GeoPark Kaolinrevier Hirschau
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InfoPoint No. 4

 

The forest, the quarrying of mineral ore and the smelting of iron in Eastern Bavaria in prehistoric and primeval times

The dating of iron slag has revealed that iron smelting began in Eastern Bavaria in the late La Tène period (150 - 50 B.C.).
The iron ore was smelted where it was quarried, as is proved by numerous sites in the Regensburg-Kelheim-Parsberg region.

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Illustration: Painten Forest near Kelheim, early 17th century. The map shows ore mines ( the ore was extracted by means of hand-winches), charcoal piles and smelting sites with slag heaps. The small pieces of ore were smelted on the spot. The so-called bloom produced in the smelting process (a lump of iron consisting of iron particles fused with other substances and with charcoal) was then taken to forges to be wrought.

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Illustration: Shaft in Frauenforst near Kelheim. The circular shaft with no wooden lining has a diameter of 80cm. The shafts were excavated as far as the stratum containing the ore, which was then extracted. They were fi lled up again, probably using spoil from neighbouring shafts.

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Illustration: Funnel-shaped pit in Frauenforst near Kelheim. The earthen wall around the circular funnel is typical. Funnel-pits like this are also to be found in the Theuern and Wolfsbach area.

After smelting had fi nished, the bloomery (i.e., the furnace) was broken open and the inhomogeneous lump of iron (bloom) was removed. The paste-like mass was then consolidated and forged. The slag component was beaten out under pressure and at a higher temperature and, after the remainder had been heated up again and carbon added, the product was malleable iron with a low carbon-content, which could then be wrought.


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Illustration Reconstruction of a shaft furnace in the Franconian Jura district, in which forgeable iron can be produced from iron ore in a single process. Celtic smelting sites have been discovered in large numbers in Sopron/Ödenburg in Hungary, in Burgenland in Austria, and also, for example, in Kelheim in Bavaria. They had clay furnaces up to a metre in height. Presumably, these furnaces sometimes had an ashlar sheath to ensure greater stability. The furnace was fi lled with alternate layers of charcoal and iron ore. The air supply, generated by means of bellows, was introduced into the lower part of the furnace through ceramic tuyeres or nozzles. Foot-operated bellows for providing the air supply at shaft furnaces in the Upper Palatinate are mentioned as early as 1285. The smelting process took place at relatively low temperatures of 1200-1300° Celsius (the melting point for iron is 1528° Celsius!). The slag drained off, leaving a sintered mass consisting of metallic iron.

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Illustration: Excavations in Frauenplatz in Amberg revealed up to 2-metre deep layers of iron slag, mixed with ceramic tuyeres (or nozzles) and shards dating from the 11th and 12th centuries. This showed, for the fi rst time, that iron was being smelted in Amberg at that early period.