When I was a kid I used to do this with propane. I'd fill it with a propane torch - which is set t mix the C3H8 and O2 to the right proportion - and light it. I

When I was a kid I used to do this with propane. I'd fill it with a propane torch - which is set t mix the C3H8 and O2 to the right proportion - and light it. I would not use a restrictor/nozzle cap because it had plenty of thrust without it. I survived my childhood unscarred, somehow.