Make a Hot Air Balloon from a Plastic Bag and Some Birthday Candles

For years I'd heard that you could make a hot air balloon from a garbage bag. When I finally tried it, I found that--as with so much of life--the "devil's in the details." Here's what I learned, in the form of the embedded instructional videos below, with the help of some of my students.

REALLY USEFUL UPDATES: By far the biggest problem with this project is finding bags that are thin enough. Most garbage bags sold through retail are much too thick and heavy. However, some people have sent in some solutions. Steve Mazzanti, a Technology Instructor in Athens, Texas has used bags from the dry cleaners, which I mentioned in the videos. But the bags have a pesky hole at the top where the hanger goes through. I've been taping the the top, but Steve welds the plastic together with a clothes iron, first putting paper under and over so it doesn't stick. That sounds like an easier and better way. He even welds bags together end to end!

Richard Brown, a math/science teacher at Watertown High School in Connecticut, informed me of a widely distributed bag that worked for him. Look for Ruffies 8 gallon Color Scents (they smell like vanilla) at department stores (at least in North America--people from other continents please let us know where you've found thin bags). If you Google it you can see what retail outlets sell them near you. At 8.9 microns the bags are half again as thick as the thin bags I use, but Rich got them to fly (you might have to use a fifth candle).

Finally, I knew there must be a better way to attach the candles than the way described in the video. Somebody (I can't find the e-mail) suggested hot glue, which works well for me. And when I put them all together, in a line, it's much easier to light the candles.

Part 1, Introduction, covers history of hot air balloons in Asia and France, modern day ballooning, and some basic terms. If YouTube is blocked at your school, try this SchoolTube link Part 1

Part 2, How it Flies, presents some amazing facts that allow hot air balloons to fly, woven into cool videos of people-carrying balloons preparing for take off. SchoolTube Part 2

Part 3, Fuel and Safety, shows why we think volitile fuels are a bad idea (we use candles) and I make the case that hot air balloons, education and kids (with adult supervision) all go together.SchoolTube Part 3

Part 4, What You Need to build a hot air balloon: aluminum foil, plastic drinking straws, birthday candles. And the only tricky part is finding a trash can liner that's thin enough, but we'll show you where to look and how very thin plastic is measured SchoolTube Part 4

Part 5, Build and Fly gives the construction details for keeping the botom of the balloon open and holding the candles and we make the case for flying indoors. You do not have to weigh anything, but we do on the video just to stay conscious of keeping it light. SchoolTube Part 5

Part 6, Using Smaller Bags bags is more of a challenge than using larger ones. We'll show you why and present some tips for making them work. Plus a (green screen) ride in a hot air balloon for the student volunteer presenters. SchoolTube Part 6

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I put a lot of work into making these instructional videos. It's encouraging to me to know that people are putting the information to work and I improve the instructions when people point out when something is not clear ( I answer specific technical questions as best I can, too). Furthermore, hundreds of people have sent me innovations that have made all the projects on http://www.sciencetoymaker.org/ better. So, consider sending me feedback about how the hot air balloon project went for you. Contact

********************************************************** SOME COOL FEEDBACK***************************************:

I am homeschooling my 6 and 8 year old boys this year and since we're reading The Twenty One Balloons, I got the idea to see if it would be possible to make a real, flyable hot air balloon.  I was SO happy to find your site and your excellent step-by-step videos.  The following are the pictures we took of our process (our son made the balloon with an older friend).  They were very able to do most of the steps fairly independently, which was fun to see.  We were able to get the right kind of custodial grade bag from our church, where they had rolls of them.  GREAT PROJECT!
Jessica Smith

A video of us flying it:http://youtu.be/SLMaHkUUfco Measuring the diameter of the bag

Cutting the foil square

Making the straw frame

hot gluing on the candles (we started with 4 and I did cut them down out of weight consideration)

Straw frame done!

Taping it all together

4 candles gave inflation, but no lift.

The boys suggested more fire power! so we added 2 more candles and got lift off!

They wanted to try it outside and it didn't last long in the breeze.

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And here is a video from two young scientists, Caroline and Natalie from Iowa City

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Professor Adolfo Bastida of the University of Murcia in Spain and who also runs a science program for young people sent these pictures. The project was complicated by trying to find the right kind of plastic bag. "You cannot imagine how many different bags we tested. Finally we found it: that right plastic is used by some hair dressers to cover the shoulders of their clients! Last friday we did our ballons following your directions and it was amaizing."

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This external link is to an artist named Joshua Allen Harris who makes surreal inflated creatures from thin plastic bags. I doubt it could be applied to a small hot air balloon (surface area, see Part 6), but the shear brillaince of the art is worth a look http://www.youtube.com/watch?v=PH6xCT2aTSo&feature=channel_page

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