In the Potter's Kitchen: Bisque-Molded Basin Rhonda Willers

Appears in the Jul/Aug 2020 issue of Pottery Making Illustrated.

I prefer working with handmade bisque molds to make my individual pieces. My basin bisque mold is the largest one in my studio. It’s a generous form that offers a variety of uses, both decorative and utilitarian, and is the perfect serving piece for a hearty salad.

Quick Bisque Molds

I like to make my bisque molds quickly, and to do this I found working with fat coils (1–1½ inches diameter) speeds up the process. To begin making a dome shape, lay the first coil down on a ware board creating the outline of the shape you want to make. Score between layers (if the clay is still moist, slip isn’t necessary), then add the next coil. After two layers of coils are added, use a metal serrated rib to blend the coils together followed by a medium to soft polymer rib to smooth the surface. Continue adding coils, slightly tapering them inward, and repeating the scoring and smoothing processes until you reach the top and closing point of the form. After the form is closed in, use the serrated rib to smooth the entire surface. You’ll notice the form has tension because of the trapped air between the clay and the ware board. If needed, you can fill the interior space with newspaper, foam, or plastic (which I like to use as it won’t dry out the form prematurely). Once the form is a medium leather hard, use a Surform rasp to even out the surface, then smooth it again with a soft rib before allowing the mold to dry. Fire the dry mold to the bisque temperature appropriate for your clay.

Throwing Larger Slabs

My basin’s final dimensions are 16 inches in diameter × 5½ inches high. To create a slab large enough for this surface area, begin with about 10 pounds of wedged clay. Throw the slab out on a firm table-top surface, or use your studio floor with a 24 ×24-inch or larger piece of smooth plywood or similar material. Be sure you have enough room to freely move your arms as you throw the slab. A good toss makes an airy whoopf sound, implying that a gentle landing occurred with one edge of the slab hitting the table surface first and the rest of the slab following, stretching as it landed (1). In contrast, when you hear a harsh slapping sound as the clay lands, it’s a bit like a belly flop in the water where the clay slab surface lands flat on the tabletop and doesn’t stretch.

After the clay is stretched enough that it will cover your mold, use a serrated rib (optional), followed by a green, medium firmness polymer rib to smooth and compress the surface while removing air bubbles that may have formed during stretching. Now, place the slab on a ware board and move to an area closer to your mold.

Fitting the Slab to the Bisque Mold

Prop the bisque mold up on a support form. I often use an empty container that is sturdy enough to support the weight of the larger form. Tip: Set the mold and prop on a banding wheel to make the slab fitting process easier.

Trim the slab to best match your mold form, with a little extra room to for the slab to overhang the mold. Using your forearm and opened, flat hands, gently move the slab so it lays across one arm as you carry the slab over to the bisque mold (2). Lay the slab down and use your palms to slowly work the slab down from the top of the mold to the edge of the mold (3). Use the serrated metal rib to compress the slab and even out its thickness (4). Follow with using a very soft polymer rib to smooth the surface.

Allow it to set up for a half hour or so, reaching a soft leather hard before using a fettling knife to trim the edge of the slab just above the edge of the mold (5).

Separate the Mold and Slab

Using your fingertips, softly lift the edge of the slab away from the bisque mold. This makes removing the mold easier. Using a piece of foam on your arm or on a ware board/tabletop, flip the mold onto the foam surface (6). Set the flipped mold onto a table surface with the foam piece between the mold and tabletop. Lift the mold away from the clay slab (7). If it feels stuck, you can either flip it back over and wait a bit longer, or you can try to loosen the edges of the slab against the mold. After you remove the mold, if the clay feels soft and not quite ready to hold its form, you can wrap some plastic or a towel around the base of the form, below the foam layer, to provide extra support while the clay firms up (8).

Finishing the Rim

After the form is flipped, use a fettling knife to trim the rim edge line to what you desire. When I work a basin form’s rim, I’m often thinking about the rolling hills I see outside my studio window and on my drives through the Wisconsin countryside. While the clay is still malleable, but not sticky, pinch or finish the rim to your liking. As you work on the rim, have the form on a ware board with a banding wheel below to allow smooth movements. After you pinch the rim, use the tip of your index finger to slightly smooth the edge ever so gently so as to not dent the pinched line, but smooth out any micro bumps (9).

Finishing Process

Allow the basin to fully dry. Then, I brush on three layers of my blue/black terra sigillata (see recipe, right). I bisque fire the basin to cone 04, then brush on a soda ash/water wash (1 part soda ash to 3 parts water), and fire the basin again to cone 03 in an electric kiln. To finish, sand the basin with 800-grit wet/dry sandpaper in water.

Rhonda Willers is the author of the book Terra Sigillata: Contemporary Techniques, which is available from the Ceramic Arts Network Shop at https://mycan.ceramicartsnetwork.org/s/product-details?id=a1B3u000009udqnEAA.