Compressed Slab Bowl

I’ve found that handbuilding using a compressed slab to form plates and bowls ensures that the form will be less likely to warp. The inspiration for making these forms came from wanting to be able to make a bowl that could be completed within one day, including creating the foot and adding any surface decoration, like carving and slip application.

Preparing and Compressing the Slab

Start by rolling a basic slab, 12–14 inches in diameter and 3/8 inch thick. Use a template or a bat to cut a circle out of the slab. Drape it over an inverted, footless bowl that was bisque fired to two or three cones lower than the clay body’s maturity (see 1). This creates a surface that absorbs moisture from the slab and also allows you to cut the design out without damaging the bisque mold’s surface. If the slab gets distorted a bit from transferring it to the mold, it doesn’t seem to affect the end product.

To thin and compress the clay on the mold, start by rolling a piece of rubber tubing (1) and/or a baseball bat (with the lacquer finish removed) across the surface. The tubing is flexible with a good feel for the pressure applied to the clay, and will slightly contour to the form. Start by rolling across the middle of the slab and then roll out toward the edge. This helps stick the slab to the mold so it won’t slide around and also helps to establish the thickness of the bottom. Once the slab is compressed and thinned out, add water to the surface and pull a rubber rib across in a variety of directions while pressing down against the mold to compress the clay and also help to even it out (2). Next, run a damp sponge across the surface. At this point, the final shape for the rim can be cut and smoothed with a sponge.

1 Bisque fire a clay hump mold. Place a slab over the mold. Compress and thin the slab using a length of flexible plastic tubing.

2 Spray water onto the slab, then use a flexible rubber rib to compress and even out the slab.

3 Use a pre-made plastic template to cut out a shaped slab for the bowl’s foot.

4 Use a flexible tape measure and dividing lines made on the mold to determine the foot’s placement.

Attaching a Foot

The templates I use to make the foot are cut out of flexible plastic place mats (3). Adhere the foot onto the bowl right after it’s smoothed out. To center the foot on the bottom of the bowl, line up a flexible tape measure across the bowl following dividing lines that are marked on the mold (the black lines divide the mold’s surface into halves, then into quarters, then into eighths, while the red lines divide the surface into thirds). Using the tape measure as a guide, draw a light pencil line on the clay (4). After drawing several lines, measure the length and width or diameter of the foot, mark these dimensions on the bowl (measuring from the center point), then square up the corners of the slab foot with the pencil lines (5).

Score the bottom of the bowl where the foot will be attached, as well as the back of the foot, then apply slip and attach the two together. Clean up the seam, then use a pony roller to create beveled curves along the outer edges of the foot, stopping just before reaching the corners (6). Next, alter the interior of the foot using a small, domed bisque mold to create an indentation (7). Use a stamp to create an area of textural detail in the center of the foot (8). Finally, clean the seam with a damp sponge.

5 Using the pencil lines as a guide, square up the edges of the slab foot.

6 After attaching the foot, use a pony roller to bevel the interior sections of the outer edges.

7 Use a small, domed bisque mold to indent the center of the foot.

8 Stamp the middle of the foot with textural detail.

Adding the Finishing Touches

While the bowl is still on the mold, add surface decoration to the exterior. I use additional flexible plastic templates to delineate areas where I will add carved textures (9). After marking these areas, use a variety of loop trimming tools to create the outlines of the shapes and to add some texture reminiscent of planished metal (10).

When the clay is firm enough (leather hard), flip it over and do additional carving or other types of decorating on the bowl’s interior. To remove the bowl from the mold, gently pry up along the edges and it will pop off. Because the clay is firm enough at this stage, it’s easy to flip over with only minimal distortion, if any.

8 Delineate areas for added textures using a flexible plastic template.

10 Carve textures inside the outlined areas using small loop tools.

11 Use templates to decorate the interior, then refine the lines.

12 Remove any sharp edges and burrs by lightly running a damp sponge across the surface.

Carving the inside is fairly easy; if necessary, support the bottom with your hand as you work, or work on a soft piece of foam. Use the shape of the rim as a guide when defining areas for texturing and when placing design motifs. Trace around and over paper (11) and plastic templates of different shapes to create a composition, then go back over the traced lines with a small trimming tool to accentuate them. After carving the surface, smooth sharp spots and remove burrs by lightly running a damp sponge across the surface (12).

Leo Peck lives in Napa Valley, California, where he maintains his business, ClayLights (http://claylights.com). He has worked with clay for over 35 years, starting as a functional potter, followed by exploring tile, furniture, and translucent porcelain lighting.

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