Bloomery
These pipes, called tuyeres, allow air to enter the furnace, either by natural draught or forced with bellows or a trompe.
The desired particle size depends primarily on which of several ore types may be available, which will also have a relationship to the layout and operation of the furnace, of which a number of regional, historic/traditional forms exist.
Intentionally producing blooms that are coated in steel (i.e. iron with a higher carbon content) by manipulating the charge of and air flow to the bloomery is also possible.
Recent evidence, however, shows that bloomeries were used earlier in ancient China, migrating in from the west as early as 800 BC, before being supplanted by the locally developed blast furnace.
[3] The earliest records of bloomery-type furnaces in East Africa are discoveries of smelted iron and carbon in Nubia in ancient Sudan dated at least to the seventh to the sixth century BC.
Smelting in bloomery type furnaces in West Africa and forging of tools appeared in the Nok culture of central Nigeria by at least 550 BC and possibly several centuries earlier.
[7][8][6] The site of Gbabiri, in the Central African Republic, has also yielded evidence of iron metallurgy, from a reduction furnace and blacksmith workshop, with earliest dates of 896–773 and 907–796 BC, respectively.
[6] During a hydroelectric plant project, in the southern foothills of the Central Highlands, Samanalawewa, in Sri Lanka, a wind-driven furnace was found in an excavation site.
These ancient Lankan furnaces might have produced the best-quality steel for legendary Damascus swords as referred in earlier Syrian records.
[11] Early European bloomeries were relatively small, primarily due to the mechanical limits of human-powered bellows and the amount of force possible to apply with hand-driven sledge hammers.
Those known archaeologically from the pre-Roman Iron Age tend to be in the 2 kg range, produced in low shaft furnaces.
[12] Contemporary experimenters had routinely made blooms using Northern European-derived "short-shaft" furnaces with blown air supplies in the 5–10 kg range [13] The use of waterwheels, spreading around the turn of the first millennium and used to power more massive bellows, allowed the bloomery to become larger and hotter, with associated trip hammers allowing the consolidation forging of the larger blooms created.
Even when applied to a noncarburized bloom, this pound, fold, and weld process resulted in a more homogeneous product and removed much of the slag.
[16][17] In England and Wales, despite the arrival of the blast furnace in the Weald in about 1491, bloomery forges, probably using waterpower for the hammer and the bellows, were operating in the West Midlands region beyond 1580.
[21] Bloomeries survived in Spain and southern France as Catalan forges into the mid-19th century,[22] and in Austria as the Stückofen [fr] to 1775.
[23] The cluster of Viking Age (c. 1000–1022 AD) at L'Anse aux Meadows are situated on a raised marine terrace, between a sedge peat bog and the ocean.
The archaeology at Jamestown Virginia (circa 1610–1615[citation needed]) had recovered the remains of a simple short-shaft bloomery furnace, likely intended as yet another "resource test" like the one in Vinland much earlier.
The English settlers of the Thirteen Colonies were prevented by law from manufacture; for a time, the British sought to situate most of the skilled artisanry at domestic locations.
