Throwing a flat sitting lid is a fundamental skill that separates functional pottery from true craftsmanship. This technique involves creating a disc of clay that lies perfectly flat on the table without warping, twisting, or developing cracks at the center. Mastering this process is essential for anyone who wants to create stable bases for bowls, plates, or serving trays, as it provides the reliable foundation upon which all subsequent building depends.
Understanding the Physics of Clay
The success of a flat sitting lid begins long before the wheel is even turned. It requires a deep respect for the mechanics of moist clay. As the potter’s hands apply pressure, the clay must compress evenly to eliminate air pockets and achieve consistent density. If the center is compressed more than the outer edge, the disc will warp into a bowl shape. Conversely, if the rim is pressed down too forcefully, the center will bulge upward. The goal is to coax the clay into a state of uniform thickness and tension, where the molecular structure is stable and relaxed.
Preparing the Perfect Centered Mass
Before opening the clay to form a disc, achieving a solid center is non-negotiable. A wobbly or off-center mass will guarantee a warped lid, regardless of how carefully the rim is handled. The potter must ensure the clay is firmly anchored to the bat, with no risk of shifting. The walls of the centered column should be straight and smooth, tapering slightly inward toward the top. This stable core acts as the axle upon which the flat disc will rotate, ensuring that force applied to the top is distributed radially rather than eccentrically.
The Technique of Opening and Levelling
With the centered mass secured, the moment of truth arrives: the opening. Using the pads of the fingers, the potter applies gentle but firm pressure downward at the exact center, parting the clay to create a small aperture. The key is to move slowly, feeling the resistance of the material. Simultaneously, the outer edge must be coaxed outward with the other hand, maintaining the diameter required for the final lid size. The critical step comes after the hole is established; the potter must scrape the very bottom of the disc with a rib tool, lifting slightly at the edges to ensure the entire surface settles to the same level plane.
Refining the Rim and Final Flatness
Once the clay is open and generally flat, attention turns to the rim. The edge often becomes slightly thicker or uneven during the opening process, causing the lid to "sit" incorrectly. This is corrected by gently rolling the rim between the fingers or using a rubber rib to compress the circumference uniformly. To test the flatness, many experienced potters place the lid directly onto a known flat surface, such as a plaster bat or a rigid tabletop. If the lid rocks even slightly, the high spots must be carefully trimmed or sanded down until the rocking motion ceases entirely.
Drying and the Risk of Warpage
Even a perfectly thrown flat sitting lid can be ruined during the drying phase. Clay shrinks as it loses moisture, and this contraction creates tension across the surface. If the rim dries faster than the center—or if the lid is exposed to a direct draft—it will curl upward, transforming a flat shape into a concave saucer. To prevent this, the lid should be dried slowly and evenly, often under plastic sheeting that allows it to breathe without drying too quickly. Some potters dry the lid while it is still attached to the bat, cutting it free only when the clay has reached a leather-hard state that resists deformation.
Trimming for Perfection
For advanced practitioners, the journey to the perfect flat lid often concludes at the trimming table. Once the clay is leather-hard, the lid is removed from the bat and secured to a spinning bat of its own. A sharp loop tool or ribbon tool is then guided along the bottom edge and the center. This process removes the excess clay that accumulates during throwing, creating a sharp, clean angle where the lid meets the table. Trimming not only enhances the aesthetic of the flat sitting lid but also removes weight, making the final piece feel lighter and more elegant in the hand.
