How to make a Cloud in a Bottle

What you will need:

  • 2-liter clear plastic bottle with cap, a quarter filled with warmish water
  • Smoky splint
  • Safety glasses


  • Wear safety glasses!
  • Light a splint and then blow it out so that it is smoky.
  • Put the splint just inside the bottle.
  • Squeeze the bottle as you do this.
  • When the smoke is in the bottle release the pressure on the bottle and put a cap on it quickly.
  • To make the cloud, squeeze the bottle and release it. Is there a thick cloud each time you release the bottle?

Why this happens:

Even though we don’t always see it, water is all around us. These particles are called water vapour. When the particles are bouncing around in air, they don’t normally stick together. Squeezing the bottle forces the particles in the bottle together. The pressure in the bottle goes up and it heats up a little bit. Releasing the bottle lets the pressure drop and it cools down. As they cool the water and smoke molecules start to stick together, forming tiny droplets.

Clouds are nothing more than big balls of tiny water droplets! Real clouds form as warm air rises. As air gets higher, the pressure is less. The air expands, which causes it to cool. As it cools below the dew point, water vapor forms the droplets we see as clouds. Clouds can form around tiny particles of pollution, salt water, smoke or dust.