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The steel used in sword production is known as {{nihongo||玉鋼:たまはがね|[[tamahagane]]}}, or "jewel steel" (''tama'' – ball or jewel, ''hagane'' – steel). ''Tamahagane'' is produced from [[iron sand]], a source of iron ore, and mainly used to make [[samurai]] swords, such as the ''[[katana]]'', and some tools.
[[Image: Hi this is an editor of the wikepedia page, I just wanted to say this is very cool. Tatara steel making method NT.PNG|thumb|Diagram of a tatara and bellows]]The [[smelting]] process used is different from the modern mass production of steel. A [[clay]] vessel about {{convert|1.1|m|abbr=on}} tall, {{convert|3|m|abbr=on|0}} long, and {{convert|1.1|m|abbr=on}} wide is constructed. This is known as a [[Tatara (furnace)|''tatara'']]. After the clay tub has set, it is fired until dry. A charcoal fire is started from soft pine [[charcoal]]. Then the smelter will wait for the fire to reach the correct temperature. At that point he will direct the addition of iron sand known as ''satetsu''. This will be layered in with more charcoal and more iron sand over the next 72 hours. Four or five people are needed to constantly work on this process. It takes about a week to build the ''tatara'' and complete the iron conversion to steel. Because the charcoal cannot exceed the melting point of iron, the steel is not able to become fully molten, and this allows both high and low carbon material to be created and separated once cooled. When complete, the ''tatara'' is broken to remove the steel [[Bloomery|bloom]], known as a ''kera''. At the end of the process the ''tatara'' will have consumed about {{convert|9.1|t|abbr=on}} of ''satetsu'' and {{convert|11|t|abbr=on}} of charcoal leaving about {{convert|2.3|t|abbr=on}} of ''kera'', from which less than a ton of ''tamahagane'' can be produced.<ref>[http://www.hitachi-metals.co.jp/e/tatara/nnp01.htm The Tale of the Tatara]</ref> A single ''kera'' batch can typically be worth hundreds of thousands of dollars, making it many times more expensive than modern steels.<ref name="jsme">{{cite web|url=http://www.jsme.or.jp/tsd/ICBTT/conference02/TatsuoINOUE.html|title=International Conference|publisher=jsme.or.jp|access-date=2014-05-27}}</ref>
Japanese ''tatara'' steelmaking process using ironsand started in [[Kibi Province]] in the sixth century and spread throughout Japan, using a unique Japanese low box-shaped furnace different from the Chinese and Korean styles. From the Middle Ages, as the size of furnaces became larger and the underground structure became more complicated, it became possible to produce a large amount of steel of higher quality, and in the [[Edo period]], the underground structure, the blowing method, and the building were further improved to complete ''tatara'' steelmaking process using the same method as modern ''tatara'' steelmaking. With the introduction of Western steelmaking technology in the [[Meiji period]], ''tatara'' steelmaking declined and stopped for a while in the [[Taisho period]], but in 1977 [[Nihon Bijutsu Token Hozon Kyokai|The Society for Preservation of Japanese Art Swords]] restored ''tatara'' steelmaking in the Shōwa era and new ''tamahagane'' refined by ''tatara'' steelmaking became available for making Japanese swords.<ref name="tate2005">[https://web.archive.org/web/20220315073416/https://www.jstage.jst.go.jp/article/tetsutohagane1955/91/1/91_1_2/_pdf/-char/ja History of Iron and Steel Making Technology in Japan ーMainly on the smelting of iron sand by Tataraー.] Mitsuru Tate (2005). Tetsu-to-Hagane Vol. 91. The Iron and Steel Institute of Japan.</ref><ref name="yasuhis">[https://web.archive.org/web/20200929130900/https://tetsunomichi.gr.jp/history-and-tradition/tatara-history/part-1/ たたらの歴史 たたら製鉄の進歩 (Progress of Tatara Iron Making).] [[Yasugi, Shimane|Yasugi City]]</ref><ref name="yasuout">[https://web.archive.org/web/20211218202858/https://tetsunomichi.gr.jp/history-and-tradition/tatara-outline/part-1/ たたら」の発祥と発展 (Changes in Japanese Tatara Iron Making Technology).] Yasugi City</ref><ref name="nagoyata">[https://web.archive.org/web/20211106174529/https://www.touken-world.jp/tips/10863/ たたら製鉄の歴史と仕組み.] Nagoya Japanese Sword Museum Nagoya Touken World</ref>
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