Part I: Card Game Cheating · CARD MARKING METHODS
Juice Marking
How it works
Juice marking uses a specially formulated chemical solution that subtly alters the pigmentation on the back of playing cards. The marks are invisible to untrained eyes but readable by those who know what to look for. The “juice” is typically applied in small patterns or dots on the card back design. Different recipes exist for different card back colors (red vs. blue). Professional juice is extremely subtle and can be read from across a crowded room by a well-trained eye. The marks may correspond to card rank, suit, or both.
Where it appears
Blackjack, Poker, Baccarat, Three Card Poker, any card game
On the record
Juice marking has been used by professional card mechanics for over a century. Bill Zender, a noted gaming consultant, has extensively documented modern juice marking techniques and the development of detection technology to combat them.
Detection & prevention
The paid halfHow a monitoring room catches juice marking, and what stops it recurring — written for the desk, not the reader.
Detection · 60 words
Prevention · 48 words
Published as a detection reference for surveillance, compliance and gaming-operations professionals. Thresholds and tuning are set by the property. Nothing here is instruction — the method is described so it can be recognised.