The furnace is charged with slag, scrap iron, limestone, coke, oxides, dross, and reverberatory slag. Wrought iron was a soft material that contained slag or "dross". An inclusion is a metal contamination of dross, if solid, or slag, if liquid. These oxides are removed with the dross while cleaning the surface of the molten metal. This process results in molten lead and dross. Regeneration-metal was melted into the crucible to replace lost tin and antimony through the dross. Solder, product waste and dross may also be recovered for its small lead content. The resulting bismuth dross can be skimmed off. At intervals the lead is remelted and the oxidized metal (dross) skimmed off. Aluminium dross recycling is a completely different process to strictly aluminium recycling. If floating, dross can also be skimmed off. Recycling aluminium dross mechanically is an environmentally sensitive method, and is not toxic. He recognizes the refined essence and discards the dross. Wrought iron was soft and contained flaws caused by included dross. An aluminium stack melter produces significantly less dross, with values reported below 1%.