Cloud in a Bottle | Cloud in a Jar Science Experiment

Cloud in a Bottle (Cloud in a Jar Experiment)
Conjuring a cloud inside a bottle may help you figure out how they form outside in the sky.
Warm, moist air rises — and then cools — in the atmosphere. The result? Beautiful, puffy clouds. Tiny water droplets become many different kinds of clouds at many different altitudes, depending on the conditions. Making your own cloud in a bottle is a popular activity in many science books; however, it can be a little tricky to pull off in real life. Sometimes, the results can be hard to see — but as they say, practice makes perfect! (It also helps to use some ingredients other than water, too.) In this fascinating cloud experiment, you’ll learn how to make a cloud in a jar. In turn, this will help provide an educational visual about weather, cloud formation and water vapor.
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Experiment Materials

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Let’s start with making the easy cloud first and then you’ll know what to do for the tougher version. Wear safety glasses and pour a little alcohol into the bottle so it puddles in the bottom.


Swirl the alcohol around inside the bottle. Make sure it coats the lower sides of the bottle.


NOTE: The metal inflation tube needs to go through the stopper. From the bottom of the stopper, drill a hole through the center of the stopper that’s a little smaller than the inflation tube. The tube should slide easily through the stopper from the top to the bottom but still be tight enough to seal the air inside the bottle. The tip of the tube goes inside the bottle and the pump connection goes outside. Attach the pump to the inflation tube.


Insert the stopper into the bottle and pump eight to ten times. As you start to pump, you’ll notice that the stopper wants to pop out. Hold it tightly in the bottle opening so it doesn’t. It may be stronger than you think!


When you’re ready, quickly remove the stopper and watch the cloud form almost instantly in the bottle. If the cloud is faint or just a small puff of one, you’ll need to add more pressure in the bottle before you pop the stopper.

How Does It Work

Although you cannot see them, water molecules are in the air all around you — even when it is raining! These invisible, airborne water molecules are also called “water vapor.” When water vapor bounces around within the atmosphere, it has a lot of motion energy. For this reason, it doesn’t normally stick together.
When you pumped air into the bottle’s enclosed space in this cloud in a bottle experiment, it forced the water vapor to squeeze together (or to compress). Releasing the pressure quickly allowed the air in the bottle to expand quickly. As a result, the temperature of the air in the bottle became slightly cooler. This cooling allowed the water vapor to stick together, or to condense, more easily. Tiny water droplets then formed. Clouds are nothing more than gazillions of groups of tiny water droplets!
What’s so important about rubbing alcohol in this experiment? Well, rubbing alcohol evaporates faster than water, which causes a more visible cloud to form — right before your eyes! Alcohol molecules have weaker bonds between them than water molecules do. (That means that they will let go of each other easily.) The result is that there are more evaporated alcohol molecules in the bottle that are able to condense at the lower pressure. That’s why you see the alcohol cloud more clearly than the water vapor cloud earlier on in the pumping process.
Those white, fluffy cotton candy-like clouds on Earth form when warm air rises and its pressure is reduced. The air expands and cools; clouds then form as the temperature drops below the dew point. Invisible particles in the air — think pollution, smoke, dust or even tiny particles of dirt — become a nucleus on which the water molecules can attach themselves. Voila! These particles go from invisible to visible. A cloud then forms and can take a shape that’s only limited by your imagination: could it be an elephant, a shark, a bear? Perhaps you see a continent or a country — or an alien?

Take It Further

You now have a pretty good idea about what to expect in this cloud in a jar experiment. This time, it’s time to be more realistic.

• Put on your safety glasses.

• Pour enough warm water into the bottle to cover the bottom. (You want more water than you had alcohol.)

• As before, swirl the water around to coat the sides and put the rubber stopper into the opening.

• Pump about five times. (Hang on to that stopper!)

• After five pumps, pull the stopper out of the bottle. You may see a very faint “poof” of a cloud. There probably wasn’t enough pressure in the bottle to make a really good cloud — yet!

• Repeat the pumping action, but instead of five pumps this time, go for ten. You’ll notice that the more you pump, the harder it will be to keep the stopper in the bottle. (OK, let’s all say it together: Duh!) Pull out the stopper and you may see a slightly more visible cloud this time.

• See where this is going? Fill the bottom of the bottle with warm water again and pump about 15 to 20 times. You want to put about 20 psi (103 cmHg) of pressure into the bottle.

• When you remove the rubber stopper, you should see a pretty good cloud this time. Yes, it’s more difficult to make a cloud using water than alcohol. Give some thought as to why that’s true.

The Clouds in a Bottle: A Lesson on Weather and Water Vapor

This cloud in a jar experiment provided you with a unique visual on how water vapor in our atmosphere is formed. Because clouds seem like they are always there, it’s easy to take them for granted; however, they’re a great lesson on wind, air, weather and Earth science.
In this cloud experiment, you bring the amazing process of cloud formation and the principles of water vapor to eye level. Then, you’re able to get hands-on with this cloud in a jar experiment: it’s easy to see just how cool these fluffy puffs of water vapor actually are! This cloud experiment is a great addition to a weather unit. Discuss the different types of clouds, like cumulus clouds, cirrus clouds and stratus clouds. Talk about the weather conditions that go along with each of these cloud types.
Learning how to make a cloud in a bottle is fun and informative. Incorporate this cloud experiment with some other of our weather experiments that are easy and fun to perform at home or at school. Learn about solar phenomena like UV rays and solar eclipses. See convection currents, create a tornado in a bottle or have a blast with instant snow. There’s just so much science to be explored and discovered at Steve Spangler Science! Check out our online experiment library for other science experiments for kids.

Special Thanks

Sources for this information included the Exploratorium website and the National Hands-on Science Institute.

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Cloud in a Bottle Kit

Our Cloud in a Bottle Kit comes with everything you'll need to do this experiment!

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