Sobokai also read as Ubagafutokoro. To this day, there are various theories, and a clear kiln location has not been identified.
It is said to have been started by Kato Kagemasa, the potter from Seto. The signature of Ubagafutokoro was found on Ofuke ware from around the Genna period (1615–1624), while symbols from this kiln are also found in works fired at Toyama in the Owari Domain. We anticipate further research to identify the kiln.
Sobokai clay
There is a legend that “the potter Toshiro (Kato Shirozaemon) found suitable clay for pottery in Seto, Sobokai, and settled in Seto to make pottery from that clay. The clay is a type of clay called Kibushi-nendo, which is characterized by its fine texture, high viscosity, and ability to keep its shape. This clay, which contains a lot of iron and turns reddish-black when fired, is thought to have been especially suitable for the production of tea utensils because it enables thin construction and complex deformation by the potter’s wheel, and it is also strong when fired.
It is known that the Owari clan had a monopoly on Sobokai clay by bringing it into the castle’s storehouse. At one time, pottery tea utensils were so expensive, Samurai said that a castle could be built with a single tea utensil. Later, it became less expensive and there were many Seto-ware tea utensils made of Sobokai clay.
