Smeltery residue is a by-product of the smelting process, which involves heating metal ore to separate out the desired metal. The two main components of smeltery residue are DROSS (5 letters) and SLAG (4 letters). DROSS is a mixture of metal oxides and other impurities that float to the surface of molten metal, while SLAG is a non-metallic material that forms when impurities are removed from the molten metal.