Keys to the Past


Bloomery; Bloomeries

An early form of furnace for smelting ironstone. They are so named because a bloom of varying Iron (Fe) and Steel (Iron and Carbon, C) was produced as the ironstone never reached the melting point of Iron (1540°C). Such a furnace would be a 1.0m high circular clay wall into which ironstone and charcoal were added at the top. A fire would be started at the base, and the fuel and ironstone added. Air would be blown in to fan the fire. A liquid slag could be 'tapped' from the base of the furnace to run, like lave, before solidifying. The Iron bloom was removed by taking away part of the walls.

Bloomeries date from the Iron Age and lasted till near the end of the Medieval period in varying numbers, though some later Post-Medieval examples may have survived for small ad hoc use. An intermediate stage between the bloomery and the blast furnace was the high bloomery. The process was not particularly effective with a ton of Iron to several tons of ironstone and fuel. Some blast furnaces used bloomery slag. Where slag remains this may be the sign of a bloomery.

The term can be used generally for all the iron-smelting site which would have included hearths for roasting ironstone, ironstone and fuel stores, and buildings that covered the furnace and acted as workers accommodation.

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