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Published Mar 12, 2012

Happy Monday readers! We're back (after a slight hiccup with our server)! And I have a great post for you.

Today, Ben Carter tells us all about a cool platter forming technique in which he uses tar paper, slump molds made from insulating foam and hand sewn cloth forms filled with grog. Ben also shares his sgraffito and painted colored slip decorating process. - Jennifer Poellot Harnetty, editor

An interest in creating a sense of value through decoration, along with the ability of that decoration to craft meaning led me to work with earthenware. This might seem contradictory, since earthenware has common and utilitarian associations, but the choice is based very much on the history of the material.

The perceived value of earthenware has shifted throughout time. As a variety of techniques were explored, the level of decoration and experimentation increased. Major aesthetic breakthroughs occurred in the wake of the attempt to mimic porcelain. By covering earthenware with white slips or glazes, the objects also benefited from associations that porcelain had in the culture.

Making Templates and Molds

I begin by making a template in the shape and pattern of the rim of the platter, creating the template using tar-paper. Tarpaper can be used repeatedly because it’s impervious to water. Cut the interior section of the template at both ends for easy registration on the form (figure 1).

Next, create a slump mold from stacked layers of closed-cell foam (the kind used for home insulation). The thickness of the mold depends on the depth of the recessed area required in the finished piece. I’d suggest making the mold at least 3 inches thick for strength. Mark the outline of the template onto the top of the stack. Individual sheets can be secured together using double sided tape. To create the recess in the slump mold, measure 1½ inches in toward the center from the two long ends and the two middle lobes of the outline and make a mark at each spot. Draw an oval connecting the dots, then use a serrated knife to cut out the shape.

Use the tarpaper template to aid in creating small cloth forms that sit on the rim of the foam mold (figure 2). The cloth forms are comprised of eight semi-circular sections that form a wavy rim for the platter. Make each cloth form using two pieces of canvas sewn together and filled with heavy grog. Pin the thinnest edge or point of the cloth form to the foam using T-pins (figure 3).

Making a Platter

Cut a 3/16-inch thick slab using the tarpaper template. Bevel or soften the edges of the slab and use a soft rubber rib to compress each side of the slab in both directions. Place the slab onto the stacked cloth and foam forms so that the slab edge lines up with the outside edges of the cloth form. Work the slab into the form using a soft rib and working both from end to end and side to side (figure 3). The advantage of this form is the ability to bend the slab on more than one axis, so take time to work the clay down into the curves.

Let the slab firm up to a leather-hard. Place a bundle of soft padding and the section of blue foam that was removed earlier into the platter’s interior. Flip the whole stack over (figure 4). Make sure the rim rests parallel to your work surface and is elevated a few inches above it.

Extrude, handbuild, or throw a ring to form the foot. Curve the wall of the foot into a slight “C” shape with the curve flaring away from the center of the piece. Try to match the volume of the foot to the volume of the rim. Allow the foot to set up to the same leather-hard consistency as the piece before attaching it by slipping and scoring (figure 5).

Slipping and Sketching

After the foot has set up and can hold up the rest of the platter without slumping, flip it over and remove the padding and foam. Smooth out any marks made by the foam. Apply a base coat of white slip to the bottom and rim. Apply the slip by pouring it into smaller pieces and spraying larger ones. You can also paint the slip on using a brush. Allow the piece to dry between coats. Brush the interior surface of the form with colored slip, about the consistency of yogurt (figure 6). Note: When slipping greenware pieces, it’s very important not to load the piece with too much moisture.

Once all the slip coats have dried, sketch a pattern or design onto the interior of the piece with a dull pencil (figure 7). Sketch lightly so the composition can be easily painted over if desired.

Brush colored slips, the consistency of pudding, into the drawn pattern (figure 8). Create gestural movement with your brush and the thicker slip by making quick direct strokes. Work from dark to light colors, allowing the dark slip to show behind the lighter slip and ultimately creating translucency and depth.

Use the sgraffito technique, scratching through the layers of slip to expose the clay body underneath. When fired, this dark line provides contrast to the lighter colored slips. If less contrast is desired, you may scratch through only the top layer of slip to expose the bottom layer. This line, whether high or low contrast, deep or shallow, works to sharpen the edges of the brush marks.

The timing of the sgraffito work affects the line quality. The moisture level of the clay should match the size of the tool. Start with the widest tools when the clay is a soft leather hard. As the pot dries, make finer lines with finer, sharper tools. For wide lines, use a chopstick sanded to a dull point. For small lines, use X-Acto blades and needle tools (figure 9).

Topics: Pottery Clay