meetings with sword makers and polishers. I am very honored to have been welcomed into the workshops and homes of many top craftsmen. Two, in particular, have contributed much of their time, resources, and knowledge to this project. The first craftsman is Kawachi Kunihira, a 15th generation sword maker in the mountains of Nara prefecture. The second craftsman, Abe Kazunori, is a sword polisher in Tōkyō. This chapter outlines the processes involved in creating a Japanese sword through their daily practices. In essence, they will act as our tour guides as we explore the creation of Japanese swords.
Carefully watching the fire and steel, the master smith and his apprentices await the perfect moment to work the glowing billet.
Both Mr. Kawachi and Mr. Abe have been declared mūkansa, or master craftsmen, a title awarded to artisans having received more than the prescribed number of Special Prizes at the yearly NBTHK competitions. Each has studied under the most famous teachers in Japan and holds a number of private and governmental honors. Yet, despite their highly specialized skill sets, each of these men would politely reject any compliment. They would assert that working with swords is just what they do. They are not holy-men, shamans, or priests, just hardworking craftsmen. Regardless of their humility, it is easy to appreciate their passion, exacting standards, and dedication to maintaining traditional arts.
Central to the Japanese swordsmiths’ craft is the ability to create a sword from a difficult raw material, combining various densities of steel into an ingenuous sword-structure. The resulting sword has durable outer layers combined with a soft core that is not easily broken. Known for their razor-sharp edge, elegant curve, and graceful steel patterns, the appreciation of nihōntō extends far beyond mere metallurgy or warfare. Yet it is the metallurgy and combat applications that make the Japanese sword so alluring.
Manufacture of Traditionally Smelted Steel
Historically, two processes have been used in the traditional manufacture of Japanese iron and steel. These two processes are referred to as zūkū-ōshi and kera-ōshi. The former closely resembles the “pig iron” (a type of cast-iron) produced in high-temperature furnaces, while the later is a type of low-fired sponge iron. The difference between them is that in the kera-ōshi process, the iron doesn’t liquefy, but rather agglutinates into one mass. When it comes out, it looks spongy—thus, the name “sponge iron.” Surprisingly, in Japan, it is thought that high-temperature zūkū-ōshi was the main technology of the Middle Ages, whereas kera-ōshi became dominant in later times, and remains popular today. This seems contrary to the chronological evolution of metallurgy in the West.
Today, the sword-steel tamahagane, one of the products of a kera-ōshi tatara, is jointly produced almost exclusively by a partnership involving Hitachi Metals, the Japanese government, and the NBTHK in Yokota, a small town in Shimane prefecture. In this process, iron ore contained within dark brown or black sand is smelted in a clay furnace, using charcoal as the fuel as well as reducing agent. The liberated iron then combines with more carbon to form steel alloys. Some swordsmiths operate their own tatara within the confines of their smithies and produce their own tamahagane. Producing tamahagane on such a small scale, however, is quite difficult and rare. Today, traditionally produced NBTHK tamahagane is chosen by many smiths; despite its high cost. It is important to note that some smiths use steel produced in ways other than from the NBTHK tatara.
Master sword polisher Abe Kazunori assesses a blade with careful consideration.
Broken chips of tamahagane can be stacked and forge-welded into a billet.
A painting showing a selection of tools used in the tatara for the creation of swords.
Iron-bearing sand is refined into sponge-iron, pieces of which can be stacked to form a billet.
Working with a steady, syncopated rhythm, the apprentices elongate and fold the steel during tanren.
Mr. Kawachi and his apprentices have just completed a fold and quickly work to weld the surfaces together.
These are pieces of re-smelted iron and steel for use in creating an oroshi-gane billet.
Once the billet has been forge-welded together it is folded repeatedly, creating layers within the steel.
Tamahagane is not the only type of raw material used in sword making. For example, ōrōshigane is a process that consists of re-smelting, in the smith’s own forge, various bits of iron, steel or cast iron in order to make them usable in sword making. Broken cast iron kettles, ancient temple hardware or farming tools are all acceptable sources for ōrōshigane. The process, depending on how it is performed, will increase or decrease the carbon content of the metal, and form it into a single lump. The end product is also referred to as ōrōshigane, as opposed to tamahagane.
Both the tamahagane and ōrōshigane aim to manipulate a symphony of delicate factors. Carefully controlling the carbon content, homogeneity, crystallinity, and other factors allows the raw steel to achieve the quality needed for sword steel. Some pieces of steel are unusable because of their excessively high or low carbon content, poor structure, and so on, and must be put aside. The smith may decide to re-smelt these odds and ends for a later project in ōrōshigane.
It must be understood that, except in rare cases, specialized craftsmen work alongside a few swordsmiths to manufacture sword steel at the NBTHK tatara. Together, they prepare the tamahagane for sword-making by smiths around Japan. Without the efforts and skills of the craftsmen at this early stage, there would be few nihōntō for us to appreciate today.
Refining the Steel By Forge-Folding (Tanren)
The term tanren, describes both the processes involved in preparing the raw tamahagane and making it ready for swordmaking. When tamahagane reaches Mr. Kawachi it is not ready to be made into a sword. Nor does the tamahagane resemble steel, as most readers would envision it. The raw material looks like a shiny and spongy rock. The processes involved in tanren are some of the most unique and important skills mastered only by traditional Japanese sword makers today (the other being quench-hardening). There are different ways to perform tanren; many considered trade secrets.
The steel is refined and strengthened while undergoing the forge-folding process.
There are several ways that a smith might begin to prepare the raw material. For example, in a process called mizū-beshi, the raw tamahagane is hammered out into thin wafers. The wafers are then quenched, making them very brittle. The smith crunches the brittle steel into smaller flat chunks about 4 cm wide. The fracturing allows them to be sorted into groups of varying carbon content and overall quality.
After the raw steel is
