To demonstrate the force created by freezing water.
Ice bomb nipple with two end caps, liquid nitrogen in styrofoam bucket, gloves, and steel outer bucket with weighted cover.
We use short pipe nipples because they are much cheaper than the traditional cast iron spheres and they seem to work better. The end caps can be re-used.
A short cast iron nipple with caps on each end is filled with water and dropped into a container of liquid nitrogen. Within about one minute the water freezes, expanding sufficiently to break the cast iron pipe with a loud crack and a big cloud of vapor. Be careful to fill the pipe completely with water before immersing it in liquid nitrogen. If it does not explode, leave it alone; it may still be dangerous.
Sargent-Welch Scientific Company, Instructions for use of No. 1670 Ice Bomb. Lecture-Demonstration data on galvanized steel fittings for UM ice bomb. Herbert M. Reese, Freezing in Water Pipes, AJP 19, 425-426 (1951). David Miller Raybin, The Stones of Spring and Summer, TPT 27, 500-502 (1989).