How to Make a Square Baking Dish and Fill it with Rhubarb Crisp Wheel Throwing a Squared-Off Casserole Dish Sumi von Dassow

In my neck of the woods, it’s almost rhubarb season! So I thought I would repost Sumi von Dassow’s article on how to make a baker for rhubarb crisp, from the Pottery Making Illustrated archive.

In this post, Sumi demonstrates how she makes her lovely square baking dishes (that are great for any type of baked casserole!). –Jennifer Peollot Harnetty, editor

By springtime my green thumb gets really itchy. I’ve gotten my seeds and maybe I’ve been able to dig beds. There will be nothing to harvest yet for weeks, but green things are starting to come up. One of the earliest edible plants to produce a usable crop is rhubarb, and by March we may even see it pushing little pink fists through the earth and unfurling crumpled leaves. Time to start thinking about making a baking dish for rhubarb pies and crisps! If you begin this project as soon as you see the rhubarb starting to emerge, you can have it fired and glazed in plenty of time to try ceramic artist Sarah Jaeger’s rhubarb crisp recipe.

Every cook needs a square or rectangular baking dish, which is perfect for lasagna and brownies since you can make square servings. Crisps and crumbles are scooped out of the dish with a spoon, so they don’t really need to be baked in a square dish, but it’s fun to make a square dish anyway. For this baking dish, you can use glazed porcelain, stoneware, or earthenware clay.

Throw and Alter the Ring

Make a squared baker out of two parts—a ring and a slab. Start with about two pounds of clay and throw a short, wide cylinder with no bottom.

Tip: You don’t need to be scrupulously careful about making sure this ring has no bottom. If you try too hard to pull all the clay across the bat, you could pull it completely off the bat!

The ring should be 2½ to 3 inches high, though exact height is not critical. When you’re done, use a needle tool to cut a groove ½ inch or so inside the base to separate it from the excess clay in the center of the bat (figure 1). This creates a foot inside the ring that will be used to join it to the slab that forms the bottom. If you want to aim for a specific size, say 8-inches square, you need to do a bit of math. To turn a circle into a square, start by figuring out the circumference of your circle. The formula for circumference is pi (3.14) x diameter—so a circle with a 10-inch diameter has a circumference of 31.4 inches. An 8-inch square, with four 8 inch walls, requires 32 inches total—pretty close to the circumference of a 10-inch circle. A typical stoneware clay shrinks 12½%, which is 1⁄8th the total. So an 8-inch fired pot is 12.5% smaller than the original. To find the original size, divide 8 by .875 to get 9.13.

Roll the Bottom

After you make your clay ring, set it aside to stiffen up while you make a slab. I like to throw my slab on the wheel using a couple pounds of clay—a table or a slab roller with work just as well. I roughly center the clay, then flatten it across the bat with the heel of my hand.

Once both the ring and the slab are dry enough to handle, lift the ring from the bat and shape it with your hands into a square or rectangle (figure 2). If you really want it exact, use a dividing web, but I do it by eye.

Place the reshaped ring on your slab and draw around the outside with a needle tool, remove it, and cut out the shape with a sharp blade. Doing this avoids marking the reshaped ring with your cutting tool. Besides, you need to score and slip both the top of the slab and the bottom of the ring to join them. Or even better, scrub both pieces with a toothbrush dipped in Magic Water, making sure to work up a good amount of slip. (Make Magic Water by mixing one gallon of water with 3 tablespoons sodium silicate and 1½ teaspoons of soda ash).

Assemble the Baker

Place the squared-off ring back on the slab and smooth the two pieces together by working the foot you left inside the ring into the slab (figure 3). Use fingers and a rib to smooth the two parts together on the outside.

It’s a good idea at this point to add some kind of handle; whether it is pulled, extruded, or cut from a slab is up to you. Handles will make it much easier to remove the baker from the oven. Allow the baker to fully dry, bisque fire it, fully cover it with food-safe glazes, and finally fire it to the recommended clay and glaze temperature.

Then, make some rhubarb crisp following the recipe above!

Sumi von Dassow is an artist, instructor, and frequent contributor to PMI. She lives in Golden, Colorado.

**First published in 2014.