Plans for a gas smelting furnace include a homemade gas-fired scrap metal smelting furnace and instructions on how to construct one. You will learn how to construct your own gas-fired smelting furnace by following these plans. You can melt gold, silver, aluminum, brass, and copper with this small furnace; prepare thin, small pieces of steel and iron for brazing or forging by heating them; make soft steel casehardened; bake vitreous enamels on metals and make alloys. Gas from a city or LP can be used. The refractory lining: Build the refractory lining inside a sheet-metal can from 11-1/2 to 14in. in diameter, and from 14 to 17 in. high.