Alloying can be effected via the addition of the element, e.g. lump silicon for Al-Si alloys, or an alloy, e.g. ferrosilicon for Al-Fe-Si alloys, or via the flux, e.g. titanofluorides, or borofluorides for titanium and boron alloys, which are particularly important in grain refining applications. ‘Irony scrap’, that is aluminium scrap which contains ferrous parts sucg as nuts and bolts, is melted in reverberatory furnaces with slopping hearths.