The Knife Production Process
The finest craftsmen work to fashion CHOYO and KIKUZUKI by hand from forging to sharpening. The true character of the steel is drawn out to the greatest degree possible, giving rise to an overwhelming sharpness. The quality of this craftsmanship also appears in the ease of maintenance. These unwavering blades almost seem to stick to the whetstone, making sharpening easy, and only a little time spent at the whetstone brings back a fine edge.＊ The following explanation is an outline. A different process is used for Yasugi Silver #3.
- Steel Welding
Yasugi Steel and a soft iron—two metals with different properties—are welded.
The blade is heated in the furnace and hammered repeatedly to forge the Yasugi Steel and base metal to one another.
During yakinamashi, or annealing, the blade is left to cool slowly for 24 hours in the ashes of rice straw, giving it a uniform composition.
- Cold Forging
The blade is hammered repeatedly again at room temperature to complete the forging process.
Unnecessary steel is lopped off to give the knife its shape.
During yakiire, or quenching, the blade is heated to around 800°C by burning pine charcoal, and then immediately cooled in water to harden the Yasugi Steel.
Pine charcoal is highly suitable to yakiire, as it has very little sulfur and therefore does not affect the properties of the steel.
During yakimodoshi, or tempering, the blade is once again heated to around 170°C, creating a durable blade that is difficult to chip or nick.
- The Knife Base
The knife base produced by the forging process.
During aratogi, or rough sharpening, the blade is sharpened to create its general shape.
The flat surface of the knife is sharpened during hiratogi, determining the thickness of the knife.
During hontogi, the cutting edge and back side of the knife are honed to give an edge to the blade.
A kido, or wooden whetstone, is used to give a matte finish to the surface of the edge of the blade, producing a dignified appearance.
- Mirror Polishing
During the mirror polishing process, the flat surface of the knife is polished even further.
YASUGI SPECIALTY STEELS
YASUGI SPECIALTY STEEL (YSS) is a high-grade cutlery steel made at the Yasugi Metal Works of Hitachi Metals. It is very pure and ideally suited for use in the creation of Japanese knives, which have inherited the traditions of Japanese steel working. There are several types, such as white, blue, and silver, each with their own characteristics.
- YSS White #2
Combining hardness and durability, this steel provides an exceptionally sharp edge. It has a soft feel when being sharpened and is easy to care for.
- YSS Blue #1
Boasting a high degree of hardness, this steel maintains a smooth sharpness. It requires some experience to sharpen it well.
- YSS Silver #3
While resisting rust, this stainless steel carries a fine sharpness. A special whetstone for use with this steel is available for purchase.