Tips and Tools: Bucket Bisque Mold Olivia Tani

Appears in the April 2024 issue of Ceramics Monthly.

Create a bisque mold using clay, a bucket, and a few brilliant tricks to control its contour. After firing, you’ll have a custom drop mold and the skills to make more. 

Versatile Tools 

The soft curve of a hemisphere is a versatile springboard for many projects. The method of draping a slab over another curved surface certainly works; however, it is limited to the shape of the prop being used. This is why I prefer making drop molds where I can control the curve, the size, and the height. 

For several reasons, bisque-fired clay molds are versatile tools in my studio. They absorb moisture quickly and are durable when used with sharp tools. They do not require a prop mold or mixed plaster, not to mention eliminating the possibility of getting plaster chips mixed in with clay. Bisque molds are also a safe surface on which to torch clay, protecting the work surface from the torch fire. They are durable, stack and store well, and I can make them in virtually any desired shape. They can be incorporated into handbuilding and wheel-throwing practices. When I handbuild, I use them directly on top of my work table and on my banding wheel. In the practice of wheel throwing, because this particular mold is built in the round, they function well as a tool when attached to the potter’s wheel. For example, I use these molds to make plates and bowls; I tool the foot into a soft slab draped over the mold as it spins. 

I invented this bisque-mold-making method simply using a bucket, a small hole, a rubber cork, and a potter’s wheel. By alternately opening and plugging the hole in the bucket, I control the amount of air trapped inside the bucket. With pressure applied from above, the unplugged hole allows the slab to sink lower into the bucket. With the hole plugged, air displacement is halted, the slab stops stretching downward, and the pressure I apply is directed to shaping the curve of the concave surface. To achieve a more refined shape to the convex side, once it is leather hard, I turn the mold over and trim it further, directly on the wheel. Alternatively, because of the volume of clay in your slab, further alterations can be made with a Surform or other sculpting tools to make angular alterations like corners or ridges. After bisque firing, I have a sturdy tool that will last many years in the studio. 

Preparing the Materials 

Begin by choosing a hard-plastic, sturdy, and straight-walled utility bucket. Anywhere from a two- to five-gallon bucket can sit on a wheel head, with room for clay wads to hold the bucket in place. Remove the metal handle. 

Next, drill a clean hole anywhere on the wall of the bucket. Make sure the soft rubber plug fits nicely and forms a leak-proof seal. In between the canvas, roll out a slab that is about 2 inches (5 cm) thick, and at least 3 inches (7.6 cm) greater than the circumference of the bucket. I find it best to use fresh clay out of the bag or pugged clay, so the consistency is even and very plastic. Use a needle tool to cut away any excess clay (1). 

Creating a Drop Mold 

Carefully lift the canvas to slide a large bat or flat wareboard underneath the slab and canvas, making sure the slab is fully supported and does not overhang the bat. Uncover the canvas covering the top of the slab and center the top of the bucket directly on the slab. 

With one hand pressing firmly downward on the bottom of the bucket and the other hand under the board, flip it all over (2). If needed, have someone help; it can be heavy and an awkward movement. This method keeps the slab flat and undisrupted, so it sits evenly on top of the bucket (3). Remove the board and the canvas, and then center and secure the bucket to the wheel head. 

With the bucket in place, lightly spray the slab with water to allow the ribs to glide easily across the surface without catching on dry spots. Starting with the rubber plug out, and at a comfortable, slow wheel speed, use a large-toothed metal rib to gently apply pressure, starting from the outside toward the middle, holding the rib at approximately a 45-degree angle (4). Be sure to stay in the confines of the bucket’s walls. 

As the slab slowly sinks, keep applying steady, consistent gentle pressure until it is as deep as desired. Use a dowel and ruler to measure the depression. This measurement reflects how tall the mold is on the other side. Keep in mind that the clay can only stretch so much, so it may take a few tries to test the clay’s plasticity limits. Then, plug the hole (5). 

Use a fine-toothed serrated metal rib to do the same process as before, gliding steadily across the radius of the depression. With the hole plugged, more pressure can be applied and the bucket will hold air, so the mold will retain its volume, and the pressure will affect the shape. Once the desired shape is achieved, use a smooth metal rib or a red rib to refine the skin of the clay to its finished state. This is the concave surface of the bisque mold. Level the parts that overhang the bucket; it is the base that makes steady contact with work surfaces when the convex surface of the mold is used. 

Use a needle tool to trim off excess clay, leaving at least 2 inches (5 cm) of slab extending from the bucket’s edge (6). Leave the mold in the bucket to dry to leather-hard trimming consistency. As the clay dries and shrinks it will release from the bucket wall. Be sure not to move forward prematurely; the clay should not bend as it is handled, which can cause it to warp later on. Using the same technique as before, place a bat on top of the mold, flip everything over, and remove the bucket. 

Place the mold on the wheel head and refine the shape by trimming (7). The clay might initially look stretched and rough, but because the slab is so thick, there is plenty of clay to trim away rough spots. Refine the convex surface further with a metal or red rubber rib. To soften the edges, make picking the mold up easier, and to avoid potential chipping, trim a 45-degree angle into the edges on the extended slab base (see 8). Let it dry slowly, then bisque fire the mold. Congratulations on your new custom-made bisque mold! 

the author Olivia Tani earned her BFA from the New York State College of Ceramics at Alfred University in 2017. Following graduation, she moved to Minneapolis, Minnesota, as a 2017–2018 Fogelberg Studio Fellowship resident artist at Northern Clay Center. Olivia continued her engagement in the Minnesota clay community and maintains a studio at Northern Clay Center. To learn more, www.oliviataniceramics.com.