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Thetatara (鑪) is a traditionalJapanesefurnace used forsmeltingiron andsteel. The word later also came to mean the entire building housing the furnace. The traditional steel in Japan comes fromironsand processed in a special way, called the tatara system.[1]
Iron ore was used in the first steel manufacturing in Japan. Tatara steelmaking process using ironsand was conducted in theKibi Province, which later became the base of theBizen school of swordsmithing, around the middle of the sixth century, and steelmaking using ironsand is thought to have spread from Kibi to various places in Japan. In western Japan, a low box-shaped furnace different from the Chinese and Korean style was used to refine iron, and in eastern Japan, both a low box-shaped furnace and a vertical furnace unique to Japan were used.[2][3][4][5]
In the Middle Ages, furnaces were enlarged to produce more steel of higher quality, and underground facilities were also huge and complicated to keep the furnace warm and reduce humidity. In addition, a new method of collecting ironsand, calledkanna nagashi (鉄穴流), which can efficiently collect more ironsand using waterways, was adopted.[2][3][4][5]
In theEdo period, tatara steelmaking was further improved and became the same as today's tatara steelmaking in Japan. Tatara steelmaking came to be carried out in a stereotyped building calledtakadono (高殿), and a space calledHondoko (本床), where charcoal is laid, and a space calledKobune (小舟), which has a tunnel-like gap, were installed under the steelmaking furnace, completing the underground structure known asHondoko zuri (本床釣り). In the late 1600s, tatara steelmaking adopted a revolutionary invention. It is a foot-operated blower called atembin fuigo (天秤鞴), which can blow a large amount of air into the furnace to increase the temperature. As a result, high quality steel can be produced in large quantities.[2][3][4][5]
By 1920, Tatara Furnaces were no longer economically viable and they closed once the Western blast furnace was introduced to Japan. In 1977, theSociety for Preservation of Japanese Art Swords and historical firearms (Nihon Bijutsu Token Hozon Kyokai) with the approval of the Japanese government's department of the environment built a tatara furnace to makeJapanese swords.[2][3][4][5]
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Tamahagane (玉鋼) is a general term for steel, not used prior to the Meiji Era, literally meaning "precious steel". Steel is smelted at Shimane facility forJapanese swords (nihontō (日本刀), commonly known askatana (刀)) by contemporary Japanese forge masters like Kihara Akira and Gassan Sadatoshi is still smelted in atatara. One of the few remainingtatara is the Nittohotatara inShimane Prefecture, Japan.
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The term 'tatara' first appeared inKojiki compiled in 712 asHototarara Isusukihime no Mikoto (富登多々良伊須々岐比売命) and inNihonshoki compiled in 720 asHimetatara Isuzuhime no Mikoto (姫蹈鞴五十鈴姫命), and these words representShintokami. Historically, severalkanji characters have been used to express the term 'tatara,' and in ancient times, '蹈鞴', which represents a fan, was used, and as time went by, '鑪', which represents the whole steel works, and '高殿', which represents the buildings of steel works, were also used. Today, the term 'tatara' is applied to steelmaking technology using ironsand, which flourished from ancient times to the Edo period.[4]
Thesmelting process used differs from that of the modern mass production of steel. Aclay vessel about 1.1 meters (3.6 feet) tall, 3 meters (9.8 feet) long, and 1.1 meters (3.6 feet) wide is constructed. This is thetatara. After the clay tub has dried, it is fired until dry. A charcoal fire is started from soft pinecharcoal, then the smelter will wait for the fire to reach the correct temperature. At that point, he will direct the addition ofironsand, known assatetsu. This will be layered in with more charcoal and more ironsand over the next 72 hours. Four or five people need to constantly work on this process.
It takes about a week to build thetatara and complete the iron conversion to steel. When the process is done, the clay tub is broken and the steel bloom, known as akera, is removed. At the end of the process, thetatara will have consumed about 9.1 t (9.0 long tons; 10.0 short tons) ofsatetsu and 11 t (11 long tons; 12 short tons) of charcoal, leaving about 2.3 t (2.3 long tons; 2.5 short tons) oftamahagane.
In 1977, the Japanese Society for Preservation of Japanese Art Swords (Nittoho), together with the Japanese government's Agency for Cultural Affairs and Hitachi Works subsidiary Yasugi Special Steel, built inShimane Prefecture the so-named NittohoTatara to provide the steel necessary for the production of Japanese swords and historical firearms. The NittohoTatara is managed by Yasugi Works, and is operational only during the winter months.
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