Sometsuke (Blue-and-White Underglaze)

Sometsuke (染付) is the technique of painting a design in cobalt oxide pigment directly onto unfired, unglazed porcelain, then covering it with a clear glaze before a single high-temperature firing. The cobalt turns a deep blue during firing and sits sealed beneath the glassy surface, which is why sometsuke pieces keep their crisp blue-on-white look indefinitely and are dishwasher- and microwave-safe in a way that overglaze enamel decoration is not. Japan adapted the technique from Chinese blue-and-white porcelain in the early 17th century, and it became the founding style of Arita ware, Japan’s first porcelain tradition.