This chawan was fired at the Kakuzan-gama, a kiln built in 1959 inside the Kyoto headquarters of Ōmoto, a Japanese religious movement, by Kaneshige Sozan, a member of Bizen's most celebrated pottery family. It is signed by Deguchi Eiji, who served as Ōmoto's Sōchō (director) from 1958 to 1962. A single white glaze on this bowl developed rust, near-black and crystalline blue effects during firing, the result of flame position, ash deposit and heat variation inside a wood kiln, not of painting or decoration.

Bizen-yaki is never glazed and never painted. Everything visible on a finished piece was decided during the firing itself, by potters who spend two weeks feeding a kiln by hand, reading the fire instead of a dial. On a return visit to Shibaoka Tōsendō, the Kōzan-gama kiln in Imbe, here is what that actually looks like from the inside.