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How to make Japanese sword / No.4

==> How to make a Japanese sword No.3

After SHIAGE the blade is coated with YAKIBA-TSUCHI(adhesive clay mixture).


The part coated with thin cray is cooled rapidly and hardened. The part coated with thick cray is cooled slowly and remains its softness.
By that hardness defference HA-MON rises to the surfaces of the blade after grinded.


9.YAKI-IRE(Hardening the Edge

YAKI-IRE is performed at night or at noon within the workshop darkened.
I do this process after dark, because my workshop doesn't have darkening equipment.
The blade is heated to a latter half of 700-900 degrees C, then cooled rapidly with water. Because this both temperature are very important, we do the process in the dark for recognizing the temperature of the blade by colour. As soon as the heated brade is plunged into a water, quenched edge part is hardened quickly and back side is cooled slowly and shrinks. As a result of this phenomenon SORI(measure of curvature) comes out.


For that reason I figure out how much SORI comes out in YAKI-IRE and give curvature to the brade in HI-ZUKURI, and that adjustment makes appropreate SORI.
At YAKI-IRE failing temperature control causes problems. Too low temperature could not harden the edge. Too high temperature might also make HA-GIRE(cracks in the blade).


Checking HA-MON and shaping the brade while polishing

Decorative carvings is done on the ridge side(not hardened). At first a draft is sketched with checking balance, then carvings are done into the brade with chisels.
SHITA-E(a draft)
ARA-BORI(rough carving)

The NAKAGO(tang) of Japanese sword is given a decorative file pattern and inscribed the MEI(smith's name). There are all kind of file patterns and each swordsmith has kis own stamp.
MEI with grass character
MEI with standerd style
Usually swordsmith inscribes MEI with using a chisel and hammer but sometimes MEI-KIRI-SHI(a specialized technical expert who act for inscribing) has also inscribed MEI instead of the smith. I heard that there is a MEI-KIRI-SHI who is still living in Seki, unfortunately I haven't met him yet.

==> How to make a Japanese sword No.5