Defy gravity and make you egg fly upwards! This ‘Birthday in a Bottle’ demonstrations really tests your thinking on the old classic egg in a bottle experiment. Many people think gravity sucks the egg inside the bottle. Well, this experiment shows you that it is all to do with air pressure!


A large glass bottle with a wide mouth (we used a 500mL conical flask)

Several hard boiled eggs that have been peeled

Some cooking oil

Small birthday cake candles


Adult supervision



– Matches means you need an adult to help you

– Check the glass bottle that it has no cracks in it

– Careful not to drop glass bottle on the ground.


1. Push carefully 2-3 candles into the end of the boiled egg. Make sure the egg does NOT split and that the candles can fit into the mouth of the bottle.

2. Light the candles and place them inside the mouth of an upside down bottle. You may need two people for this section to hold the glass bottle safely.

3. Since this a ‘Birthday Egg Bottle’ singing ‘Happy Birthday’ may help the egg go into the bottle!

Did you like this? Would you like to take it further? Why not try our ‘Collective’ Bright Spark guides. These are packs contain multiple experiment guides on a ‘collective’ theme which include:

  • detailed explanation of the science,
  • suggestions for modifications on this experiment,
  • how to set it up more scientifically (variables etc),
  • mini-challenges
  • perfect for homeschooling or those wanting to ‘Go All the Way!’

Check out our product section.




Just like in our ‘Egg-Citing experiment’, as you heat the air with the candles it expands and exits the bottle. The candle flame goes out (due to using up the oxygen). The air inside the bottle now is under low pressure (as some expanded and exited the bottle and it cools down).



The air cools down (due to the candle going out and general heat loss to the surrounding air). As the air cools down it contracts. The outside air (which is higher in pressure compared to air inside the bottle) pushes against the egg and forces it into the bottle…. up against gravity pulling it downwards.

This shows that it is the air that pushes the egg inside the bottle and NOT gravity.

Some people think that the oxygen being used up causes a decrease in pressure and thus sucks the egg inside the bottle. Well, look at this chemical equation that shows you what happens when candle wax burns.

C25H52 +38 O2 —> 25 CO2 + 26 H2O

25 molecules of carbon dioxide (and water vapour) are produced which take up more space compared to the oxygen molecules.

Pressure in gases (Kinetic Particle Theory)

Heat, Temperature and Gases


Molecules: Two or more atoms joined together by a chemical bond. Oxygen and carbon dioxide are examples of molecules in this experiment.

Combustion: The burning of wax with oxygen is a chemical change called combustion.