Stenciling on Clay

My creative process proceeds not from form to decoration, but in reverse. I start with the development of a graphic surface pattern, which I create and refine on my computer using Adobe Illustrator. I play around with scale, layering, and color until I have a pattern I love. The pattern is the jumping-off point for the creation of a vase, cup, plate, or other form.

My patterns are derived from an abundance of influences, including Islamic architecture, Eastern European textiles, Japanese woodblock prints, and traditional American quilt designs. The process of bending and stretching a traditional motif into new and surprising patterns is part of the joy of beginning a new piece for me.

Making the Stencil

Once I have developed a pattern, which might include as many as six layers of color, I create a corresponding number of individual stencils from Dura-Lar, a polyester film available from art supply stores and online. Stencils can be cut by hand using a sharp blade, or you can use a die-cutting machine for greater precision. Pre-made stencils can also be purchased at craft stores or ordered online, and there are even companies that will custom cut your stencils for you.

When choosing your first pattern, start with a simple 2-color design, and then as you become more familiar with the process, you can move on to more complex patterns of 4 or more colors (I usually use 3–5 colors).

Colored Clay and Slip

I get color inspiration from a variety of places, in particular the seasonal changes in my garden, as well as color combinations that I find myself drawn to in textiles, tile work, or other forms of art.

A white clay body works best for this project. I purchase clay in dry form, add Mason stains for color, and then mix it with water to make a slip. I reserve a portion of that slip mixture as printing material and I dry the remaining portion on plaster bats to create colored clay. I create all my colored clays and slips this way, usually in 5-pound batches, and now have a library of over 100 colors to choose from when I begin designing a new piece.

1 Roll a slab and cut out the front and back of the vase using a template.

2 Place the first stencil on the slab and adhere it with a pony roller.

The Form

Once I have chosen my pattern and colors, I’m ready to think about form. I have some forms, especially cups and mugs, that I use over and over because I find them satisfying and they can accommodate a variety of patterns. For vases and other large pieces, I often create a form that mirrors some element within the pattern, for example in the shape of the handle or the curve of the belly.

For this vase, I created a simple template for the body and another for the bottom, both cut from reusable tar paper. The template is 7 inches tall by 11 inches wide to make a vase that will be 6×10 inches. The handles of my vase are incorporated into the template for the body of the form, meaning that the handles are not added on later, as is often the case, but rather they are part of a single slab, along with the body.

Begin by rolling out a slab of violet-colored clay (or a color of your choice) to approximately 3/16 inch thick and wide enough to cut out the two sides and the bottom, then cut out the three pieces using the templates (1).

Printing

Printing is my favorite part of the process, because as I layer the colors and patterns, I begin to see the composition of the surface come alive.

Lay the first stencil on the clay and press it gently with a pony roller to create a bond between the damp clay and the stencil (2). This prevents slip from leaking under the stencil, and is essential to getting a crisp pattern. Next, apply colored slip onto the stencil using a large stiff brush. The slip should be the consistency of icing, and should completely cover the parts of the slab exposed by the stencil (3). One coat is adequate as long as the slip is fairly thick. The slip coating should be thick enough that the outlines of the stencil are no longer visible, which is to say the slip is at least as thick as the stencil itself. Immediately after application, gently smooth the slip using a soft red rib to eliminate excess slip and create an even surface (4). Lift the stencil off the clay (5). Voila! You have a pattern. Set this piece aside to dry a bit while you are printing the second side and the bottom.

3 Using a large stiff brush, apply slip through the stencil.

4 Use a flexible rib to remove any excess colored slip.

5 Lift up the stencil then repeat on the second side and the bottom piece.

6 Dry the first side with a cotton cloth and a pony roller. Print the remaining layers.

For the second pattern layer and color, start by laying a clean piece of cotton cloth (an old bed sheet torn into pieces works well) over the slab and roll it gently to compress the pattern into the clay and absorb any excess moisture that might cause the stencil to stick and smear (6). Repeat the printing process for a second, third, and subsequent layers of pattern and color on both the front and back pieces of the vase. I line up layers by eye, but you could add registration marks to ensure consistent and accurate alignment. Tip: If you wish (and I always do), you can also print the same or a different pattern on the inside of the vase.

Once the printing is complete, wrap each section of the vase in a damp piece of cotton cloth and then in plastic. Let the pieces rest for at least an hour, but you can leave them overnight or even longer before you build your vase. This step is very important in order to rehydrate the clay before manipulating it.

Hump, Slump, and Drop Molds

In addition to stencils and colored clays and slips, you’ll need a hump, slump, or drop mold to give the vase volume. I generally prefer hump molds, because they allow me to see what is happening on the outside of the vase. I formed a funny looking vase shape out of clay and bisque fired it to create a hump mold that works well for this particular vase (7).

7 Prepare and bisque fire a hump mold to shape the vase form.

8 Trim the pieces using the template. Mark the handles on one of the pieces.

9 Press the slab onto the bisque mold. Once it firms up, repeat with the second side.

10 Lay both curved sides on foam, facing up, then score and slip the edges.

Forming the Vase

Unwrap one side of the vase, and lay a piece of cloth on it to absorb excess moisture and prevent smearing of the pattern. Next, place the tar-paper template on top of the printed slab and trim the edges. It is critical that both pieces of the vase body are exactly the same size so they will fit together well. Use a needle tool to outline, but do not cut out, the interior of the handles on one of the two pieces (8). Place your bisque-fired hump mold on a ware board and carefully lay the first side of the vase body on the mold (9). Gently press the clay onto the mold, making sure the handles are flat and the mold is centered. Allow the clay to firm up until it can be lifted from the mold without losing its shape. Set it aside and repeat the process with the second side of the vase. Cover both sides with a single piece of plastic and allow them to set up overnight.

Assembling the Vase

Lay both sides of the vase on a piece of soft foam with the interior surfaces facing up. Carefully score and slip the edges and handles (10). Tip: I use water instead of slip to minimize damage to the printed surface. Once both sides are prepared, stand them upright and carefully press the edge surfaces together, including the handles. Make sure you have good contact and bonding from top to bottom. Remove any excess clay from the edges of the vase (11). Flip the vase over and ensure that the bottom corners are securely joined.

11 Stand both sides facing each other, line them up, and press the edges together.

12 Trim excess clay from the edges. Cut out the handle interiors with a sharp knife.

13 Set the vase on a slab, trace around it, score, add slip, then attach the base.

Next, flip the vase right side up again and carefully cut out the interiors of the handles, following the outlines you marked earlier (12). Make sure the handles are properly lined up with the body of the vase.

Wrap the entire piece in plastic and allow it to set up to leather hard. Once your vase has firmed up, set it on the bottom piece, which has been allowed to dry to the same leather-hard stage. Trace the bottom edge of the vase on the bottom piece (13), then score and slip both pieces and press them together. Flip the vase over and run a pony roller across the bottom a few times to ensures that the bottom is well adhered to the vase body before trimming. Complete any final refining and smoothing.

Caution: Because of the printed pattern, the surface of the piece should not be sanded after bisque firing, so take extra care with smoothing and cleaning up your surfaces before firing. Allow the vase to dry slowly under plastic before bisque firing.

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14, 15 Heidi Tarver’s Lavender Fan Vase (left) and detail (right), 10 in. (25 cm) in height, white stoneware, clear glaze, fired in an electric kiln to cone 5. Photos: George Post.

Glazing

After the vase emerges from the bisque firing, all the hard work is already done. You may want to lightly wet sand the edges of the piece to soften them, but be careful not to sand away the pattern.

Finally, apply a thin coat of clear gloss glaze, pouring it into the interior first, then brushing the exterior with 2–3 thin coats, then fire it again (14, 15).

Heidi Tarver makes art and designs gardens in Northern California. She is obsessed with geometric patterns, and has never met a color she didn’t like. To see more of her work, visit www.heiditarver.com, and follow her on Instagram @heiditarver.

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