time you using the marked playing cards.
If you want to read the cards marked with invisible ink, you need to wear luminous contact lenses or infrared sunglasses. Many clients prefer luminous contact lenses for they think marked cards contact lenses are more convenient than infrared glasses.