...a long time ago, in a county far, far away... a local welder made a woodburner for me out of an old gas bottle - he filled it with water first and boiled it over a fire. "Gas has bonded with metal", he said. Then he chopped off the top, welding on a big flat plate and collar for a flue, then constructed a sliding door on the side, to control temperature. Quite honestly, it was the best wood burner I have ever owned. Even during the coldest winter escapes, I had to keep the windows of my caravan open, because it was too hot. The bottom of gas bottles thin out eventually, as metal heats and bends... but as far as I know, the chap who bought the caravan and woodburner from me, is still using it.