Here's a forceful demonstration-over 1,800 lb of force! This demonstration will convince students that air exerts significant pressure. Simply place about a centimeter of water in the bottom of the can and heat it until it boils and steam comes out of the uncapped top. Remove the can from the heat, cap tightly, and watch and listen to the drama. As the can cools, a vacuum forms inside and the can dramatically collapses. A real attention-getter. Includes one can and detailed instructions.