An ancient metallurgist had at his disposal material that was steel from a chemical point of view, thus an alloy of iron and coal, as the term iron refers actually to a chemical element. The term iron is also used when an alloy has not gone through a liquid stage in the process but turned into a doughy form at the most, thus the spongy iron from pit furnace is defined in this way too. The steel as we know it in modern times has an almost homogeneous structure and chemical constitution and its properties depend mostly on the content of coal and other alloy ingredients as well as on the applied thermal treatment (hardening).

Historical steel, iron in other words, has a banded, fibrous structure of a heterogeneous chemical constitution. It is the result of welding small pieces of iron as obtained in its doughy form and of different chemical constitution.


FIBROUS STRUCTURE OF HISTORICAL IRON EXPOSED IN THE PROCESS OF CORROSION

It is highly improbable that from every smelting a large metal billet weighing up to several kilos was obtained. Most probably these were numerous smaller pieces of rectangular or cigar shapes and the weight of several hundred grams so sufficient to make the majority of iron objects then used.


SPONGY IRON PIECE OBTAINED BY WELDING OF CONTAMINATED IRON SPONGE (RECONSTRUCTION).