Contrasting Aesthetics and Textures Gillian Parke

Appears in the Sept/Oct 2018 issue of Pottery Making Illustrated.

In 2004, I took a workshop titled “Color and Line” with Rimas VisGirda to learn about luster glazes and other materials used in the decoration of fine china. Prior to this, I worked as an organic chemist in pharmaceutical research and was intrigued with the chemistry of overglazes. One of the pieces Rimas showed us during the workshop was a small sculpture of a man from the waist up with a tiny head. There were eruptions on the surface from decomposed granite that he had added to his clay. I was awestruck. This was the start of my artistic pursuit of combining contrasting aesthetics and textures into completely integrated pieces.

After much experimentation, I was able to throw porcelain with feldspar and molochite inclusions and alter the forms with the addition of plain porcelain parts. Throwing with inclusions in the clay is difficult. If there isn’t enough water, fingers will catch on a piece of feldspar and the clay will rip when raising the walls. Too much water can saturate the clay and the piece will collapse. Another issue is that flat, sharp pieces of feldspar can cut through your skin. I’ve found that using a thin, natural sponge covering my right finger while pulling up adds the right amount of water and protects my finger from the feldspar. For larger pieces, I throw in stages, allowing the clay to dry a bit after 5 or 6 pulls. It’s also important to use a metal rib to remove excess slip that can further saturate the porcelain.

My decanter is made from four separate pieces using two different clay bodies. Helios porcelain (from Highwater Clay) is used for the bottom, top, and stopper. For the body of the decanter, I use Helios porcelain with coarse feldspar and molochite inclusions. I purchase Custer feldspar (1-10 mesh) directly from Pacer Minerals as it’s no longer available from my local supplier.

Body of Decanter

Weigh 3 pounds of porcelain and add approximately ⅓-cup of coarse feldspar and a tablespoon of molochite to it (1). Before wedging, spray the mixture with water to hydrate the additives and prevent the clay from becoming too hard. After wedging, cut through the piece to check that the feldspar is equally distributed (2).

Center the porcelain on the wheelhead to create a bottomless ring (3). Throw a conical form with the top narrower than the bottom. Make sure water is added before each pull and use the sponge to remove excess water that settles in the bottom. If the clay becomes too saturated with water, remove the slip, and set the piece aside to dry before continuing.

Before altering the body, use a metal rib to remove any slip on the outside. This helps expose the feldspar and create drag lines. Additional drag marks can be made by using a trimming tool to remove the outer layer of porcelain, starting at the bottom and slowly pulling up to the rim while the wheel is turning. To form a square, first cut the base off the wheel while the wheel is turning. This helps it to hold its shape. Next, use a triangle with a right angle as a guide and draw lines where the corners will be formed (4). While the clay is wet, run a wet finger up the inside along the lines. Push the clay out to make four corners and gently press the sides into a square (5). Set the piece aside to d ry.

Bottom and Top

Measure the bottom opening with calipers and roll out a ¼-inch-thick slab of porcelain that’s slightly larger than the opening. Use a soft rib to compress the clay flat.

Center 1 pound of porcelain and open to create a bottomless ring. Pull the sides up and in, using slightly more pressure with the outside hand while the inside hand guides the clay toward the middle. After each pull, collar the top gently to make the opening smaller (6). Once the opening is approximately 1 inch wide, pull the clay directly up to create the opening for the stopper, about 1 inch tall. To create the stopper gallery, gently squeeze the bottom of the opening (7). Measure the top with calipers to make sure that it’s bigger than the opening of the decanter body.

Stopper

Since the stopper is relatively small, it’s easiest to throw off the hump. Center a small section of a lump of porcelain on the wheel. Make a small hole in the middle, about 1 inch deep, widen it slightly, then throw a conical shape, and cut it off the hump (8).

Assembling the Decanter

Due to the feldspar and molochite inclusions, the shrinkage rate of the two porcelain bodies are slightly different and precautions need to be taken to prevent cracking at the attachment points. To ensure the moisture content of all the pieces equalize, stack the parts together (9) and cover them with plastic for at least 24 hours.

The joining slip is made by soaking 2 cups of dried porcelain scrap and 1 sheet of shredded paper towel in Lana Wilson’s Magic Water (1 gallon water, 9.5g sodium silicate, 3g soda ash). Leave the mixture overnight, then blend using a hand blender. The added paper retains water and allows the joint to dry out more slowly, which prevents cracks from forming between sections made from porcelain containing inclusions and those made using plain porcelain. Attach the pieces when the parts are in a firm, leather-hard state.

To prepare the slab, use a pony roller to taper the edge. Score the slab and place it on the bottom of the body that has been scored and slipped. Use the pony roller to press the pieces together and roll the edge of the slab onto the outside of the body (10). To further incorporate the two pieces, paddle the edge of the slab onto the outside of the body, and add a coil to the inside seam. Using a Surform and serrated and flat metal ribs, remove the excess clay from the outside seam (11).

Flip the top upside down and secure it inside the base. Use a round Surform to remove excess clay from the inside of the top, then square the outer edge slightly to make it more closely match the body (12). Score and slip the top’s edge and the top of the decanter body (13) and attach. Check that it’s on straight using a level. Smooth and compress the attachment using a pony roller and paddle as described above. Use a Surform to remove excess clay from the top. Score and apply slip to the gap where the two pieces overlap and attach a coil of the porcelain with feldspar inclusions (14). Use a Surform and a serrated rib to remove excess clay and create a seamless transition.

Place the finished decanter on the wheel and center the top. Put the stopper in place and shape the end with a trimming tool (15).

Decorating and Firing

When the decanter is bone dry, draw decoration on the four sides in pencil. Paint wax resist onto areas that will eventually be glazed, then apply underglaze to the unwaxed clay areas. Partially remove the underglaze from the surface with a damp sponge, leaving a patina that accentuates the feldspar and throwing lines. Apply wax resist to the dry surface, then using a needle tool, etch lines through the wax, revealing the clay below. After wiping clean with a damp sponge, apply black underglaze to the inlaid lines.

After bisque firing to cone 07, apply wax resist to the black inlay lines so that glaze won’t cover the lines and affect the color. The resulting piece is fired in a gas reduction kiln to cone 10.

The feldspar inclusions result in pearl-like eruptions on the vessel’s surface. This surface is painted with various layers of luster overglazes and fired in an electric kiln to cone 017 multiple times.

Gillian Parke lives in Durham, North Carolina, with her husband and two children. Her work is in numerous public and private collections including the San Angelo Museum of Art and the Mint Museum in Charlotte, North Carolina. Learn more at gillianparke.comand CharlieCummingsGallery.com .