Iron Masters (Kanashi) and Sword Makers—The History of the Tatara Iron Smelters Who Supplied Tamahagane

Where Does Tamahagane Come From?—Tatara Iron Smelting and Iron Masters

Tamahagane, the material for Japanese swords, was produced through "tatara iron smelting," a traditional method of iron refining. The primary production centers for tatara iron smelting were in the Chugoku Mountains (an area spanning present-day Shimane, Tottori, Hiroshima, and Okayama prefectures), with the Okuizumo region of Shimane Prefecture in particular being known since ancient times as the "land of iron."

The expert group that conducted tatara iron smelting were called "iron masters (kanashi)." Iron masters were manager-technician groups who oversaw all processes involved in tatara iron smelting, from the extraction of iron sand (satetsu), management of the smelting furnace (tatara furnace), procurement of charcoal, to the distribution of products.

How Tatara Iron Smelting Works

The basic principle of tatara iron smelting involved alternately feeding iron sand and charcoal into a large clay furnace (approximately 1 to 1.5 meters tall and 3 to 4 meters long), using large bellows (balance bellows) to force air and conduct reduction smelting at high temperatures.

One operation (called "ichi-shiro") consisted of approximately 72 hours of continuous work and continued until the furnace became unusable. The iron mass extracted by destroying the furnace after operation was called "kera" (or "hana"), and when this kera was broken and sorted, it was classified into categories such as "tamahagane," "kera," and "cast iron (zuku)."

Of these, the portions with appropriate carbon content (approximately 0.6 to 1.5%) and good quality were selected as "tamahagane" for sword makers. Tamahagane obtained from one operation represented only about 10 to 15% of total production, with the remainder distributed as iron for agricultural tools and implements.

The Organization Structure of Iron Masters

The iron masters of the Chugoku Mountains established a highly organized management system during the Edo period. As typical organizations, major iron masters called "iron mountain masters (tetsuzanshi)" managed multiple small smelting furnaces (called "takadono") and employed numerous craftspeople and laborers.

Notable iron master families such as the Kondo family, the Sakurai family, and the Tanabe family wielded significant influence in the Shimane and Tottori regions. These iron masters were not merely iron smelters but wielded economic and political power as regional influencers and major landowners, sometimes establishing "a position of seller superiority over sword makers" through transactions with sword makers across various regions.

A division of labor system among craftspeople involved in iron smelting was also established, with the following being the main occupations.

Murage: The technical director of the entire smelting furnace. The chief technician overseeing control of heat, the amount of iron sand fed, and charcoal adjustment, holding the highest position among "tatara masters."

Daiku (carpenter): The construction technician responsible for building and repairing furnaces. Responsible for material selection of clay and stone as well as furnace structural design.

Sumikata (charcoal master): Responsible for charcoal procurement and management. Since securing quality charcoal directly affected the quality of iron smelting, the sumikata's technology and procurement network were an important source of competitive advantage.

Satetsu-hori (iron sand miners): The labor group responsible for extracting iron sand. Experiential skill in reading the distribution of iron sand in mountains was required.

The Relationship Between Iron Masters and Sword Makers—Complex Interdependence

The relationship between iron masters and sword makers was not a simple sales transaction where "iron masters sold tamahagane and sword makers bought it," but involved complex mutual dependence and tension.

Sword makers' ability to evaluate tamahagane: Sword makers evaluated the quality of tamahagane they purchased through methods such as "breaking it to examine the cross-section," "striking it to listen to the sound," and "observing the surface." The ability to discern high-quality tamahagane was one of the important skills of sword makers, and it is said that even when purchasing from the same iron master, the skill in selecting "good iron" differed from sword maker to sword maker.

Formation of regional brands: Regional brands such as "Izumo iron sand" and "Chugoku Mountains tamahagane" were formed through sword makers' trust and evaluation. Many sword makers had preferences for specific iron masters' tamahagane, calling it "the iron of master ○○," and long-term trading relationships were formed.

Negotiation over supply volume and quality: Since iron masters supplied tamahagane to multiple sword makers, they held the power to choose "which sword makers should receive priority in high-quality tamahagane supply." While renowned sword makers could secure high-quality tamahagane at high prices, newly arrived sword makers sometimes had to make do with leftovers.

Exchange of technical information: There was a bidirectional flow of technical information between iron masters and sword makers. Feedback from sword makers ("recent tamahagane has less carbon," "iron from this part is difficult to develop hamon," etc.) was used by iron masters to improve manufacturing, while technical information from iron masters ("this year's iron sand quality is better than usual," "we tried a new furnace construction method," etc.) influenced sword makers' material selection.

Tamahagane Distribution and Prices in the Edo Period

During the Edo period, tamahagane distribution was conducted primarily through sword and blade wholesalers in Edo, Osaka, and Kyoto. A multi-stage distribution channel was formed where regional iron masters sold to regional wholesalers, regional wholesalers sent goods to receiving wholesalers in Edo and Osaka, and receiving wholesalers sold to sword makers and sword dealers.

The price of tamahagane varied greatly depending on the period, region, and quality, but it is said that in the mid-Edo period, the cost of obtaining the tamahagane (approximately 8-12 kg) needed for a sword maker to produce one tachi matched the monthly wage of a skilled craftsman. Securing high-quality tamahagane was a serious business challenge for sword makers.

Modern Tatara Iron Smelting—The NBTHK Tatara and Securing Tamahagane

After the Meiji period, traditional tatara iron smelting rapidly declined due to the spread of Western-style iron smelting technology. Tatara iron smelting, which had nearly disappeared by the Taisho period, was revived by the "NBTHK tatara" which began operations in Okuizumo, Shimane Prefecture, starting in 1977 (Showa 52).

The NBTHK tatara, led by the Japanese Sword and Art Preservation Society (NBTHK), produces the tamahagane needed by modern sword makers through one annual operation (in winter). Currently, nearly all tamahagane used by sword makers recognized by Japan's Agency for Cultural Affairs is produced by this NBTHK tatara, achieving stable supply to sword makers.

However, the amount of tamahagane that can be produced by the NBTHK tatara is limited, and it is said to constantly be on the verge of not meeting the demand of sword makers across the country. Furthermore, there is discussion comparing the quality uniformity of tamahagane to traditional Edo-period tamahagane, and among researchers, "differences between modern and ancient tamahagane" is an ongoing research topic.

Conclusion—Iron Masters: Unsung Supporters of Sword Maker Culture

The beauty and function of Japanese swords are often attributed to the technology of sword makers. However, without the iron masters who produced the material that supported sword makers' technology—tamahagane—and without tatara iron smelting as their technological system, the heights of Japanese sword culture would not have been achieved. Iron masters, as bearers of the "material and economic foundation that supported sword makers as artists," are an indispensable presence in the history of Japanese swords. The contemporary continuation of tatara iron smelting and the research and preservation activities that support it are important efforts for passing on Japanese sword culture in its entirety to the next generation.