Hadori and Nugui: The Master Polisher's Final Techniques for Bringing Out a Blade's Hamon

The Overall Picture of Polishing and the Positioning of "Finishing Polish"

Japanese sword polishing (togi) is not merely "work to sharpen a blade," but an aesthetic and technical act of bringing out the sword's true appearance. The polishing master (togishi), by progressively using finer whetstones to remove scratches, performs a finishing that displays the jigane grain pattern and hamon to their maximum beauty.

The polishing process is broadly divided into three stages: "rough polishing (aratogi)," "medium polishing (nakatogi)," and "finishing polish (shiagetogi)."

• Rough polishing (aratogi): Correcting the form and removing large scratches
• Medium polishing (nakatogi): Uniforming the surface
• Finishing polish (shiagetogi): Making the jigane shine and maximizing the contrast of the hamon

The techniques of "hadori" and "nugui" play central roles in this finishing stage.

The Technique of Hadori

Hadori is a technique used in the final stage of finishing polish, in which thin fragments of a special whetstone called uchigumorido (also called yubi-togishi) are attached to the finger, and the blade region from the kissaki to the hamon is finely polished.

Uchigumorido is a natural whetstone mined from quarries in Kyoto (areas such as Kameoka City and Kyohoku District), characterized by extremely fine particles and the effect of polishing while creating a white haze on metal surfaces. This "white haze" becomes the visual foundation for the hamon to stand out. The "nie" (grainy white luster) and "nioi" (misty, soft light) of the hamon emerge visually for the first time through the angle and pressure of the whetstone application during the hadori stage.

Hadori is applied with extremely delicate pressure along the hamon line, from the hamatchi toward the kissaki. Applying too much force causes the hamon to "disappear," while insufficient pressure blurs the boundary with the jigane. Experienced polishing masters adjust the pressure distribution of their fingers according to each swordsmith's style, the era, and the characteristics of the jigane, based on decades of experience. Particularly in works like koto with complex jigane, every stroke of hadori reflects decades of experience.

The Role of Nugui

Nugui is, alongside hadori, an element of finishing polish that prepares the "ji" section apart from the hamon band—the shinogiji and hiraji. By thinly coating nugui paper (special washi paper) with whetstone powder or sword oil, and repeatedly wiping the sword blade's jigane section in one direction, the grain pattern of the jigane (itame, masame, mokume, etc.) emerges, revealing a pattern called "chikei."

Through nugui, a unique white luster emerges on the jigane (related to utsurim), creating a strong contrast with the hamon. The more complex the hamon—such as the "choji-midare" of Bizen tradition or the "hitatsura" of Shoshu tradition—the more greatly does the nugui technique influence the quality of the finish. Nugui and hadori are complementary techniques; neither alone achieves the highest quality finish.

The Selection and Scarcity of Whetstones

One of the serious problems facing modern polishing masters is the dramatic decline in production of natural whetstones, including uchigumorido. In the northern Kyoto region, where high-quality uchigumorido is mined, extraction volumes have been declining year by year, and sourcing good stones depends heavily on connections among polishing masters and auctions (whetstone markets).

While artificial whetstones are being developed as substitutes for natural whetstones, the "depth" and "soft finish" created by the non-uniform particle size (subtle variation) unique to natural whetstones are said to be difficult to replicate with artificial stones. Premium uchigumorido used in the highest levels of art polishing can exceed several hundred thousand yen, becoming an economic challenge for polishing masters. Some polishing masters inherit old whetstones across generations, and the whetstones themselves are sometimes treated as intangible assets.

The Difference Between Art Polishing and Practical Polishing

Polishing is divided into two types: "art polishing (bijutsutogi)" and "practical polishing (jitsuyoutogi)."

• Art polishing (bijutsutogi): The highest standard of finish in preparation for authentication and examination by organizations such as the NBTHK, with hadori and nugui repeated many times to maximize the beauty of the jigane and the expression of the hamon. The work period can take from several weeks to over a month per sword.
• Practical polishing (jitsuyoutogi): Polishing for swords used in iaido or sword training, prioritizing sharpness and durability over the level of time invested in art polishing. However, a certain level of polishing skill is still necessary, and because having an attributed masterwork with a certificate undergo practical polishing could reduce its artistic value, this practice is typically avoided.

The Training of Polishing Masters and the Transmission of Technique

The techniques of hadori and nugui are a typical example of craftsmanship learned "by watching," and there are no systematized texts or manuals. It is said that only after over ten years of training under a master can one become independent, and in the modern era, the number of polishing masters is limited. The handful of experts in full-fledged art polishing throughout the nation—reportedly only several dozen—are indispensable to the preservation of Japanese sword culture.

The training of polishing masters, like that of swordsmiths, is a subject of support by the government and the Agency for Cultural Affairs, and is linked with the certification system for traditional craftspeople. The shortage of successors is also a serious issue in the world of polishing masters, and when one excellent polishing master ceases work, it directly impacts that region's Japanese sword culture. The existence of polishing masters who can perform hadori and nugui at a high level is human capital that should be supported by the industry as a whole, to preserve the value of swords in collectors' holdings.