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 the kanarishi

Tamahagane, the material used in Japanese swords, is produced through "tatara iron smelting," a traditional method of iron refining. The main production area for tatara iron smelting was the Chugoku mountain range (a region spanning present-day Shimane, Tottori, Hiroshima, and Okayama prefectures), and in particular, the Okuizumo region of Shimane Prefecture has long been known as the "iron country." The specialists who conducted tatara iron smelting were known as "kanarishi" (iron masters). The kanarishi were entrepreneur-technicians who oversaw all aspects of tatara iron smelting, from the extraction of iron sand (satetsu), the management of smelting furnaces (tatara furnaces), the procurement of charcoal, to the distribution of products. When discussing the beauty of Japanese swords, attention tends to focus on the skill of the sword smith, but it is essential to know about these workers who toiled behind the scenes.

How tatara iron smelting worked

The basic principle of tatara iron smelting involved alternately loading iron sand and charcoal into a large clay furnace (approximately 1 to 1.5 meters in height and 3 to 4 meters in length), then using a large bellows (a balance bellows, or tebin-fuigo) to force air through it while performing high-temperature reduction smelting.

A single smelting operation (called "ひとしろ" or "one generation") consisted of approximately 72 hours of continuous work and continued until the furnace became unusable. After the operation, the iron lump taken from the destroyed furnace was called "kera" or "hana" (flower). When this kera was broken apart and sorted, it was classified into categories such as "tamahagane," "kera," and "sentetsu" (zinc).

Of these, the portion with appropriate carbon content (approximately 0.6–1.5%) and good quality was selected as "tamahagane" for sword smiths. The amount of tamahagane obtained from a single smelting operation was approximately 10–15% of total production, with the remainder distributed as iron for agricultural tools and implements. The scarcity of high-quality tamahagane fundamentally supported the rare value of Japanese swords themselves.

The organizational structure of the kanarishi

By the Edo period, the kanarishi of the Chugoku mountain range had established a highly organized management system. As a representative organizational form, large kanarishi called "tetsu-zanshi" (iron mountain masters) managed multiple small-scale smelting furnaces (called "takadono") and employed many craftsmen and laborers.

Representative kanarishi families such as the Tanabe family, the Sakurai family, and the Itohara family wielded significant influence in the Shimane and Tottori regions. These kanarishi were not mere iron producers; as regional leaders and major landholders, they possessed economic and political power, and through dealings with sword smiths throughout the region, they sometimes established "a position of advantage as sellers over sword smiths."

A division of labor among craftspeople involved in iron smelting was also established, with the following being major occupational categories:

• Murage (village head): The technical director responsible for the entire smelting furnace. The highest-ranking technician who oversaw fire control, the volume of iron sand input, and charcoal adjustment, and held the highest position among "tatara masters."
• Daiku (carpenter): A building technician responsible for furnace construction and repair. This person undertook the selection of materials such as clay and stone, and the structural design of the furnace.
• Sumikata (charcoal person): Responsible for the procurement and management of charcoal. Since securing high-quality charcoal was directly connected to the quality of smelted iron, the technical expertise and procurement network of the charcoal person were a key source of competitive advantage.
• Satetsu-hori (iron sand digger): A group of workers engaged in the extraction of iron sand. This work required experiential skill in reading the iron sand distribution in mountains.

The relationship between kanarishi and sword smiths——complex interdependence

The relationship between kanarishi and sword smiths was not a simple buying-and-selling transaction in which "the kanarishi sold tamahagane and the sword smith bought it," but rather involved complex interdependence and tension.

• Sword smiths' ability to evaluate tamahagane: Sword smiths evaluated the quality of tamahagane they purchased by "breaking it and examining the cross-section," "striking it and listening to the sound," and "observing the surface." The keen eye to discern high-quality tamahagane was one of the important techniques of the sword smith, and it is said that even when purchasing from the same kanarishi, different sword smiths differed in their skill at selecting "good iron."
• Formation of regional brands: Regional brands such as "Izumo iron sand" and "Chugoku mountain range tamahagane" were formed through the trust and evaluation of sword smiths. Many sword smiths preferred the tamahagane of particular kanarishi, calling it "the iron of ○○ master," and long-term trading relationships were established.
• Negotiations over delivery volumes and quality: Since kanarishi supplied tamahagane to multiple sword smiths, they possessed the choice of "which sword smith should receive priority in high-quality tamahagane supplies." Famous sword smiths were able to secure high-quality tamahagane at higher prices, while novice sword smiths sometimes had to make do with what remained.
• Exchange of technical information: There was a two-way flow of technical information between kanarishi and sword smiths. Feedback from sword smiths (such as "recently the tamahagane has had less carbon," or "the iron from this part does not show hamon easily") was utilized in the kanarishi's production improvements, while technical information from the kanarishi side (such as "this year the iron sand quality is better than usual," or "we tried a new method of furnace construction") influenced sword smiths' material selection.

Tamahagane distribution and pricing in the Edo period

During the Edo period, tamahagane distribution took place mainly through sword and blade wholesalers in Edo, Osaka, and Kyoto. A multi-stage distribution route was formed: regional iron masters sold to regional wholesalers, regional wholesalers sent to receiving wholesalers in Edo and Osaka, and receiving wholesalers sold to sword smiths and blade merchants.

The price of tamahagane fluctuated greatly depending on the era, region, and quality, but in the mid-Edo period, the cost for a sword smith to obtain the tamahagane needed to make one tachi (approximately 8–12 kilograms) was said to be equivalent to the monthly wage of a skilled craftsman. Securing high-quality tamahagane was a major management concern for sword smiths, and the most talented sword smiths put effort into discerning materials.

Modern tatara iron smelting——NBTHK tatara and securing tamahagane

After the Meiji period, traditional tatara iron smelting rapidly declined as Western iron smelting techniques became widespread. The "NBTHK tatara," which began operations in the Okuizumo region of Shimane Prefecture in 1977 (Showa 52), revived tatara iron smelting, which had become nearly extinct by the Taisho period.

The NBTHK tatara, led by the Japanese Sword and Art Sword Preservation Society (NBTHK), produces the tamahagane needed by modern sword smiths through one annual operation (in winter). Currently, nearly all tamahagane used by culturally designated sword smiths in Japan is produced by NBTHK tatara, ensuring a stable supply to sword smiths.

However, the amount of tamahagane that NBTHK tatara can produce is limited, and it is said to be constantly on the edge of meeting the demand of sword smiths throughout the country. Additionally, regarding the quality consistency of tamahagane, there is discussion when compared with traditional Edo period regional tamahagane, and "the difference between modern tamahagane and old tamahagane" continues to be a research topic among scholars. Since works created by modern sword smiths can also be viewed in TOUKENZA's online catalog, please try to feel the individuality created by material differences from the blade itself.

Conclusion——the kanarishi were unsung supporters of sword smith culture

The beauty and function of Japanese swords are often attributed to the technique of the sword smith. However, without the kanarishi who produced the material supporting the sword smith's technique——tamahagane——and the technical system of tatara iron smelting, the heights of Japanese sword culture would never have been achieved. As bearers of "the material and economic foundation supporting the artist known as the sword smith," the kanarishi were an indispensable presence in the history of Japanese swords. The contemporary inheritance of tatara iron smelting and the research and preservation activities that support it are important undertakings for passing on the entirety of Japanese sword culture to the next generation.