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From Value One, Winter 2006-2007 No. 15  

Okuizumo Town, Shimane Prefecture, is responsible for passing down Japan's ancient Tatara iron making method to the present day. Steel of high purity can be manufactured from iron sand using this unique Japanese technique, which was established in the sixth century (during the latter part of the Kofun Period in Japan) and is still practiced today.

 

Tatara is carried out a few times a year between January and late February. This is the only place in the world where the mass production of steel using iron sand takes place.

A Tatara process begins with the creation of a clay furnace. The furnace is boat-shaped, measures 1.0 m wide, 2.7 m long and 1.2 m tall, and its wall is more than 50 cm thick at the maximum. Charcoal is put into the furnace and a fire is lit. When the furnace is hot enough to melt the iron sand, the murage (person in charge of the Tatara) gives the command to add the iron sand. Charcoal and iron sand are alternately added at 30-minute intervals. This is repeated for three days and nights. During this time, the murage remains awake and concentrates on controlling the flames. He watches the color of the rising flames, checks the inside of the furnace through a peep window known as a hodo-ana, and listens to the sound of the iron sand melting and transforming into a steel ingot called a kera.

The furnace is built in this building for Tatara operations.



Masa, iron sand almost free of impurities such as phosphorus and sulfur, is put into the burning furnace.



Steel that has a carbon content of less than 1.85%, known as tamahagane, is used to forge traditional Japanese swords. Three tonnes of kera yields approximately 2.3 tonnes of tamahagane.

During a full Tatara operation, about 13 tonnes of charcoal and 10 tonnes of iron sand are used. The charcoal reduces the amount of oxygen in the iron sand, which then melts and turns into a kera on the furnace floor. In the process, the iron sand erodes the furnace wall and is transformed into steel of even higher purity through chemical reactions with the minute contents of the clay. About 70 hours after the process begins, the furnace is demolished. Every time a part of the furnace wall collapses, sparks shoot up, and approximately three tonnes of smoldering dark red kera can be seen. This is the moment when the process of creating iron from clay, sand and flames is complete.

Okuizumo Tatara & Sword Museum
1380-1 Yokota, Okuizumo-cho, Nita-gun, Shimane
Tel: +81-854-52-2770
Open: 10:00 to 17:00
Closed on Mondays, during the year-end and New Year holidays
Admission: ¥510 for adults, ¥250 for elementary school and junior high school students



The Okuizumo Tatara & Sword Museum is dedicated to the history of Okuizumo Town and Tatara. An exhibited full-size model of a Tatara furnace illustrates how the iron sand transforms into steel. A demonstration of the process of forging a traditional Japanese sword is also provided.

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