Japanese sword (nihontō) of tamahagane steel
Espada japonesa (nihontō) de acero tamahagane
- Date
- c. 900-1000 · confidence low
- Place
- Osafune, Setouchi, Okayama (old Bizen), Japan
- Credited to
- Heian-period sword smiths
- Field
- Conflict
⚠️ Disputed: the sources disagree.
What it is
A curved blade forged from tamahagane steel produced in tatara furnaces, folded and combined with a softer core, and hardened with clay to give a very hard edge and a flexible spine. Differential hardening leaves a visible line (hamon) and produces the characteristic curve.
The transition from the straight sword to the curved tachi is placed at the end of the 10th century, without an exact date. The current tatara furnace was perfected in the Edo period.
What it led to
- the samurai katana
- the forging schools of Bizen, Yamashiro and Sagami
- the metallurgical study of differential hardening