Recently I’ve turned my attention from traditional, functional forms to forms specific for use in the microwave—an appliance often used by many time-strapped people. Most bakeware can be used in a microwave oven, but most microwaves are much smaller than a conventional oven, and they do cook differently, so I’ve begun to research forms specifically designed for use in the microwave.
One of these forms is the microwave popcorn bowl. By now everyone knows that microwave popcorn, the kind that comes in paper packets, can be damaging to your health due to compounds that volatilize as the package is heated. In addition, of course, the excess packaging makes this product expensive and wasteful compared to simply buying the kernels. The ceramic microwave popcorn bowl makes it easy to buy popcorn in bulk and make a healthful treat.
This popcorn bowl has a well at the foot in which oil and corn kernels are placed, and a lid with holes in it to allow steam to escape while keeping the popped corn from escaping.
To make ware for microwave use, you must make sure your clay is fully vitrified at the firing temperature you use. This means that the fired clay is not porous. If the clay is porous, when you use it in the microwave, the moisture that has absorbed into the body of the pot heats up along with the moisture in the food you are heating, and the pot may become unbearably hot to touch. This may not happen the first time you use the pot, if it has recently come out of the kiln. But after you have used the pot a few times, and washed it a few times, it will have absorbed moisture, and when you touch it to remove it from the microwave you could burn yourself.
To make the bottom bowl form, center 3 pounds of clay, and open it up, leaving only ¼ inch for the floor. In general you don’t need a trimmed foot on ware for the microwave, since a foot only adds height to a pot and this form needs to be less than 7 inches tall to fit in a small microwave. Make the floor about 3 inches in diameter before you start bringing up the walls. Since you want to leave a well in the bottom of the bowl, bring the wall up about ½ inch, then start guiding the clay out into a bowl shape (1). The challenge is to create this form without leaving a lot of excess clay at the foot. Tip: Work fast to avoid over-saturating the wall of the pot or it may collapse around the narrow foot. Once you feel you can’t bring any more clay up from the base, use a rib to widen and refine the curve of the bowl. Now use a small rib to stretch out the top half inch of the wall to create a gallery for the lid to sit on (2). As you push out on the rim with the rib, use the fingers of your other hand to support the wall below the pressure point, so you don’t simply flare the rim. Measure across the widest point of the ledge you have just created with calipers (3). Make sure the bowl isn’t more than about 4 inches high or 10 inches wide.
The lid is thrown upside down. Center the 2-pound piece of clay and make a mound about 5 inches wide. Open it up and throw a wide shallow bowl with a rim that matches the caliper measurement (4).
Fitting, Trimming, and Adding a Knob Handle
Once both pieces are leather hard, place the lid in the bottom bowl’s gallery to check for fit. The bottom bowl should need minimal trimming, just a bit around the foot to clean it up. I like to leave it slightly flared so I can grip it by the foot to dip in a glaze bucket.
The lid will need more trimming. Trim the outside into a smooth curve to match the inside, then throw a knob. Place a dry sponge (or two) under the lid to keep it from collapsing from the pressure as you attach the knob (5). If necessary, put a pad of clay under the sponge to raise it high enough. Center the lid right-side up on top of the sponge and hold it in place with wads of clay. Score and slip the center of the lid. Place a small cone of clay on the circle of slip, work it on with a fingertip, and then throw it into a wide shallow knob (see 8).
To make handles, pull a wide strap at least 8–10 inches long, allow it to dry slightly, and then cut it into two equal pieces about 4 inches in length. Curve the pieces into semi-circles and push the ends of each semi-circle down with a fingertip (6). Turn the bowl upside down and make two marks opposite each other just below the gallery on the outside. Attach the handles securely with magic water or clay slip (7).
Creating Steam Holes
You can simply put steam holes in the lid randomly, but it’s more fun to make a pattern. Center the lid on a decorating disk and divide it into sections with a needle tool (8). I like to make six sections.
Remove the decorating disk and center the lid on the wheel so you can draw a top, bottom, and middle circle, thus creating a grid of twelve boxes. Now, use the needle tool to create a pattern within the grid. Once you have a pattern you like, use a drill bit to put holes along some of the lines (9). Don’t use too small of a bit or the holes may clog with glaze—a 3⁄16– or ¼-inch bit is fine. Erase the grid lines with a damp sponge and use a countersink to bevel the edge of each hole inside and out (10). Allow it to fully dry, then bisque fire it.
Finishing and Glazing
To glaze these bowls, you must wax both the gallery where the lid will rest as well as the edge of the lid. If you try to fire the lid separately from the bowl, they may not fit together after the firing, and the lid may slip off a glazed gallery when you take the bowl of popcorn out of the microwave. Dip each piece in glaze, then dip a second glaze on the rim of the bowl and the top of the lid around the knob. Use a hole-cleaning tool (this tool has a little pipe-cleaner on each end) to scrub the glaze out of each hole (11), then touch up the glaze around each hole as needed. Place the lid on the bowl and fire it to full vitrification.
To make popcorn, place about a quarter cup of popcorn kernels into the well, and microwave on high for 2–3 minutes. Listen for the pops, and when the time between pops gets to 2 seconds or more, take it out of the microwave. If you try to keep it going until every kernel pops, you’ll get burnt popcorn. You can add a tablespoon of oil, melted butter, or coconut oil before popping, but it will take another minute or 90 seconds to pop. A lot of steam is generated by the popping corn, which may make the bowl very hot, so have pot holders handy to remove the bowl from the microwave.
Sumi von Dassow is an artist, instructor, and regular contributor to Pottery Making Illustrated. She lives in Golden, Colorado. Check out Sumi’s book, In the Potter’s Kitchen, available in the Ceramic Arts Daily Shop, https://ceramicartsnetwork.org/bookstorwe/in-the-potters-kitchen.