Andy Foster's work is inspired by slip-decorated stoneware created in New York that dates back to the 1800s. He likes to like to think that his work "memorializes our forebears, whose ingenuity and craftsmanship laid the foundations for anyone who chooses to work with clay."
In this post, an excerpt from the 2026 issue of Studio Talk, Andy walks through his full process for making large slip-decorated platters, starting with making a plaster hump mold, to adding a thrown foot to the hump-molded slab, to finishing the surface with a wax-resist slip application. - Jennifer Poellot Harnetty, editor
The first step is to create a plaster slump mold. I use the smoothest possible clay for this part of the process, as it requires less refinement of the final plaster form, although any throwable clay will do. Begin by laying a clay slab onto a bat on your wheel and attaching a 1-inch (2.5-cm)-thick coil around the edge of the slab (1). How thick the base slab is and where you attach the coil determines how deep and wide the final object can be. For example, if a wide, flat platter is desired, you could start with a 1-inch (2.5-cm)-thick slab and attach the coil 8 inches (20.3 cm) from the center, which will produce a 16-inch (40.6-cm)-diameter platter (before shrinkage).
Pull the coil up so that the interior height is about 1 inches (3.8 cm) (2), keeping in mind that you will be pouring plaster into this form and the wall will need to hold for the entire time it takes the plaster to cure. Refine the interior shape with a metal rib and use a large loop trimming tool to define the lip and the well of the plate (3). What you see now will be what the final plate form looks like, so it is important to make everything as refined as possible.
While the clay is still wet, take the bat to a level table. Make a rough estimate of how much plaster you will need by treating the clay mold like a cylinder and finding its approximate volume. You can find a chart online for the appropriate water-to-plaster ratio for whatever plaster you are using. Mix plaster and water, using warm water and a high-speed drill to speed up the curing time. When the plaster starts to thicken, pour it into the mold and leave it to cure for about an hour (4). Once the plaster has cured, tear it out of the clay form. Clean up any sharp edges with a rasp (5). I leave the mold to dry in front of a fan or near a hot kiln until it no longer feels cool to the touch, which may take a couple of days to a week, depending on humidity.
Using the Mold, Forming Your Platter
When the mold is fully dry, center it on the potters wheel, preferably with a piece of foam underneath to prevent it from sliding around. Roll out a slab that is slightly thicker than you want the final piece to be, and compress one side until it is smooth. Drape the slab, smooth side down, onto the mold and compress the slab onto the mold while the wheel spins, moving from the center out to the rim to prevent any air pockets from forming (6).
Use a needle tool to cut the excess clay around the edge (7). Roll out a long coil and attach it at the point where the well of the plate meets the flange, making sure to slip and score (8). Throw the foot until it is the desired depth, then use a rib to round off the bottom of the foot (9). You may have to use a needle tool to level the foot if it becomes too uneven after the initial throwing. Once you are happy with how the foot looks, drape the form with plastic and leave it to firm up.
Once the platter is firm enough to mold its shape, place a bat on the foot and flip the platter in one smooth motion. The plaster mold should lift free, but may need coaxing with some compressed air.
Return the platter to the wheel and use your trimming tools and ribs to round the rim, making sure not to deform it (10). Leave the platter loosely draped in plastic until it is the consistency of a sharp cheddar cheese. Apply wax in quick, confident strokes with a brush, making sure to consider the layout of your design as you go (11). It may be helpful to draw the design with a soft pencil first, but bear in mind that if the clay is too soft you may leave unwanted marks. Consider waxing the foot as well; it will make cleanup after the slip application easier. Leave the wax to cure for up to one day, depending on the brand, making sure to keep the platter covered. Apply your slip by either dipping (12) or pouring. Do not attempt to clean up the waxed areas until the slip has dried enough to touch; then, gently clean with a damp sponge or paper towel.
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Published Jan 3, 2012
The first step is to create a plaster slump mold. I use the smoothest possible clay for this part of the process, as it requires less refinement of the final plaster form, although any throwable clay will do. Begin by laying a clay slab onto a bat on your wheel and attaching a 1-inch (2.5-cm)-thick coil around the edge of the slab (1). How thick the base slab is and where you attach the coil determines how deep and wide the final object can be. For example, if a wide, flat platter is desired, you could start with a 1-inch (2.5-cm)-thick slab and attach the coil 8 inches (20.3 cm) from the center, which will produce a 16-inch (40.6-cm)-diameter platter (before shrinkage).
While the clay is still wet, take the bat to a level table. Make a rough estimate of how much plaster you will need by treating the clay mold like a cylinder and finding its approximate volume. You can find a chart online for the appropriate water-to-plaster ratio for whatever plaster you are using. Mix plaster and water, using warm water and a high-speed drill to speed up the curing time. When the plaster starts to thicken, pour it into the mold and leave it to cure for about an hour (4). Once the plaster has cured, tear it out of the clay form. Clean up any sharp edges with a rasp (5). I leave the mold to dry in front of a fan or near a hot kiln until it no longer feels cool to the touch, which may take a couple of days to a week, depending on humidity.
Using the Mold, Forming Your Platter
Use a needle tool to cut the excess clay around the edge (7). Roll out a long coil and attach it at the point where the well of the plate meets the flange, making sure to slip and score (8). Throw the foot until it is the desired depth, then use a rib to round off the bottom of the foot (9). You may have to use a needle tool to level the foot if it becomes too uneven after the initial throwing. Once you are happy with how the foot looks, drape the form with plastic and leave it to firm up.
Return the platter to the wheel and use your trimming tools and ribs to round the rim, making sure not to deform it (10). Leave the platter loosely draped in plastic until it is the consistency of a sharp cheddar cheese. Apply wax in quick, confident strokes with a brush, making sure to consider the layout of your design as you go (11). It may be helpful to draw the design with a soft pencil first, but bear in mind that if the clay is too soft you may leave unwanted marks. Consider waxing the foot as well; it will make cleanup after the slip application easier. Leave the wax to cure for up to one day, depending on the brand, making sure to keep the platter covered. Apply your slip by either dipping (12) or pouring. Do not attempt to clean up the waxed areas until the slip has dried enough to touch; then, gently clean with a damp sponge or paper towel.
Unfamiliar with any terms in this article? Browse our glossary of pottery terms!
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