Luminous Invisible Ink Marking Decks
This very article is devoted to one of the most famous cheating methods applied mostly by poker cheaters or blackjack players called Card marking. The principle of this method is simple to understand: players use different liquids, devises or hooks to mark the cards that have the better value in order to recognize and get them during the game. Well, the understanding is simple but the performance is much harder. Actually nowadays it can be so difficult that the cheater who performs it may need the dealer as a partner. There are several methods to mark cards in a deck.
The juice marks method implies that a player marks cards in a deck by juice and those marks are invisible for average players who haven't been taught to read those before. The special glasses or filters are not necessary; all you need instead is a lot of practice to recognize such marking. The tint and shade are also used in card marking but efficiency of those depends on cards' back and the quality of cards.
The luminous ink is used in card marking for a long time. Those cards which were worked up with such ink cannot be recognized or read without special lenses or glasses. By the way, pit bosses and floor managers would be especially attentive to your 'glasses' in this case. Years ago luminous cards had a virescent hue but now the marking is absolutely invisible.