So they designed a better mechanism. The Mentos stay stacked in a PVC pipe, held up by a removable pin. The pipe is cemented onto a hollowed soda bottle cap underneath, and on top is a PVC cap drilled or cut with one or more holes that act as different types of nozzles – the keys to Eepybird’s dramatic fountain effects. The biggest challenge was finding a cement that worked well on both PVC and bottle cap plastic.

You can Try This at Home using Eepybird’s kits, which Fritz and Stephen produce themselves at “Eepybird Labs” in Buckland, Maine. Just make sure to use warm diet soda—warm soda shoots much higher than refrigerator-temperature, and sugar-free sodas have slightly more carbonation, don’t get sticky, and don’t attract bugs.

–Paul Spinrad