The Egg in the Bottle Trick

How to get the hard-boiled egg into the milk bottle.

The Egg in the Bottle Trick
Here's a classic science experiment that is more than a hundred years old and is guaranteed to fool your friends. The original demonstration used a hard-boiled egg and a glass milk bottle. Since old milk bottles are hard to come by, here's a modern day version of the same experiment, only this time we're using a juice bottle and a water balloon. For even more fun, try our "eggsclusive" upside-down version of the trick!


  • A wide mouth juice bottle
  • Hardboiled eggs
  • Several strips of paper (2 x 6 inches)
  • Matches
  • A few balloons
  • Water

Warning: This experiment requires the help of an adult partner. Don't just pick any adult... try to find a smart one!
  1. Carefully fill the balloon with water so the balloon is about the size of a tennis ball. Tie it off. Make several balloons just in case the first one breaks!
  2. Rinse out the bottle to remove any leftover, sticky, slimy stuff that might be in the bottom. Before going any further, make sure that the water balloon is slightly larger than the mouth of the bottle.
  3. Here’s the challenge... Your job is to find a way to get the balloon into the bottle without breaking it. How are you going to do it? It’s important that you take a minute to test out some of your ideas before jumping ahead to read our solution. Keep trying! Once you've come up with your hypothesis, read on to find out our answer!
  4. Start by smearing some water around the mouth of the bottle.
  5. Have the adult light a match and set the strip of paper on fire. Quickly put the burning strip into the bottle. Be careful you don't accidentally burn your fingers.
  6. Immediately cover the mouth of the bottle with the balloon. In just seconds, the balloon will start to wiggle around on the top of the bottle, the fire will go out, and some invisible force will literally “push” the balloon into the bottle. That’s amazing!
Now that you've mastered the trick, it's on to the next challenge. Can you get the balloon back out of the bottle? Use what you learned about air and air pressure to come up with a way to get the balloon back out. Here's a hint... Try sneaking a straw alongside the balloon when you pull it out. If the outside air can get inside the bottle, the water balloon will come out!
Try it with an egg!
Now that you've mastered the technique, repeat the steps above substituting a hardboiled egg for the water balloon. The trick here is to find an egg that is just a little bigger than the mouth of the bottle - medium size eggs work the best. The other little secret is to grease the mouth of the bottle with vegetable oil so the egg slides right in!
The Upside-Down Twist
All you need for this "eggciting" variation is a hardboiled egg, a bottle, several birthday candles, and a match.
  1. Carefully hold the wider end of the egg in one hand and slowly push two birthday candles into the narrow end of the egg.
  2. Light the candles (with the help of an adult) and sing happy birthday to the egg.
  3. Turn the bottle upside-down and slowly move it into position above the flaming candles.
  4. Allow the flames to heat up the air inside the bottle for just a few seconds and then place the bottle down over the candles. The candles will go out and with a "Pop!" the egg will squeeze up into the bottle.
Want to get the egg back out so you can do it again? Try this, if you dare... put your mouth over the mouth of the bottle and forcefully blow air into the bottle. The egg should pop back out of the bottle right into your mouth! Can it get any cooler than that? (Check out the video called Egg in the Bottle - Upside Down Twist.)

How does it work?

In the traditional version of the Egg in the Bottle Experiment, the burning piece of paper heats the molecules of air in the bottle and causes the molecules to move far away from each other. Some of the heated molecules actually escape out past the egg that is resting on the mouth of the bottle (that’s why the egg wiggles on top of the bottle). When the flame goes out, the molecules of air in the bottle cool down and move closer together. This is what scientists refer to as a partial vacuum. Normally the air outside the bottle would come rushing in to fill the bottle. However, that darn egg is in the way! The “push” or pressure of the air molecules outside the bottle is so great that it literally pushes the egg into the bottle.
In the Upside-Down Twist, the science is the same as the traditional Egg in the Bottle trick, but the whole thing is just inverted. It's a nice twist on a classic science demonstration.


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