Instant Clouds: Just Add Pressure!





Introduction: Instant Clouds: Just Add Pressure!

About: The Oakland Toy Lab is a community-based wonder lab for students to build, tinker, explore, make, break, and learn! We are writing up engaging science experiences so that educators, parents, youth, and famil...

Time to make Zeus jealous. Mama always told you that you can plan a pretty picnic, but you can't control the weather. Well the forecast today is that your mama is, sadly, 100% wrong. With a little bit of pressure applied, a front of cloudy weather will be moving in to your bottle in less than a microsecond. You can re-create the same process that clouds go through when forming to make your very own pet cloud. There are other methods out there, but I truly prefer this one, and wanted to share it because it's so easy and stunning!

  • What: Instant Cloud!
  • Concepts: pressure, meteorology, physics, adiabatic process, water cycle
  • Materials:
    • Rubber Stopper with no hole (can get at hardware store)
    • Water Bottle (bigger is more fun)
    • Isopropyl Alcohol (99%)
  • Tools:
    • Bike pump with sports needle
    • Drill

All right! Let's start clouding around!

Step 1: The Fine Print: Materials, Science, and Caution

You are about to be the master of weather, and with that comes great responsibility. First, gather up the 99% isopropyl alcohol from a pharmacy, your stopper with no hole, and a bike pump.

The reason I use alcohol for this instead of water as some others do is because of the specific scientific process our cloud is about to go through. One of the processes by which clouds are formed is referred to as a adiabatic process, which air goes through as it rises in the atmosphere. As hot air rises and cools, that body of air expands as there is less pressure on it at high altitudes. That is why balloons expand and eventually pop up high.

The large expanding bit of air means that the individual molecules don't bump into each other as much, and that means a drop in overall temperature. This makes the air cool, and as it does so, it eventually falls below the dew point, which is when water vapors start to collect in droves. They often nucleate around particles in the atmosphere, but are basically getting released from high pressure to low pressure and are thus forming! A great write-up can be found here.

We are basically going to put the liquid alcohol under a lot of pressure, and then when the pressure drops the molecules act like springs that have been squished too tight, and they release into the air in vapor form. This works so much better with alcohol because the hydrogen bonding (cohesive force) isn't as tight as with water, so they spring up easier.

KIND CAUTION: Because we are using alcohol, please be careful with flames near the bottle especially as it volatizes. It can turn the whole system into a fiery rocket, which some people intentionally do (and is amazing), but that's a separate experiment to be prepped for. As always, too, be careful when pumping up and releasing big amounts of pressure, especially with students. They can cover their eyes, and most importantly keep a hand on the pump parts so they don't fly up mid-experiment.

Step 2: The Cloud Plug

Take your rubber stopper and the smallest drill bit you have (we used 1/16"). Make a hole through the middle of your rubber cork, which will serve as a pilot. With a little squeezing and rotating, push the sports needle through. Then attach it to your bike pump, and your cloud plug is all set. You're ready to take on some serious pressure!

Step 3: The Cloud Bottle

Take any labels off your cloud bottle so you can see it clearly. Bottles with sturdy thicker plastic work best for this experiment (often seen in 2 liter bottles). Carefully pour a small amount of isopropyl alcohol into your container (about 1/3 cup should do). Then you're ready to go!

Step 4: Pump It Up and Release!

Place your cloud plug into the bottle, and hold it there firmly. If you have a class for a 1.5L bottle, have them count 10 pumps out loud to increase the pressure in the bottle. When you release the plug, a cloud will instantly be formed with a dramatic sound and puff. YAY! A CLOUD!

From there, squeezing the bottle, you can make little cloud rings, or you can place the plug in to fascinatingly see the cloud disappear with the next press of the bike pump. With the same small amount of alcohol, you can repeat this process many, many times, and try out variations. What happens when you pump it less, more, when you try it with water, oil, milk?

Hope you enjoy turning cloudy weather into a good thing. As always, keep exploring and reach out with what you think below!



    • Oil Contest

      Oil Contest
    • Creative Misuse Contest

      Creative Misuse Contest
    • Water Contest

      Water Contest

    27 Discussions

    Very cool! So.... Could this process be used to make vapor shots?

    4 replies

    Bad Idea !

    In the rural areas people used to die from "stomping the silo" which is the same principal. BTW: They die of alcohol poisoning !

    they now make machines designed to vaporize alcohol but they are illegal in some (if not all) parts of the U.S.

    My friend did that once and landed himself in the hospital. Your lungs are very sensitive and are used for exchanging oxygen and carbon dioxide. Don't risk permanent lung damage. Trust me, it's not worth it.

    Alright, so people don't recommend doing this with ethanol...

    Now to the propellant part. Could I theoretically use the technique for a spud gun? :D

    1 reply

    you can light the alcohol and the effect is very similar to a whoosh bottle. look them up.


    As a professional chemist. I would suggest sticking to water - the thought of vapourising IPA or much worse, acetone is something I wouldn't go near. You might remain lucky, but an acetone fire is a proper fireball.

    No chance of getting the ingredients in the high sreet in the UK, the homemade bomb-makers have put paid to that.

    1 reply

    I appreciate the caution and it is well deserved. Vaporizing volatile liquids is dangerous to an extreme, no doubt.

    That's really cool. I wonder if you could use this technique to make an acetone vapor for smoothing ABS 3D prints?

    3 replies

    No need to do that. Just put your piece in a big stainless or glass container (I use an empty paint gallon with the lid) on a small pedestal and put just a little acetone in the bottom. Make sure the acetone doesn't touch your art directly. The acetone will vaporize at room temperature. I do it outside to reduce all the risk of inhalation, explosions, etc

    I think one concern is the vapor gradient isn't very even if your part is near the acetone, so you end up needing a bigger container. I think the interest is in condensing a big uniform cloud around your part, but I don't think this would be helpful much over the process you described [just regular acetone vapor smoothing].

    Could you do this with liquor?

    I first learned how to do this from some science show. The 'wizard' said you could use after shave lotion and it worked just fine. You don't need anywhere near 99% isopropyl. That's expensive and unnecessary. BTW

    Iso-HEET in the red bottle is 99% IPA. $3.99 retail for a tiny bottle but cheaper at Walmart. You can use 91% or 70% medical grade alcohol.

    I used to use a glass 1 gallon jug. I've seen online people using a 5 gallon water jug. That would be way cool.

    Did it today with the kids. A complete success, with a couple of variations:

    1. Used a foot pump, not the a floor pump.
    2. The supermarket only had 91% isopropyl, not 99%.

    Probably because of that, it took 20 pumps to vaporize the spirit, not 10.

    Thank you for sharing a groovy instructable!