Ōshimizu B and Sawairi B Sites, Shinchi Town, Fukushima Prefecture

Discovery of iron smelting furnaces of the Heian period

Ōshimizu B and Sawairi B are sites related to iron manufacture of the Heian period (mid-ninth century). Excavations were carried out there in 2012 in conjunction with construction of the Jōban Expressway, considered a vital road for the reconstruction.

The sites are located atop hills extending eastward from Mt. Karō in the Hamadōri region in eastern Fukushima prefecture, where furnaces for making iron using iron sand as ore were found.

Two types of smelting furnaces and a charcoal kiln

In the Ancient period there were two types of furnace, a chimney-shaped furnace resembling an overturned bucket, and a box-shaped furnace similar to a bathtub, and while there is held to be a chronological difference between the types, one characteristic of the northern part of Hamadōri region of Fukushima is the presence of both types in the same area and even at the same time, as at the Ōshimizu B and Sawairi B sites.

As pig iron, which is high in carbon content, was ascertained for both types of furnace, it is thought that the same quality of iron was being produced despite the difference in furnace type.

Also, a climbing kiln built in the form of a tunnel dug into a slope, with a firing chamber 5 m in length (9 m overall including the work area) and 1.5 m wide was found. This is thought to have been used as a kiln for making charcoal that was used as fuel in the smelting. In addition, pits where clay was quarried were found as well. (Yoshida//Hideyuki)

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