Today I live in a small artist community in historic Helper, Utah, two hours south of Salt Lake City, where I maintain my studio. After the 2008 recession, I left my academic career and developed a new line of porcelain dinnerware using a 12th-century Korean decorating technique called mishima. I incise a design into the surface of a pot, fill it in with a contrasting colored clay or slip, and then cover it with a transparent glaze. I combine my deep passion for modern design and simplicity to create beautifully balanced and unique dinnerware that seamlessly blends tradition and innovation. 

Finished indigo inlaid plate by Kathleen Royster.

Applying a Pattern

Begin by forming a wide bowl, platter, or serving dish. Allow the form to firm up to leather hard. Drawing on leather-hard clay gives a clean line, whereas bone-dry clay delivers a ragged line that makes it difficult to inlay color cleanly. I use a cone-10 porcelain without grog. Any clay can be used, but keep in mind the finer the clay particles, the crisper your lines will be.

1 Cut out several stencils using paper or hobby foam. 2 Small loop tools give wide lines while an X-Acto knife creates thin lines.

Next, cut out stencils using paper or hobby foam (1). I like hobby foam because it resists water, so the shape can be used multiple times. The shapes I use are simple, and when used, you begin to make patterns. A straight line vs. a ragged line gives a very different feeling. There is beauty in repetition. 

3 Using a wider mark-making tool to create a definitive, bold line. 4 Use an X-Acto knife to yield a concise line and create an interior pattern.

Gather several mark-making and carving tools (2). Your mark-making tools can vary in width for different effects. Try loop tools for wider, bold lines (3). Use an X-Acto knife for thin, concise lines (4). Before you start carving, try propping your piece up at eye level. This will help you draw straight lines. As you carve, pull downward toward you, letting gravity help you draw straight lines. If you make a mistake or change your mind, use a metal rib to compress the clay back to its original surface.

Complete your carving and let your pot dry completely to bone dry. Once dry, you can brush off any burs with a relatively stiff brush before beginning to add slip 

Prepping Slip

There are a couple of options for creating slip: you can use a commercial underglaze or make your own slip. I like to use the clay trimmings from my throwing wheel, so I have less waste. Using the same clay body together, in the pot and the slip, promotes a better fit between the materials with less chance of cracking occurring during drying or firing. To use your clay trimmings, allow them to fully dry out. Then, slake them down in water. Fill a bucket partway with the trimmings, add enough water to just cover the clay, and allow the mixture to set overnight or until you have the consistency of pudding. If you have too much water, it will rise to the top and you can scoop it off. Or, you may need to let the entire mixture evaporate until you have a thick, but brushable consistency.

5 Use a commercial underglaze or make your own slip. Add stains for color. 6 Use a brush to work slip into the cuts, creating a layer level with the surface.

When making your own colored slip, Mason stains (www.masoncolor.com/stains) provide a stable option. Note: Some stains burn out at high temperatures (mostly pinks and reds). Mason has developed an encapsulated stain that protects the pigment so you can use them at any temperature. 

After slaking down the clay, add 10–15% stain into the slip (5). Be sure to screen the mixture for even consistency. The amount of stain you add is up to you and how deep you want the color. Test your slip and stains on pre-made and fired test tiles with sample carvings. Depending on the width of your lines you may need to adjust the thinness or thickness of the slip. Thick lines will require a thick, pudding-like viscosity and thin lines need a watery slurry.

Inlaying Color

Using a Japanese paintbrush, work the slip into the cut until you’ve built up a layer of slip even with the surface (6). I use a Japanese brush because it holds a lot of slip and the tip allows me to direct slip into the cuts. The more you work with this technique, the easier it gets. 

7 After covering the entire surface in a level layer of slip, let the pot fully dry. 8 Once the pot is dry, take a wet sponge and gently wipe the slip off the surface leaving the contrasting slip in the cuts.

Allow your pot and the colored slip to dry out again to bone dry (7). Remember, working in ceramics is truly the art of moisture management!

9 Removing the colored slip reveals the clean, inlaid lines of your design. 10 Let the piece completely dry, bisque fire it, apply a clear glaze, and fire to desired temperature.

Once your pot is dry, take a damp sponge and gently wipe the slip off the surface leaving the contrasting slip in the cuts (8, 9). This step leaves clean lines of your design (10). Let the piece dry and bisque fire it to cone 04.

Finally, apply a clear or suitable transparent glaze to the bisque-fired piece, then fire it again to the desired temperature appropriate for your clay body. 

Finished indigo inliad bowls by Kathleen Royster.

Kathleen Royster earned an MFA from the University of Utah, where she was awarded the Ethel Rolapp Award. She is a former art professor at the Metropolitan State University of Denver and Scripps College, and a former board member for the National Council on Education for the Ceramics Arts (NCECA). Her teaching and research interests include historical and contemporary ceramic history, 20th-century design history, and the place of design in culture. To see more of her work, visit www.kathleenroyster.com or follow her on Instagram @kathleenroyster.

Unfamiliar with any terms in this article? Browse our glossary of pottery terms!
Click the cover image to return to the Table of Contents