Handbuilt Envelope-Style Vessels Rebecca Zweibel

Appears in the Mar/Apr 2018 issue of Pottery Making Illustrated.

I began my ceramic arts career as a thrower making functional wares, beginning with my first pottery class years ago in Colorado. Porcelain was my clay of choice, and my goal was to get thinner, higher, and lighter with every piece. I still love the pristine, bone-like look of fired porcelain, but found that my love of color and drawing was not satisfied. The switch to earthenware and handbuilding came gradually, with spates of slab work interspersed with my continued throwing. My current work has a decorative emphasis with a lot of sgraffito and color, and I love making primarily unique forms that help inspire how the piece is decorated. For several years now I’ve been using Earthen Red from Highwater Clays, which has a wide firing range. The dark color adds depth to the surface treatments I like, emphasizes the dark lines of sgraffito, and I find it easy to work with.

Slab Construction

Slab construction is my main form of handbuilding, although I occasionally use bisque molds to create bottoms for pieces. Cement backer board (see 8) is a big help as a surface to work on; it’s thin, light, and durable—and doesn’t have the paper coating that drywall has, which tends to peel off onto the slab if the clay is too wet. Drywall also may crack apart if you’re using it to carry a heavier piece. With cement backer board, there is no risk of contaminating your clay with plaster bits, and the board is very efficient at drying out the clay, which is beneficial in humid Florida where I now live.

Begin by rolling out two slabs approximately ¼ inch thick. Be careful to rib and compress the slabs in all directions and on both sides, and leave them to stiffen up to a medium leather hard. The slabs can be covered lightly with plastic and left to dry on the cement backer board overnight.

Since I typically make envelope-style vessels, I only have two slabs to join at the seams, along with the bottom of the piece, which I attach later. This is where the creative part begins for me. I almost never make the same vessel form twice; I find it much more exciting to see what I can come up with when presented with a new shape and a blank surface. Stack the two slabs on top of each other (1) and use a blunt pencil to begin drawing shapes on the slab, erasing with a rib and redrawing until you find something that appeals to you. I look at historic examples and other artists’ works for inspiration. My tallest pieces are about 18 inches in height; beyond this, they become too unwieldy.

Once you’ve created a design that interests you, carefully cut through both slabs at the same time, making sure to keep the knife vertical to the clay as you cut. If the slabs are large enough, save the extra cut-off parts to form the bottom of the piece.

Take the top slab and flip it over (2). Remember, the two pieces need to fit together, so you need to make sure you’re working on the correct side of the slab. Cut all the seams that will be attached to each other at a 45° angle (3), then score each beveled edge. I apply magic water to all of the seams that will be joined together; it really helps in attaching them. Use a rib to create volume in each slab before they are joined (4). Roll several large, soft coils of clay and add them to the edge of one of the slabs (5), then stand the pieces upright, curve them toward each other, and gently squeeze the two edges together (6). Using large clay coils for the seams allows me to go back and paddle the piece then shape it with a Surform later without cutting into the seam and having the piece crack or fall apart. When joining, I prefer to start at the top and work my way down, but often I need to join the very bottom edges of the slabs early on to ensure that the piece will stand. Continue to add large, soft coils to all areas that join together, working on the inside of the piece, reaching up through the open bottom, or down from the top, if it’s accessible. Smooth the coils on the inside of the piece. Use a wooden paddle to assist with attaching the sides to each other.

At this point, reach inside and begin pushing out the piece on each side to add volume, using a rib or just your hands. In very small areas or in places that I can’t reach, I use a tool that I’ve made consisting of a wooden chopstick with a round wooden ball that I got at the craft store glued to the end (7). Cover the piece with plastic and let it rest overnight, allowing the moisture in the clay to equalize.

Fitting a Bottom

For the bottom, make a slab that is larger than the bottom opening of the piece. Cut out the shape you need, leaving an extra ½ inch or so around the outside edge of the vessel. Score the bottom edge of the piece and the corresponding area on the slab. Apply magic water to the scored areas and attach the bottom slab to the piece, folding up the bottom slab on the outside of the vessel all around (8). Paddle the bottom and sides of the piece where they’ve been joined. This will help ensure that the bottom slab doesn’t crack where it’s attached to the sides of the vessel. Once again, let the piece rest under plastic overnight.

Refining Surfaces and Edges

Next use a wooden rib to sharpen and define the edges of the surface where they’ve been joined, then use a Surform to even out all surfaces. Smooth the vessel and let it dry until it’s a firm leather hard. I often lightly texture the surface to add interest to the design (9).

Decoration

Once the piece reaches a dry leather-hard state, cover the entire piece with terra sigillata in whatever color appeals to you for a background (10). At this point, I occasionally roll a pony roller over some screening (found at the hardware store), that is pressed into the surface to add extra texture (11). Let the surface dry until you can touch it without making a mark.

Now use a sharp tool, such as a needle tool, to start drawing your initial designs. My favorite mark-making tool is a sewing needle held in a mechanical pencil—a tip I learned from Kari Radasch (12). Draw through the terra sigillata to the dark clay below. This all comes down to individual taste: I like drawing abstract shapes that are suggested to me by the shape of the piece, but anything goes in what you might want to do. I usually draw abstract shapes, then fill them in with a different color (13), but my favorite part is making marks and lines. Once I have some basic shapes laid down (14), I just let my imagination go. The order of making these marks and adding color doesn’t matter. Sometimes I draw first and then color, sometimes the other way around. Note: The timing is important here though: If the piece is still too wet, the terra sigillata will take forever to dry before you can start making marks. If the piece becomes bone dry, it’s still possible to carve it, but I don’t like the feel of it as well and it makes a lot of dust. I don’t burnish my pieces as I fire too high for the burnishing to remain, but I like the softer, waxier look I get with using the terra sigillata as a base.

Brush away any burrs on the surface left behind by the sgraffito process with a soft brush. Allow the piece to slowly and completely dry out.

Bisque fire the piece to cone 04, then lightly sand the surface with a fine-grit wet/dry sandpaper. Be sure to wear a mask and work in a well-ventilated area while sanding.

Now, while wearing protective gloves, apply a copper carbonate wash with a brush over the surface, making sure to fill in all of the carved lines and markings (15). Then, wipe off the wash with a damp sponge (16). Fire the piece to cone 2.

Finally, wax with Amaco wax resist diluted 4 parts water to 1 part resist and buff with a soft cloth to obtain a soft glow.

Rebecca Zweibel is a primarily self-taught artist who began her clay work in Colorado, continued in the Washington, D.C. area, and currently works at the Morean Center for Clay in St. Petersburg, Florida. Her website is www.rrzceramics.com.