Traditional Japanese weapons like a Nihonto and Wakizashi are made from a steel called tamahagane. The technology of tamahagane production came toJapanviaKoreaandChinaand is over a thousand years old.
You can translate is into Jewel-Steel (Tama-Hagane) or Jade steel. Tamahagane is made of Japanese Iron sand (fe) known as Satetsu.
The Satetsu is put in a Tatara, basicly a clay furnace. The Tatara is heated to a high temperature, about 1500 ºC and is mixed with charcoal to give tamahagane hardness.
The Tatara inJapanusually operates for +/- three weeks, one cycle taking seven days to complete. By the end of the process the walls of the tatara are torn down and steel called Kera remains. You can find High (nabe-gane) and Low (hocho-tetsu) carbon pieces Tamahagane in the Tatara after this process.
On this picture you can find a piece made in the Nittoho Tatara in Shimane, Japan.
You can find this piece Tamahagane in my shop so people can take a look.