Why Glass Bottles Shatter at the Bottom When You Smack the Top with Your Bare Hands

By Casey Chan on at

There’s nothing quite like using the scientific method to figure out what’s happening in a silly party trick that we’ve seen way too many times (if you’ve been to bad parties, at least): the ol’ smack the top of a glass bottle and watch the bottom burst out in shards gag.

The always intrepid Mark Rober tested out multiple theories to find out what’s actually causing the bottom of the bottle to shatter, and used a super high speed camera to offer up convincing video evidence.

The theories he tests are all about pressure. One is that air pressure is what’s causing the bottom to give out. Another suggests that non-carbonated liquid works better in shattering glass than carbonated liquid and that the liquid getting smacked down to the bottom is breaking it. Finally, the air outside is the bottle causing it to break by pushing in on the bottom of the glass. It’s interesting to find out why, if only to see multiple glass bottles break.