Fractured Fabrication Wade F. MacDonald

Appears in the Sept/Oct 2022 issue of Pottery Making Illustrated.

At the beginning of my journey in ceramics, roughly 25 years ago, I honed my skills on the potter’s wheel with the aim to sustain myself creatively and financially as a production potter. Even early in my graduate studies, I pursued this idea, until my first formal critique. I quickly learned, from my mentor, Paul Kotula, the many nuances of successful pots and the rigor required to make them. As a result of that critique, I realized the limitation and naiveté of my goal and recognized a simultaneous expansion of my vision as an artist. Leaving pots behind for a time created room for intellectual and emotional development. When I returned to the vessel, my visual vocabulary had grown; I was a different person. 

So much has changed in the world of ceramics since I started my love affair with clay. I have come to understand that the field of ceramics is expansive and inclusive enough to embrace every approach to the material. Whether functional or sculptural, geometric abstraction or realism, purist or mixed media, digitally fabricated or sloppily crafted, each is relevant in shaping the future of our field. Pots are powerful objects. A potter imbues each vessel with their experience. In using handmade pots, we are allowed a glimpse of the maker’s life.

Influences

I am drawn to areas outside of the field of ceramics for inspiration. I look at and experience a lot of architecture and design. Many of my lifelong friends have become architects and designers or work closely with art and design objects. I’ve also been fortunate to have traveled to centers of art and design, experiencing both firsthand. Jorge Pardo continues to be a major influence, as well as Zaha Hadid. I felt the sublime power of architecture after walking through Daniel Libeskind’s Jewish Museum in Berlin, Germany. As a graduate student, I watched the entire construction of Zaha Hadid’s Broad Museum on the campus of Michigan State University. These influences surreptitiously find their way into all aspects of my studio practice. 

Modeling and Printing

When I begin vessel design, I start on the computer. I use Rhinoceros, a 3D-modeling software program. Rhino is quite sophisticated and has the capability to be very precise; however, I use it as a way to sketch or quickly plan projects. In Rhino, I typically start with polygon mesh primitives (a combination of the points or peaks, edges, and surfaces that define a three-dimensional object). Then, I select several mesh forms that I will overlap in the Rhino environment. I might start with a simple sphere. I continue to add forms until I reach the complexity desired. Finally, I have created three simple forms that I will combine into one cohesive piece. In order to merge these mesh forms, I perform a Boolean Union command. Once the Boolean Union is complete, there are several ways to alter the form. Twisting, stretching, or tapering are a few options. I reduce the number of mesh planes in the form until I reach something very abstract. This final form can be altered to resemble a vessel and scaled accordingly. The result is a finished rendering (1).  

Three-dimensional printing entails several steps. In Rhino, I save the file in .stl format and import that file into a program called Cura. Cura is used to prepare the model for the printer. Cura translates the model into slices. In Cura, I scale the model and add a 15% structural infill, which strengthens the final plastic print (2). A G-code (a code that tells the printer what to do) is generated in Cura and saved to an SD card. The 3D printer reads the file from the SD card. I use an older Creality CR10 printer, which is one of the cheapest printers on the market. It usually gets the job done, but it can be temperamental. This printer creates the form in a plastic material.

Making the Mold

First, attach the plastic positive to a piece of melamine using spray adhesive. Because the model is filled with air pockets, it could become buoyant in the plaster, so it is important to ensure that the form is adhered. Brush a generous amount of Murphy’s Oil Soap on the model and on the melamine surrounding the model. 

Next, use cottle boards as a barrier for the plaster. I find these give a finished look to the sides of the mold and are very easy to use. Add a pencil mark about 2 inches above the form as a reminder to not overfill the mold (3).

I do not use a formula when mixing plaster. I start by estimating the amount of cold water needed and add pottery plaster until the dry plaster begins to accumulate on the surface of the water. When enough plaster has been added, I wait for 5 minutes before mixing. I use a drill with a mixing blade attached to mix the plaster and then immediately pour the plaster into the mold. Pour the plaster slowly as to not introduce any unwanted air bubbles or loosen the mold (4).

By placing the mold on a table that is low and movable, you can shake the table gently to force the release of any air bubbles trapped in the plaster. Once the plaster hardens, heats up, and then begins to cool down, you can detach the cottle boards. Clean the mold with a large Surform and a scouring pad and flip it onto wood blocks to dry. 

When the mold is dry, draw lines where you want to cut the mold using a bandsaw (5). The cutting lines are determined by the shape of the mold, and are intended to eliminate undercuts that lock the model in the mold. Caution: Follow all safety procedures when using a bandsaw. Use a vent hood to gather dust. And, always wear a respirator, eye protection, and ear protection. 

Now, I make the first cut (6). If the plastic model can be removed at this point, I do not need to make a second cut. Because of the complexity of this form, the mold must be cut into four parts. After the mold is cut, remove the pieces of the plastic model and spray the mold with compressed air to remove plaster dust and plastic shavings. Gently clean the mold using a scouring pad and water. Soften the sharp edges and make any repairs to the mold, like filling holes left from air bubbles (7). Once the mold is totally clean and semi-dry, it is ready for casting.

Casting the Negative Mold

I use a casting slip that is 6-Tile kaolin based. Always mix your slip thoroughly and sieve it prior to filling the mold (8). Watch the level of the slip while it is drying and top it off if the level gets too low. Agitate the surface of the slip or mist it with water to reduce scumming.

Look for the slip walls to be almost ¼ inch thick before dumping the slip out. With the mold upside down and placed on wooden stilts, let the excess slip drip out. Using a soft rubber rib,  scrape the dried slip from the mold. Then, use the rib to remove the drips on the lip of the cup (9).

Cleanup and Handles

Because of the shape of this particular form, it is important to remove it from the mold before it reaches the leather-hard state. If it dries too much, it might tear along the tighter angles as the clay shrinks. I find that cleaning these forms works best when the piece is at the end of leather hard. In order to get an even lip and a clean bottom, gently rotate the cup around on wet canvas (10). Next, carve away the mold lines, sponge and smooth the surface, and address the lip and base. 

At this stage, either work on the handle for a mug or leave it as-is if it is to remain a cup. The hollow, tube-shaped handle is cast from a different mold. Once the handle is at end-stage leather hard, cut a section off of the open end at a 60° angle (11). Refine and smooth both cut ends on the wet canvas. 

Rotate the cut sections, score, add slip, and attach them together (12). Instead of slip, I use water. This cuts down on the mess. Add a small hole with a needle tool so air can pass out of the handle during drying and firing. Attach the handle to the cup and apply light pressure to ensure the handle is secure. Once the handle is attached to the cup, I add a short support that will be fired in place throughout the entire firing process (see 13). This ensures the weight of the handle will not warp the cup wall. 

Color and Glaze

When the piece comes out of a cone-08 bisque firing, do some simple cleanup, like sanding rough spots, especially around the handle attachment. Apply an underglaze color over the entire exterior of the piece and fire it again to cone 08 (13).

After the second firing, begin using stencils on the exterior. The stencil material is an adhesive tape used for drywall installation. Each face of the cup needs a custom cut stencil (14). This part can be very time consuming. Once all of the stencils are attached, spray the next layer of underglaze (15). When the second layer is dry, carefully peel the stencils away from the piece. The mug is now ready for a third bisque firing. 

After the third bisque firing, it is time for glaze (16). I always pour a liner glaze first. The exterior is sprayed with a cone-5 clear glaze (17). I program a 30-minute hold at the top of the firing cycle. This has helped with cloudy or bubbly clear glazes. When the piece has cooled, I wet sand the bottom. 

Wade F. MacDonald is assistant professor of art in ceramics in the Department of Art and Art History at The University of Alabama in Tuscaloosa. He holds an MFA from Michigan State University. Wade lives with his wife and stepdaughter in Birmingham.