Hazuya and Nugui: The Sword Polisher's Final Finishing Techniques

Two-Stage Structure of Japanese Sword Polishing

Japanese sword polishing is broadly divided into two stages: "shitaji togi" (foundation polishing) and "shiage togi" or "keshou togi" (finish polishing). Foundation polishing is a process that shapes the blade, removes rust and scratches, and accurately polishes out each surface such as the shinogi (ridgeline), flat side, spine, and crosspiece. Finish polishing further refines the surfaces prepared through foundation polishing and brings out the characteristics of the jigane (the steel pattern and reflection) and the detailed aspects of the hamon (such as nie, nioi, kinsuji, and inazuma) to a state worthy of appreciation.

In the work of a togishi (sword polisher), foundation polishing has technical precision (geometric accuracy of the surfaces) as the primary evaluation standard, whereas finish polishing is a "display technique" for maximizing the individual character of the sword, and the aesthetics and experience of the togishi become critically important.

Types of Whetstones Used in Foundation Polishing

Polishing proceeds sequentially from coarse whetstones to fine whetstones. A representative usage sequence is as follows:

• arato: Coarse whetstones equivalent to 80–120 grit. Used for rust, scratches, and erasing marks from previous polishing. Blade shape correction also occurs at this stage.
• nakato: Equivalent to 240–400 grit. Erases the marks from the rough stone while increasing flatness.
• komato: Equivalent to 600–1,000 grit. The stage where the shinogi and flat surfaces become refined.
• uchigumori-do: Known as "Kyoto-produced uchigumori," considered the highest quality natural whetstone. The fine particles on the surface create an even cloudlike finish, and the jihada (steel pattern) of the jigane becomes visible. Used in the final stage before finish polishing.

Core Processes of Finish Polishing

Uchi-gumori

Thin pieces of uchigumori whetstone are pasted onto paper (shoji paper or washi) to create "nugui-gami-do" (wiping paper whetstone), which is then used to carefully polish the jigane (the flat side, shinogi area, and spine). Through this process, the jigane achieves an even cloudlike finish, and the structure of the jihada (such as itame, masame, and mokume patterns) floats into view and becomes appreciable.

The difficulty of uchi-gumori lies in the fine adjustment of pressure and speed. If the force is too strong, the cloudlike finish becomes uneven; if too weak, the particles from the uchigumori whetstone do not transfer sufficiently. The togishi makes fine adjustments for each part while monitoring the sensation in the fingertips and the changes in the reflected light off the blade.

Hatori and Hazuya

The process of emphasizing the hamon (edge line) from the hamachi (edge corner) to the kissaki (point) is called "hatori" (edge definition). In hatori, in contrast to the cloudlike finish of the jigane, the nie, nioi, kinsuji, sunagarashi, and other aspects of the hamon are finished to be bright and lustrous.

The whetstone used is called "hazuya" and consists of small natural stone pieces with extremely uniform particles and high hardness. It is distinguished by production region such as "Tsushima-san" or "Tanba-san" and is chosen according to the characteristics of the hamon (whether it is niede or nioideki).

Through hatori, a contrast emerges between the "cloudlike" quality of the jigane and the "lustrous" quality of the hamon, and this contrast becomes the essence of the appreciative beauty unique to Japanese swords. When an aristocrat from the Heian period composed, "A sword takes clouds on the jigane and light on the edge," this referred to this aesthetic contrast.

Yubi-kakari or Nugui

As the final stage of finish polishing, there is a process called "finger polishing" where the togishi uses their own fingernails or fingertips to make final adjustments to the junctions of the spine, shinogi, and flat side (shinogi line and spine corner). This technique, which uses the togishi's own body as the polishing material rather than whetstones, is the final adjustment process for removing minute irregularities and polishing unevenness.

As a material used in finger polishing, besides nails, some togishi use extremely fine-grained natural stone thinly sliced and pasted onto the fingertips, called "hadado" (skin stone). The final surface uniformity depends on the precision of this process.

Whetstone Selection Logic

The selection of whetstones used in finish polishing varies depending on the style of the sword, the characteristics of the jigane, and the type of hamon.

• Niede swords (Soshu tradition, Late Koto-period swords): To emphasize the large particles of nie, a somewhat softer hazuya with coarser particles is effective. Excessively hard whetstones risk crushing the nie.
• Nioideki swords (Bizen tradition, Yamashiro tradition): To avoid erasing the fine nioi particles, uniform and fine-grained uchigumori and hazuya are used. Excessive polishing can cause the depth of the nioi to be lost.
• Jihada patterns (itame, masame, mokume): Old swords with widely-spaced itame are prone to having their jihada emphasized through uneven uchi-gumori. Yamashiro-tradition swords with flowing masame require even cloudlike finish to be important, and the quality of the uchigumori with uniform particles determines the evaluation.

Togishi Qualifications and Modern Training

To become a togishi (sword polisher), organizations such as the Bijutsu-to-ken Tosho Gijutsu Hozon Kensankai and the Zen Nihon Togishi-kai conduct practical examinations to certify sword polishing techniques.

The following are general guidelines related to apprenticeship and practical work:

Among these, skilled togishi capable of finish polishing are even fewer in number. As the sword market becomes more active, demand for polishing services increases, but an absolute shortage of skilled togishi is becoming an industry-wide challenge.