Detecting marked cards
Some invisible ink marked cards can be identified by performing the gamblers' riffle test (also known as "going to the movies"). Looking at the back of the cards while they are being riffled, the marks will "dance" around the back of the playing cards like an old-fashioned cartoon, provided that the viewer knows what sort of marks to look for. The riffle test is less effective for detecting cards marked with luminous ink and juice ink methods.
Reflected light off the back of the card will reveal cut-out work (scratches or white ink), as well as many inks or solutions that tend to dull the finish on playing cards because they are alcohol-based. Only the highest quality solutions will not burn the finish of cards. Placing a drop of alcohol on a card and then looking at the finish by reflecting light off the back reveals the dulling effect that these cheap solutions can cause.