WATER & GLASS EXPERIMENT

[SCOOTERACQ]

DOES ANYONE KNOW ABOUT AN EXPERIMENT USING A FULL GLASS OF WATER AND A FLAT PIECE OF GLASS WHEN YOU REMOVE THE PIECE OF GLASS FROM UNDER THE FULL GLASS OF WATER THE GLASS STAYS FULL WHILE UPSIDE DOWN?

[jenstar]

Ah yes, a popular party trick, that one. You fill a glass to the top with water and stick a beermat or postcard on top, then you turn it over and quickly whip the postcard away, and if you hold the glass steady enough, the water doesn't pour out (at least, not straight away) because the air pressure beneath is strong enough to hold the water in.

[Mortartube]

Rather than just place a beermat etc on top of the glass, slowly slide it across the mouth of the glass. Keep the beermat level. The glass should be so full that it is about to overflow, so no air gets trapped beneath it.

[Bert]

You can try it till you run out of water and it won't work because the mouth of the glass is too wide. It only needs the surface to have the slightest imperfection and an air bubble will go to the top (or bottom) of the glass and the water will fall out. You stand a bit of a chance with something like a champagne flute, which has a relatively narrow mouth. Anything else is a "magic" trick, which I guess is done with clingfilm.