Underglaze decoration involves applying color to ceramic ware in its raw, porous state before the initial firing (bisque firing). This technique utilizes various colorants, including oxides, carbonates, and prepared stains, mixed with a medium to facilitate application. For example, a cobalt-based mixture can be brushed onto unfired pottery to achieve a rich blue hue after glazing and firing.
This method allows deep color saturation and integration with the clay body. Because the unfired clay is absorbent, the color becomes an integral part of the piece, resulting in vibrant and durable decoration. Historically, underglaze techniques have been employed in diverse ceramic traditions worldwide, contributing to the aesthetic richness of pottery from ancient times to the present day. This fundamental approach allows for a wide range of decorative possibilities, from simple lines and washes to intricate designs.
