Today, Sam Hoffman shows us his method for trimming plates with altered rims on the pottery wheel.
Altering the circular form of a plate is an exciting means of expression for ceramic artists, but it can also present difficulties at the trimming stage. If the rim of a plate is cut or manipulated into an asymmetrical shape, or is delicate, the piece cannot simply be inverted onto another bat for trimming. Instead, the piece must be placed on a clay chuck that supports the plate in the center.
To create this chuck, form a large coil from the same clay body that the plate was made from. Attach the coil to the wheel head in the shape of a donut, making sure that enough height is established to hold the plate above the wheel head. Flatten and smooth the coil using as little water as possible, creating a rounded cushion on which to rest the plate. It is important to let the plate stiffen up a little bit more than usual before trimming to avoid flexing or chipping the altered lip when the piece is inverted.
Leaving the plate on the bat it was thrown on, carefully flip the plate onto the palm of one hand or a small bat the fits the center of the plate. Place the upside-down plate onto the coil and make sure that it is centered. Gently press down on the middle of the plate to create a vacuum that will hold the piece in place.
Start trimming by removing excess clay from the outside of the plate. Trim the plate using the same techniques as usual, taking care to avoid the delicate lip that hangs over the wheel head. When the foot rings are trimmed, smooth the bottom of the plate and carefully remove it from the coil. If the inside surface of the plate has been marred from resting on the coil, use a sponge to clean it up.