Water Stands like magic on a perforated screen. Try to suspend as much water as you can on the metal screen. By turning the tube quickly and smoothly to an exact vertical position, two forces conspire to suspend water above a metal screen. Attraction between water molecules (surface tension) in the upper chamber, and a higher air pressure in the lower chamber help achieve this effect. Attraction between water molecules (called surface tension) holds the water together so it doesn't drip through the holes in the metal screen.