Bloomery Iron

 

 

What is historical steel?

Modern steel in today's production and manufacturing does have undeniable benefits, but for the classicly working blacksmith they can not always be the best material. Due to the industrial production and composition - not to compare with historical steels - for example a proportion of scrap (a mixture of different materials) is used. Even today, the purest steels are produced in traditional clay ovens made from the best iron ore, using high grade charcoal: for example the Tatara process in Japan or in the context of experiments on the historic iron and steel production. In European trade this material does not appear on the market, self-production is the only way.

As a region with a long history of iron production, the Westerwald gives a great variety of information and raw materials for production of authentic material for replica of historical weapons and tools.

How is steel made?

As the Bronze Age methods have been developed for smelting ores in the clay oven, based on that knowledge, the new materials could be obtained. However, since the temperatures obtained for the reduction of ferric oxide in the ore are higher than those necessary for copper/bronze production - from about 1000 degrees Celsius - the usual stoves had to be adjusted at the beginning. Also they were built with higher and thicker walls, better insulated against heat loss. In the bloomery process the iron oxide from the ore will get reduced to iron. For a professional bladesmith, iron is less attractive compared to steel. Driving the Bloomery Oven on a higher temperature –up to 1400°C- will add some of the carbon from the charcoal to the iron and give a carbon steel bloom.

 


The construction

The oven was built of clay, a willow or hazel mesh was smeared with clay, mixed with chopped straw and fine sand. In the lower range often stones were set up to give a foundation.

Structurally at least one wind hole for the oxygen supply to the fire and a opening for the tapping of molten rock and clay (slag) is necessary. Reconstructions of the early Iron Age furnaces produce a lower wall thickness up to 45 cm with a total maximum height of the chimney about 160cm. In the reconstructed templates, the diameter at the bottom of the furnace about 30cm, at the chimney orifice above about 20. In these compositions, a chimney effect is not sufficient, so that the use of bellows is suspected.

Seminars:

The Wollschmiede organizes bloomery seminars for small groups on request. Part of the workshop is: selecting raw materials, classifying of the bloom, purifying and homogenizing of the steel.