This hot air balloon was hot-iron seamed and made with 0.31 mil polyethylene. I have always wanted a hot air balloon, but this one will do for now. It was put together in one day. You preheat it with a torch and you can tether it like a kite. One preheat lasts a few hours. I have a second hot air balloon in progress – double the size, this time in black polyethylene. Conveniently, this next one will be solar heated.