Uploaded March 2018 | Updated September 2026, 3 days ago
Yakiire - Differential hardening a classical style sunnobi tanto blade forged from century-old reclaimed shear steel. Sunnobi tanto are larger than ordinary tanto (nagasa above 1shaku) and may have sori similar to ko-wakizashi.
see the whole process of forging this tanto here: islandblacksmith.ca/2018/03/utsushi-study-of-a-sunnobi-tanto
1. Using approximately a 1:1:1 mixture of natural clay, polishing stone powder and ground charcoal to mask the back of a hand forged blade about 1-1.5mm thick to slow down the cooling rate.
2. Brushing on a thin slip layer with extra charcoal added along the exposed edge to speed up the cooling rate and protect from carbon loss.
3. Carefully heating in a charcoal forge supplied by air from a fuigo box bellows until the edge reaches critical temperature.
4. Plunging edge-first into cold rainwater to cool the blade quickly and harden the edge while leaving the rest tough and resilient.
5. Testing for successful hardening with a file and then removing the clay with a mild steel scraper.
6. Slightly reheating the blade over the flames to temper the edge.
7. Test polishing on a coarse Japanese waterstone to check the hamon.
more about the process: islandblacksmith.ca/process
more about yaki-ire: islandblacksmith.ca/process/yaki-ire-clay-tempering
Yakiire - Differential hardening a classical style sunnobi tanto blade forged from century-old reclaimed shear steel. Sunnobi tanto are larger than ordinary tanto (nagasa above 1shaku) and may have sori similar to ko-wakizashi.
see the whole process of forging this tanto here: islandblacksmith.ca/2018/03/utsushi-study-of-a-sunnobi-tanto
1. Using approximately a 1:1:1 mixture of natural clay, polishing stone powder and ground charcoal to mask the back of a hand forged blade about 1-1.5mm thick to slow down the cooling rate.
2. Brushing on a thin slip layer with extra charcoal added along the exposed edge to speed up the cooling rate and protect from carbon loss.
3. Carefully heating in a charcoal forge supplied by air from a fuigo box bellows until the edge reaches critical temperature.
4. Plunging edge-first into cold rainwater to cool the blade quickly and harden the edge while leaving the rest tough and resilient.
5. Testing for successful hardening with a file and then removing the clay with a mild steel scraper.
6. Slightly reheating the blade over the flames to temper the edge.
7. Test polishing on a coarse Japanese waterstone to check the hamon.
more about the process: islandblacksmith.ca/process
more about yaki-ire: islandblacksmith.ca/process/yaki-ire-clay-tempering
