When researching traditional Japanese bladesmithing practices, you may come across the term "tatara." Based on the name alone, it's difficult to surmise what exactly a tatara is, let alone how it's used to create swords like the katana and wakizashi. Nonetheless, tataras played an important role in traditional Japanese bladesmithing by providing the furnace in which metals and additives were smelted. To better understand tataras and how they were used to create some of the world's highest quality swords, keep reading.
Overview of Tataras
Originating in Japan, a tatara is a large furnace used to smelt iron, coal and other materials for use in bladesmithing. It's unknown who invented the tatara or when they did it, though some historians believe that it may have occurred when the Japanese kingdom met with its neighbours in Korea. During these common meetings, the two kingdoms would share their ideas and technologies, including those pertaining to bladesmithing. Therefore, it's plausible that Japan borrowed at least some of the ideas for a tatara from Korea.
How It Was Used
The tatara featured a large clay vessel -- about 4 feet tall, 12 feet long and 4 feet wide -- in which iron-rich river sand was fired and smelt down. Although there were several variations available, most had a tub-like design. After the tatara had dried, it placed over a fire to harden it. This was a critical step, as the smelter had to wait for the fire to reach a specific temperature before adding other compounds to the smelted solution. This was a tedious process that often took several days to complete as well as four or five people.
Towards the end of the smelting process, a smelter would break the tatara and remove the steel bloom. Reports suggest that a typical traditional Japanese tatara used up to 10 tons of iron-rich river sand and 12 tons of charcoal. The end result of this process was about 2.5 tons of high-carbon tamahagane steel, which could be used to create katanas, wakizashis and other traditional Japanese bladed weapons.
The Nittoho Tatara
Some people assume that tataras were only used in the past to create high-quality traditional Japanese swords, but this isn't necessarily true. In the mid- to late 1970s, the Japanese Society for Preservation of Japanese Art Swords, along with the Agency for Cultural Affairs and Hitachi Works, constructed a special tatara known as the Nittoho Tatara. Featuring a meticulously crafted design, it's designed to produce the steel needed to create modern Japanese swords. According to Wikipedia, the Nittoho Tatara is only active during the winter. When winter arrives, the aforementioned organizations fire up to this historical tatara to produce the high-carbon steel used to create modern Japanese swords.