The Charm of the Japanese Sword
We cannot help but feel a sense of purity in the fact that the Japanese sword, despite being created to serve as a tool, possesses beauty as well.
Furthermore, each Japanese sword has its own unique curvature (sori), shape, and blade pattern (hamon). When one observes them closely, they feel a corresponding surge of emotion and are naturally drawn in, which is where their charm lies.
Production Process
01Charcoal Cutting
The pine charcoal used by swordsmiths is easy to ignite and light, making it easy to put the steel in and take it out.
The stick-shaped pine charcoal is cut into 3cm squares with a hatchet.
Since the heat power will not be uniform if the cut charcoal pieces are not the same size, it is important to cut them carefully.
02Water Pressing/Quenching
The tamahagane (jewel steel) is heated and hammered thin until its thickness is about 5mm, then it is immediately quenched in water while still hot.
03Breaking and Sorting
The quenched tamahagane hardens and can be easily broken by tapping it on an anvil.
The finely broken pieces are sorted into hard steel with high carbon content (for Outer Steel – Kawagane) and soft steel with low carbon content (for Core Steel – Shingane).
04Stacking and Welding
The sorted hard steel (for Outer Steel) is stacked on a base made of tamahagane, wrapped in Japanese paper, sprinkled with straw ash, and coated with clay slurry.
Heating this process creates a glass-like surface, preventing the direct blast of air onto the steel and allowing the core to be heated to a uniform temperature.
The soft steel (for Core Steel) is treated similarly.
05Folding and Forging
The stacked and welded steel is heated, forge-welded, stretched into a rectangular shape, cut in the center, and folded over.
This forging process is repeated about 15 times for the hard steel (Outer Steel) and about 6 times for the soft steel (Core Steel).
06Structuring/Enclosing
The forged hard steel (Outer Steel) is shaped into a U-shape, and the forged soft steel (Core Steel) is shaped into a simple blade shape (or a rectangular bar).
The Core Steel is inserted into and forge-welded with the Outer Steel.
07Rough Forging and Shaping
The structured steel is stretched into a rod shape (Sunobe – rough forging), and then the blade edge is hammered out using only a hand hammer to forge the sword into a smooth, even shape (Hizukuri – shaping by fire).
08Rough Finishing
Tools such as files (yasuri) and scrapers (sen) are used to shape the Hizukuri steel.
It is then meticulously finished with coarse whetstones to complete the approximate shape of the sword.
09Clay Application
Yakibatsuchi (quenching clay) is made by mixing clay with charcoal and whetstone powder. First, a thin layer of clay is applied to the area that will become the hamon (blade pattern).
Then, ashizuchi (foot clay) is placed on top, and a thick layer of clay is applied to all areas other than the blade pattern.
The pattern of the hamon is determined by how the Yakibatsuchi is applied.
10Quenching
Once the applied clay is dry, the entire blade is heated uniformly.
When it is judged to have reached 780°C, the blade is rapidly cooled by placing it in a water tank. Quenching changes the expansion rate between the edge side and the back side (mune), causing the sword’s curvature (sori) to appear.
Accurately judging the heating condition of the entire long sword from a vertical perspective is an exceedingly difficult feat (or an extremely challenging endeavor).
11Correcting Distortion
The distortion of the blade is removed, and the entire blade is cleaned and polished to prepare it for final refinement.
12Craftsmen and Engraving the Signature
The blade, having undergone Kaji-oshi, is then passed through the craftsmen—the polisher (togishi), the metal fitting specialist (shiroganeshi), and the scabbard maker (sayashi).
Once the swordsmith is convinced that the work can be delivered to the customer, the signature (mei) is engraved with a chisel, marking the completion.