By Dyna Whiting
Updated Mar 24, 2022
Water vapor—the gaseous form of water—is normally invisible until it condenses into tiny liquid droplets. When these droplets coalesce in the air, they become visible as clouds or the familiar steam that appears when you exhale on a cold day. By using either low temperatures or increased mouth pressure, you can reliably produce a visible mist from your breath.
When you exhale in a cold environment, the warm, moist air from your lungs contacts the cooler outside air. The sudden drop in temperature causes the water vapor to condense into microscopic droplets that scatter light, creating a cloud.
Choose a location with a very low temperature—outside on a winter day or indoors near a freezer.
Take a deep breath and exhale slowly through your mouth. A visible cloud should form in front of you.
For a larger cloud, widen your mouth while exhaling slowly. A quick exhale will produce a lighter, shorter‑lasting cloud. Experiment to find the effect you prefer.
To prolong the cloud’s visibility, blow your breath onto a cold surface such as a glass pane. The droplets will condense on the glass and linger longer than in the air.
Gases are compressible, so the air in your mouth can be compressed to increase the likelihood of water vapor droplets colliding and coalescing. This method works regardless of ambient temperature.
Take a deep breath.
Fill your cheeks with air while breathing through the nose.
Apply gentle pressure to the air in your mouth without letting any escape, allowing moisture to evaporate into vapor under higher pressure.
After a few seconds, release the air quickly—say a short sound such as “pah” to aid the release.
You should now see a small cloud emerge from your mouth as the compressed vapor returns to normal pressure.
A cup of ice or a popsicle can also serve as the cold surface in Method 1—simply exhale slowly onto it to create a visible breath cloud.
When working with cold temperatures, dress warmly and be mindful of hypothermia or frostbite risks.
