Quote Originally Posted by Frivolous248
Are you making a gravity bong? I used to go out in the garage and find a small socket, then melt it into the top of a bottle cap, works great. But I couldn't find any last time, so now my grav-top is just the end of a laser-pointer cap. Just find any small piece of metal laying around and it will work.

Also, tin foil would be fine if you could rig it up right.
The cap of my bottle isn't flat, its slightly curved. I found a small piece of copper piping, so I wrapped foil round one end, put holes through with a needle, then place it firmly on the cap, put the weed in, then light it and let the bottle rise....