BLOWPIPES VERSUS BELLOWS IN ANCIENT METALLURGY

In the smelting of ores and the melting of metals during antiquity, the oxygen necessary for the combustion of the charcoal fuel was supplied by human breath through blowpipes; by ambient air via bellows; or, less frequently, by ambient air by natural draft. Because of its chemical composition, however, human breath is limited in both the maximum temperature attainable and in the amount of heat that it can generate in combustion; furthermore its rate of supply is constrained by the physiology of the human body. The result is that the metallurgical capabilities of blowpipe furnaces are limited to the smelting of ores of copper in quite small furnaces. An analysis is given of the operation of a copper smelting furnace excavated in Peru. Ambient air supplied by bellows to a charcoal fueled furnace can develop the higher temperatures necessary to smelt iron ores, and one person can then generate heat at about 70 times the rate that he can develop if using a blowpipe. Implications of the much greater metallurgical utility of bellows-driven air are that bellows would be used in preference to blow-pipes for all metallurgical purposes as soon as they were available; that ambient air is necessary for the smelting of iron ores; and that patterns of bellows use in antiquity and of iron smelting may be similar.