A term used by sleight-of-hand performers to describe the phenomenon that something in black tends to disappear when placed against a black background and physical dimensionality tends to flatten out. For example, a conjuror can make himself seem to disappear by jumping behind a black panel in front of a black background, the action covered by a flash of light or smoke. This is now enhanced through the use of ultraviolet or black lights. Although rarely used as a full act, it is a popular technique in Prague. Fradulent mediums often used this technique to make things appear or disappear in dimly-lit séance rooms.