How to Make a Hot Air Balloon – Goes for miles, often reported as a UFO :)


The hot air balloon is the oldest successful device capable of carrying humans in flight–the first successful manned flight was on November 21, 1783, in Paris by Jean-François Pilatre de Rozier and François Laurent d’Arlandes.

A hot air balloon is constructed out of an envelope (the bag that holds the hot air) that is capable of withstanding the heat from the air, beneath the envelope is a container of some type (called a gondola when it carries people in it) which contains the payload along with a source of heat that’s typically an open flame. The heated air that’s contained in the envelope makes it buoyant because it has a lower density than the air outside, which is much colder relative to the air inside. Now

what we’ve got here is a very simple and easy to make hot air balloon that consists solely of some birthday candles, a bit of balsa wood, and a vegetable bag from the grocery store–I love that he says these things have been mistaken for and reported as UFO’s, that just makes me want to do

it so much more 😀 , have a look and stay tuned afterward for some science:

The envelope doesn’t need to be sealed at the bottom like with gas (helium) balloons because the gas (in this case air) at the bottom of the envelope is at the same pressure as the surrounding atmosphere. When you

raise the temperature of the air contained in the envelope, this makes it lighter than the surrounding atmosphere of air, thereby causing it to literally float, just like a boat in water: the balloon floats in the earth’s atmosphere near the ground because of the buoyant force exerted on it, which is the same force that

causes buoyant objects, such as boats, to float in water and is described by Archimedes’ principle: “Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.” So therefore the amount of lift (which you could also call buoyancy, technically) produced by a hot air balloon is dependent mostly on the temperature difference between the air inside the envelope and the air (atmosphere) outside the envelope.

Additional Resources

Here’s a really cool set of instructions on how to make a hot air balloon with some tissue paper, it’s aimed at 6th graders and the balloons certainly end up a lot prettier than one made from a plastic bag 🙂


  1. Very cool…. but……

    Doesn’t this seem like a ridiculously unsafe thing to do? Once you let that puppy loose, you have no control over where it will go/land… and let’s face it… it IS transporting fire in a bag that is, itself, flammable.

    When I first looked at this I thought it might be a fun little experiment, but when I could not think of a place or situation in which I’d feel comfortable letting this thing go… I sorta changed my mind. *Maybe* if I had it on a kite string and didn’t let it get too far. Not sure if it would have enough lift, though, to support the weight of the string.

    Looks neat, but seems like all kinds of bad in the making to me.


  2. Oh you’re absolutely right, I seem to recall there was a big fire started in london because this particular device used to be a really popular toy with kids back in the 19th century and one of them landed on someone’s roof and ended up burning down half a city block or some such thing.

    Yes, do be careful with these, having them on a string or something might not be a bad idea unless you’re in a VERY rural area…