Part I: Card Game Cheating · CARD MARKING METHODS
Luminous Marking (Invisible Ink)
How it works
Luminous marking uses special inks that are invisible to the naked eye under normal lighting but become visible when viewed through filtered lenses or special lighting conditions. Original systems used red-tinted lenses with greenish ink on red-backed cards. Modern systems use chemicals that respond to specific wavelengths of light, including UV and IR. The marks are applied to card backs before play, typically in patterns that indicate rank and suit. The cheater wears special contact lenses or glasses with the appropriate filter to read the marks.
Where it appears
Poker, Blackjack, Baccarat, virtually all card games
On the record
Luminous marking systems have been used since the early 20th century. The technology has evolved significantly - modern systems use chemicals that only respond to very specific, narrow light wavelengths, making detection increasingly difficult without specialized equipment.
Detection & prevention
The paid halfHow a monitoring room catches luminous marking (invisible ink), and what stops it recurring — written for the desk, not the reader.
Detection · 66 words
Prevention · 55 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.