ThermoHide
"Heat
Sensitive Camouflaged Message"
U.S.
Patent 5,873,604 - 6,396,927 - 5,636,874
5,695,220
G.B. Patent 2,276,588 B
Brisk
and rapid rubbing of the indicia areas reveals a hidden valid alert
message and verifies authenticity. Additionally, the heat from a color
copier will normally activate the hidden alert message causing the
accepting party to read the warning message. The activated message
reverts back to its camouflaged effect upon cooling.