This instructable will show you how to make a hot air balloon. This balloon will not use any sort of flame to make this, though. Instead, it uses the sun to heat the balloon. I saw this at American Science & Surplus, but it was $17.50 USD, so I wanted something cheaper; I went out and made my own!

Step 1: How It Works

The black color of the trash bags makes the air inside heat up. Everyone knows that hot air rises, thus making the balloon rise.

Step 2: Materials

These are the things you need:

30-Gallon Black Trash Bags
A large roll of duct tape (preferably black color), or a large roll of clear packaging tape
Scissors
A LARGE, dirt free environment without wind
Something to pump air with adequate volume (like the exhaust port of a shop vac)
Two or more hands
Free Time

Step 3: Prepare the Garbage Bags

First, take out about seven garbage bags. These will be the body of the balloon. After the bags are taken out, cut off the sealed ends of all but two of the bags. These are to extend the body of the tube, and also act as a coupler for each other garbage bag. Then, lay out four garbage bags, including one uncut garbage bag, on the large, clean surface. The surface needs to be clean, otherwise dust and dirt will prevent the tape from sticking to the bags. Finally, place the garbage bags inside one another, about 1 inch. Make sure that you place the bags inside one another so the air can travel though, without getting stuck in any crevices.

Step 4: Tape the Garbage Bags

When taping the garbage bags, make sure that the sealing edge of the bags is nearly dust and dirt free. This is because when you put the tape on, you need an air-tight seal. To start off, put tape on one side of the garbage bags, only going about 3"-4" underneath. After you do that to all the seams in the first section, flip the bags over and do it again. [See pictures 1-3]

Now onto the second section- Layout your final three garbage bags in the same fashion as the first, only take into consideration the overlapping of the seams, so the air will flow through properly when you inflate everything. Now, tape the three bags, flip them over, and repeat. Remember to go 3"-4" on the other side of the bags, otherwise they will fall apart when you try to flip them over.

Finally, it's time to tape all the bags together! Place the bag sections together, making sure they overlap. Next, tape everything together in the same fashion as the last sections.

Step 5: Inflate Everything

Now, it is time to inflate everything! First, take your handy scissors and cut a small slit into one end of the trash bags. Make this hole just big enough to blow air into using your pump (like the exhaust of a vacuum). Then, fill it up! This took me about two minutes with a shop vac. When your entire balloon becomes completely tight, seal the hole with a piece of duct tape. Also, you might want to attach a string so it won't float away!

Step 6: Have Fun!

Take the balloon out into the hot sun and try not to get this stuck 50' high in a tree! Also, try not to take this out on a windy day so it won't float away.