Applied Physics and the Concept of “Cavitation”

Blow the Bottom out of a Bottle
Whether you want to see applied physics and the concept of “cavitation” in action, or you just want to impress someone who’s never seen this trick before, blowing out the bottom of a full bottle is pretty darn easy. However, you need the right kind of bottle and the right kind of liquid in order to succeed. Also, you’re breaking a glass bottle here, so it’s best to take some precautions to avoid hurting yourself. After that, blowing the bottom out is simply a matter of giving the bottle’s mouth a good firm whack.

Part 1 of 3:Using the Right Materials

1. Use a glass bottle
Use a glass bottle. Expect plastic bottles to be much more durable than glass ones. So, in other words, don’t expect this trick to work on them. Stick to glass bottles, since these are much more likely to break (which, in this case, is what you want to happen).
The size of the bottle shouldn’t matter, as long as you can hold it up when it’s filled with water.

2. Empty the bottle of its original contents
Empty the bottle of its original contents. The one exception to this rule would be if it held flat, plain water. Otherwise, pour out or drink up the original liquid. Definitely do so if it’s carbonated (such as soda or beer). Expect the bubbles in carbonated beverages to prevent this trick from succeeding.

3. Refill it with flat water
Refill it with flat water. Once it’s empty, fill it up again with plain water. Remember, though: carbonation is the enemy, so don’t use seltzer or sparkling waters. Also, don’t fill it all the way up to the brim. Leave an inch or two (2.5 to 5 cm) of air on top.
You could possibly try using other flat, non-carbonated beverages, but water is a sure-fire bet.

Part 2 of 3:Acting Safely

1. Stay clear of electrical devices
Stay clear of electrical devices. Keep in mind that, if successful, you’re going to soak the immediate area with a bottle’s worth of water. Make sure there aren’t any wires or plugged-in devices nearby. Eliminate the risk of electrical shock.

2. Wear protective clothing
Wear protective clothing. Also keep in mind that glass is about to break and fall free from the rest of the bottle. Reduce the risk of getting cut by covering any exposed skin below your waist. Wear pants instead of shorts and shoes instead of sandals.

3. Hold the bottle over a bucket or other container
Hold the bottle over a bucket or other container. Remember: the glass that breaks free from the bottle may break again when it strikes the ground. Use a bucket to catch both the glass and the water. Make clean-up a cinch without the risk of cutting your bare feet later on if you step on a small piece of glass that you missed while sweeping up.

4. Aim the bottom of the bottle away from everyone
Aim the bottom of the bottle away from everyone. Keep other people’s safety in mind, too. Do not aim the bottle’s bottom at anyone. If you’re not using a bucket, clear the area and spread your feet wide apart.

Part 3 of 3:Pulling the Trick Off

1. Grip the bottleneck tightly
Grip the bottleneck tightly. Keep a firm grip on the bottle. At the same time, be sure to keep your hand close to the top. Expect each bottle to break differently when you do this trick, so keep your hand well away from the bottom to reduce the chance of cutting yourself.

2. Hold the bottle still
Hold the bottle still. Maximize all the force that you can muster when you strike the bottle’s top in just a moment. Do this by holding the bottle as still as you can. Expect to lose some force when you make contact if you’re moving the bottle this way and that.

3. Strike the bottle with your other hand
Strike the bottle with your other hand. Raise your free hand and then bring it down sharply. Strike the bottle’s mouth dead-center in your palm. Ideally, this will cause the bottom to burst. However, it may take a few tries, so just keep trying if at first you don’t succeed.
Alternatively, you can use a rubber mallet instead of your hand so it doesn’t become bruised or numb from too many tries.