From clay to kiln

A porcelain object starts with its body: the prepared material that will become the shape we hold or display. In the Chinese hard-paste tradition, kaolin and porcelain stone are important ingredients. Their preparation and firing contribute to porcelain’s characteristic hardness and, in thin sections, translucency. Those qualities depend on the material and how it is worked; the word porcelain does not tell us every detail of an object’s production.

Shape, glaze and decoration are distinct parts of the process. Underglaze decoration sits beneath the glaze layer. Familiar blue-and-white porcelain uses cobalt pigment to create its blue designs. Overglaze decoration is applied above the glaze. These terms describe where color sits, and they help explain why two painted surfaces can look different.

The sequence varies with the technique. A film of traditional production at Jingdezhen, held by the Smithsonian, follows specialists preparing bodies, forming vessels, glazing, decorating and firing. It offers a view into one documented practice rather than a fixed recipe for every porcelain piece.

Firing changes clay permanently. It is also a stage at which an object can warp, crack or fuse to something beside it. Historic protective cases called saggars helped shield ceramics from direct flame and kiln debris, although they could fail too.

Look again at a finished piece with these stages in mind. Its silhouette, painted marks and glazed surface can be considered separately, then together. That makes looking more precise, even before the production details of the individual object are known.