Hydrostatic glass

A transparent plastic glass is filled with water. Immediately, the rim of the glass is covered with a piece of paper and the glass is turned upside down. The liquid stays in the glass! Then the magician removes the paper... and the liquid still remains in the glass! Afterward, the magician announces that the liquid will fall... and after the magician's words, the liquid falls!

The glass is made of high-quality plastic, is 11.1 cm high and has an opening diameter of 7 cm (2.76 inches).