Fun at Home - Hot Air Balloon

bin bag hot air balloon in flight

An investigation into expanding gas.

Use household items to build and launch an indoor hot air balloon.

Time to do and skill level

5 to 10 minutes, longer if you want to redesign your hot air balloon and flue.

Medium - Adult help is essential due to the use of plastic bags and hairdryer as a heat source. I strongly recommend this as an indoor activity so that your plastic bin bag does not get carried away by the wind away and pose a threat to wildlife

Equipment List

hairdryer scissors tape and cardboard

You will need:

  • An adult helper
  • Design Thinking Process PDF - download
  • Lightweight bin bag as your hot air balloon
  • Sticky tape
  • Scissors
  • Cardboard box
  • Hairdryer as your heat source


Step 1 – Don’t proceed without your adult. Check your equipment list and print off your Design Thinking Process or have it on screen.

Step 2 – Choose a suitable indoor space to test and launch your hot air balloon. Consider the following points.

  • If the balloon rises will it bump into anything on the way up like a ceiling fan or lighting
  • When the balloon falls will it land on any potential hazards like a cooker or open fire

Step 3 – Build a flue. A flue is the opening in a chimney that carries the gases from an open fire to the outdoors. The purpose of the flue in this challenge is to keep the bin bag away from the hairdryer while acting as a stabiliser to allow the bag to rise as successfully as possible. For the flue in this picture I chose a cardboard box and used scissors and sticky tape to change its shape.

alt text cardboard flue  cardboard flue and hairdryer

Step 4 – Your flue doesn’t have to be complicated, but it should have one hole at the base to allow the hot air from the hairdryer to enter and one hole on the top where the hot air exits and fills up the bin bag.

Safety note I have rested the hairdryer on the cardboard for the purpose of the photograph only, your adult should hold the hairdryer to make sure it doesn’t touch any surface that will melt or burn.

Step 5 – Inspect your bin bag for any holes. Patch them up with small pieces of tape if necessary.

Step 6 – Place your bin bag over the cardboard flue as shown in the image below

cardboard flue and bin bag

Step 7 – Ask your adult helper should switch the hairdryer on, choosing a gentle heat setting and direct the steady stream of warm air into the flue. It should only take a few seconds for your balloon to expand, if it doesn’t then you need to check for any holes where air might be escaping.

Step 8 – Watch as the bag begins to expand. You can slowly assist the bag to take shape by adjusting the corners as it fills out. I also tried testing different sized bags and increased the height of my flue by adding another cardboard box.

Step 9 – Let go of the bag and observe as it slowly rises into the air. Did your balloon launch successfully? Or did it flip over straight away and fall to the ground. Can you redesign your balloon to give it a more stable flight?

Step 10 – Ask your adult helper to switch the hairdryer off at the wall. Reuse or recycle your plastic bin bag appropriately.


What’s the science behind the bin bag balloon rising into the air? You’ve maybe heard that hot air is lighter than cold air when what we really mean is that hot air is less dense than cold air. The hairdryer heats or excites the molecules in the bag causing them to move apart from each other making the air in the bin bag less dense than the air outside it. You might have also heard that heat rises, but what would happen if you tried to launch your balloon in a room that was already full of warm air? For those of you with air conditioning units now is the time to vary the conditions. Select a cooler room temperature than you originally launched at and observe if your balloon rises more quickly or slowly.

Take a picture if it's safe to do so and share on Instagram hashtag #museumofthegreatsouthern or Facebook remembering to tag us.

This Fun at Home activity is presented by:

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