How do you make a cloud? On her show, Head Rush, Mythbuster’s Kari Byron demonstrates how clouds are formed by making one in a bottle.

For this experiment, you can use a bicycle pump with a rubber stopper attachment, rubbing alcohol and a clear 1 liter bottle. Don’t forget goggles and some adult supervision! Steve Spangler’s Science has more:

The reason the rubbing alcohol forms a more visible cloud is because alcohol evaporates more quickly than water. Alcohol molecules have weaker bonds than water molecules, so they let go of each other more easily. Since there are more evaporated alcohol molecules in the bottle, there are also more molecules able to condense. This is why you can see the alcohol cloud more clearly than the water cloud.

Clouds on Earth form when warm air rises and its pressure is reduced. The air expands and cools, and clouds form as the temperature drops below the dew point. Invisible particles in the air in the form of pollution, smoke, dust or even tiny particles of dirt help form a nucleus on which the water molecules can attach.

From the archives: clouds and experiments.

Update: Via @nicolasdickner, here’s an easier version of the experiment:

All you need is an empty water bottle, cap, and rubbing alcohol. Pour in some rubbing alcohol. Swish it around. Cap it. Grab the bottom half of the bottle. Start twising it to create pressure. Keep twisting until you cant twist anymore. Uncap it quickly.. Let it pop!