Part I: Card Game Cheating · CARD MARKING METHODS

Light-Reflective Chemical Daubs

How it works

This advanced marking technique uses chemicals that are only visible when exposed to a specific wavelength of invisible light. The cheater applies a light-reflective chemical daub to card backs during play, then uses contact lenses with a special light filter to view the markings. The contact lenses appear as normal reading glasses with clear lenses. The invisible light source bounces off the marked card back and is filtered by the lenses, making the mark visible to the cheater. This system is extremely difficult to detect because the marking chemical is invisible under normal and UV light.

Where it appears

All card games

On the record

This technology was highlighted at the World Game Protection Conference by researcher Terry Roses, who demonstrated that modern marking chemicals have improved dramatically and can be formulated to react only to very narrow, specific light wavelengths.

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.