Square tea ceremony kettle.

Clay mold casting

In clay mold casting (sōgata), a symmetrical mold is produced by rotating a template called a strickle board in a mixture of sand and clay to shape the walls of the mold. Clay mold casting is predominantly used to produce tea ceremony kettles and temple bells. After the piece is removed from the mold, it is heated and painted with lacquer (urushi) or a solution of iron, vinegar, and alcohol known as ohaguro (“teeth blackening liquid”) to produce a unique, dark finish.