fettle

In ceramic manufacturing, a fettle is the raised line or ridge that forms where two halves of a mould meet during the casting or pressing of clay. When slip is poured into a two-part mould, or when clay is pressed into interlocking mould sections, the liquid or plastic material flows into the narrow gap between the pieces. As it sets, the clay hardens around this parting line, creating a permanent seam that must be removed before firing.

The height and sharpness of a fettle depend on mould fit, pressure, and the fluidity of the clay body. A well-maintained mould with tight tolerances produces a fine, clean fettle; a worn or warped mould produces a thick, uneven one. On cast wares, the fettle often runs horizontally around the widest point of the form, such as the shoulder of a jug or the middle of a plate. Pressed ware may have multiple fettles from complex multi-part moulds.

Removal and waste

Fettles are removed by scraping, sponging, or turning with a blade or loop tool during the leather-hard stage, when the clay is firm enough to hold its shape but soft enough to cut cleanly. The scraped clay becomes waste unless it is recycled back into slop. This labour step adds cost and time; poorly removed fettles leave visible marks or weak points that fail during drying or firing. On high-end ware, especially tableware and decorative pieces, fettles must be completely invisible to the eye and undetectable by touch.

The term itself likely derives from the Old English word for a girdle or belt, reflecting the circular seam that often encircles a thrown or moulded vessel. In pottery dialects across Britain and Europe, the word remains standard; some potters also use spare or seam. Mould design and maintenance are critical to keeping fettles minimal, since every hour spent removing them is an hour not spent on decoration, finishing, or packing.