Tatara

A tatara is a traditional Japanese furnace for smelting iron and steel directly from ironsand, and the term also names the low clay-walled building built to house it. The technique originated in Kibi Province around the middle of the sixth century AD and spread across Japan, with western regions favoring a low box-shaped furnace and eastern regions using both the box design and a vertical form found nowhere else. A single smelting run in a tatara lasts roughly three days out of a week-long operation, alternately layering about 9.1 tonnes of ironsand with 11 tonnes of charcoal inside a clay vessel roughly 1.1 meters tall, 3 meters long and 1.1 meters wide, to yield about 2.3 tonnes of the refined steel called tamahagane. The late seventeenth century brought the foot-operated tembin bellows, which raised furnace temperatures and improved the steel, but Western blast furnaces made tatara smelting commercially obsolete by 1920; the Nittoho society revived a working tatara in Shimane Prefecture in 1977, which still operates seasonally to supply steel for traditional Japanese sword making.