X-Peri-Mas #14 – A Whoosh and A Cloud

There is a tradition of setting fire to alcohol as it soaks into a Christmas pudding. It always looks cool to have those blue flames licking up around the pud but there is a way to make it even cooler! We can vapourise the alcohol first and then set fire to it inside a bottle… The first bit makes a cloud, the second bit makes a whoosh!

You will need

  • A glass bottle
  • Isopropyl alcohol (also known as rubbing alcohol)
  • A cork that fits the bottle snugly
  • An air pump and a needle that fits that pump
  • A match
  • Two containers that you can put a lid on – one for any flammable waste (like the leftover alcohol and any tissues you use to wipe it up) and one for any hot waste like used matches.

Safety

It is really importance to do this right. You can end up in a fiery mess if you don’t take care around fire. Please do ask for some help here.

Any time you empty out the bottle after you’d added alcohol, pour it into a bottle of container that you can put a lid on. This stops any vapour building up when you light another match and it also stops you dropping anything hot into the flammable liquids.

Clean up any spills straight away. Flammable liquids and hot things don’t mix.

Be prepared to put the fire out. Have a wet tea-towel nearby and know exactly where it is. Don’t panic if a fire does start. Stay calm, put anything you’re holding down safely (you don’t want to drop anything that might make the fire worse! Especially if you’re holding something flammable…. put it down safely first). Gently place the wet tea-towel down over the flames. Don’t pick it up again until you’re sure it is extinguished.

Thank you for reading the safety bit – it’s boring but can make all the difference. Don’t use fire unless you’re confident. If something goes wrong, be calm and deal with it. Plan properly and you won’t have any problems!

What we’re going to do

Set up

Push the pump needle through the cork. It should just about poke out of one end. You can cut through the cork to make it shorter if you need to.

Attach your pump to the needle.

Pour a small amount of isopropyl alcohol into your glass bottle.

Push the cork into the bottle and hold it firmly in place. It will want to pop out as you pump the air into the bottle.

Pump the air into the bottle – you will feel the pump starting to get a bit harder to push soon but keep going. You’ll have to work out how much you need with some trial and error (some pumps are better than others and you might have some leaks in your set up).

A cloud in a bottle

Pull the cork out of the bottle and the cloud will form.

Even at 50 frames per second the cloud formed in between the frames. That means that is takes less than 0.02 seconds to form.. that is fast!

The frame before (left) while the cork is still in and the frame after (right) 0.02 seconds later.

In the frame before you can see the detail in the radiator cover behind (I know, flashy studio for me!) and in the frame after the bottle is filled with a cloud so you can’t see it any more.

A whoosh bottle

Turn the lights off.

Take a match and bring it close to the opening of the bottle. Since your cloud is made of flammable gas, it will catch fire. The flame will accelerate downwards into the bottle and make a fantastic noise! A roaring whoosh!

Turn the volume on – the sound is the best bit!

Both together

Here’s the video of the whole thing from one angle…

…and from another…

Try this out at home but please do be safe about it.

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