Blister Copper: Matte Blown in a Quartz-Lined Converter (Parrot Works, Butte, Peters 1905)

Air blown through molten matte burns its iron and sulphur: first the iron goes into a slag with the silica of the converter's quartz lining, then the sulphur leaves the copper sulphide and metallic copper remains. Result: blister copper of up to over 99 %, poured in pigs of 215 to 275 lb; a 55 % matte took about 39 minutes to slag and 44 minutes to make copper. Source: Edward D. Peters, Modern Copper Smelting (1905), ch. XVII, Parrot practice; picture: his Plate XVI, converters. Not given: the remelting cupola charge. The blow gives off sulphur dioxide, a poisonous gas.