How to Make a Cloud in a Jar

Create an amazing cloud formation inside a jar with this simple science experiment that teaches kids about weather and water cycles.

1. What You'll Need. Gather these simple household items: a clear glass jar with a lid (mason jars work perfectly), very hot water from the tap, ice cubes, hairspray or matches (adult use only), and a dark piece of paper or cloth to place behind the jar for better visibility. Make sure the jar is clean and completely dry before starting.
2. Creating Your Cloud. Fill the jar about one-third full with very hot water from the tap. Swirl the water around to warm the glass, then pour out all but about an inch of water. Quickly spray a small amount of hairspray into the jar (adults should handle this step) or drop in a just-extinguished match for smoke particles. Immediately flip the lid upside down and place it on the jar, then put 3-4 ice cubes on top of the inverted lid. Watch as your cloud begins to form within 10-30 seconds.
3. Observing and Understanding. Place the dark paper behind your jar to make the cloud more visible. You should see wispy, white formations swirling inside the jar, just like a real cloud. The cloud forms because the hot water creates water vapor, the ice provides a cold surface for condensation, and the hairspray or smoke gives tiny particles for water droplets to attach to. Remove the lid quickly to see your cloud escape, just like fog rolling out.
4. Making It Educational. Explain to your children that real clouds form the same way in the sky. Warm air rises and cools when it meets cold air high up in the atmosphere. Tiny particles of dust or pollen in the air help water droplets form, creating the clouds we see. Try the experiment multiple times, changing one element each time - use cooler water, less ice, or skip the hairspray to see how each part contributes to cloud formation.