How to Make Delicate Translucent Platters with Porcelain Slip and Terra Sigillata How to Make Impossibly Thin Porcelain Slip Cast Plates Christina Bryer

Think thin porcelain. Now think even thinner porcelain and you have the plates of Christina Bryer. These translucent plates are a slip-casting marvel but not nearly as impossible to make as you would think.

In today's post, an excerpt from the Ceramics Monthly archive, Christina walks us through the process of making her delicate, porcelain slip platters. - Jennifer Poellot Harnetty, editor

I have always been interested in geometry, and responded strongly to Roger Penrose’s aperiodic patterns when I first saw them 15 years ago. In his writing/research, I encountered pentaplexity and realized, “this is it.” In these grids, the patterns of pentagons do not tile regularly, but aperiodically. The geometry in my art is inspired by this aperiodic tiling pattern and Euclidian lace. In short, the patterns reflect the geometry of life and nature’s tendency to construct complex geometries on micro and macro levels such as DNA strands and stellar configurations. Starting with absolute grids frees one to work with infinite possibilities.

Constructing a plate takes an entire, uninterrupted working day.I begin by preparing my tools: three or four plastic bottles with different size nozzles, a jug of porcelain slip, a fine silk cloth, a firm cotton cloth, a graphic print, a brush, a wooden skewer, and ten pre-made and high-fired porcelain cones (2). I start in the morning by preparing a basic porcelain slip. For this plate I only use white porcelain slip, but one can add oxides or stains for different colors.

I soak a plaster bat in water to keep the humidity constant for a day (3). A dry bat is not a desirable surface to work on as the drying clay slip starts to flake off. I then dampen the graphic print (4) which is a master grid of 20 inches (52 cm) in diameter (I print to this size because it is the maximum size I can fit into my kiln and it can just be lifted onto a kiln shelf when it is dry without disintegrating in my hands), constructed in Adobe Illustrator and printed on archival paper. It can be re-used many times and has the added advantage of non-directional stretch (normal paper, when wet, stretches much more in one direction than the other, which will skew the pattern). I then smooth down a layer of fine, water-soaked silk on top of the print with a squeegee (5). The clay slip will stick to the paper and the layer of silk between the paper and the clay facilitates the peeling off of the paper later

Next, I use different sized nozzles (a brush or a stick will also work) on the plastic bottles to start making dots with the porcelain slip (6). I start in the middle and work toward the outer edges. As far as the final plate is concerned, I work from the front toward the back, which means that the marks I lay down first will be top most in the final product. The creative process begins when I select dots and connect the lines in between them (7).

No two plates will ever be the same as there is no prescribed sequence or plan. I let the pattern in the grid take me where it wants to go; in other words infinite variations or interpretations are possible—every decision and every mark I make affects the final outcome. I work on the pattern from one position, turning the wheel to work on new sections. I find that working on a potter’s wheel or a banding wheel makes it easier to avoid smearing the marks I have already laid down.

After completing the whole pattern for the plate, I spray it at an angle with terra sigillata to enhance and bring out the pattern (8). I then cover the whole back with a thicker porcelain slip layer that forms the basis of the plate (9–10). I fill in each section individually rather than pouring one single layer, this way the slip follows the pattern, making the back reflect the front. Trial and error have taught me that 2.2 pounds (1kg) of mixed slip is sufficient to cover my 20-inch (52 cm) plaster bat. I let the plate rest for at least three hours until it is no longer tacky. I then cover the plate with a layer of silk plus a layer of firm cotton to facilitate ease of handling. The cloths prevent the bat from sticking to the clay, the silk leaves hardly any imprint on the clay, and the cotton cloth adds strength. I now cover it with a light plywood bat, flip it over, and peel the silk up and away from the porcelain (11).

The result is a porcelain pancake resting on top of two layers of cloth. (I re-use the cotton, silk, and paper over and over again.) To make a mold for these cones, I slab build a cone to the desired slope and size. When it is leather hard, I refine and finish it, then make a plaster cast. I dry the plaster mold for several days and then cast porcelain slip into it. I usually make ten cones from the same mold and fire them to cone 9 (12). The reusable, slip-cast, high-fired porcelain cones now come into play. I lift up the decorated porcelain slab by gently pulling the bottom cotton cloth upward and pushing ten porcelain cones underneath to create alternating humps and slumps (13).

The plate is now left to dry completely, which can take up to several days depending on the weather (14).

Once it is dry, I carefully remove the cones and tug gently on the silk until the porcelain is completely free. The silk tends to stick very slightly to the dry porcelain but comes away with gentle tugging. For maximum support, I place my open hands under the porcelain and gently lift the plate onto a kiln shelf. I re-insert the cones under the plate for the firing (15).

Each cone is dusted with alumina to prevent it from sticking to the plate during the firing. I fire the plate to 2300°F (1260°C). The finished thickness can vary slightly but my pieces are about 1–2 mm thick and about 17 inches (42 cm) in diameter and quite translucent (16).

To see more of Christina Bryer’s work go to www.christinabryer.com.

**First published in 2013