Hollowing a Ceramic Sculpture
My first figurative ceramic sculptures were made about 10 years ago. They were slowly and painfully created through a seemingly-endless process of correcting and re-correcting my mistakes. Thus it was especially heartbreaking when a sculpture exploded in the kiln — as a significant number of those early pieces did.
In the beginning, my sculptures were hollowed in one of two ways: either by splitting the entire sculpture down the middle and then reassembling it, or by hollowing as much as I could reach from the bottom. Both methods tended to leave inconsistencies in the thickness of the walls, which greatly increased the chances of a blowout in the firing process. These crude hollowing methods also placed stress on the clay walls during the hollowing process, which led to cracks and warping when the pieces were fired.
Over time, I developed a more precise method for hollowing my sculptures, which has shortened the drying time significantly, and also virtually eliminated instances of sculptures exploding in the firing process. With a bit of practice, it is also a time-saver — which is nice, because hollowing is one of my less-favorite parts of the sculpture process. Essentially, my technique involves making multiple access holes to hollow small portions of the sculpture at a time. This allows me to create very thin, even walls throughout the sculpture, without placing stress on the overall structure of the piece. A recent Guild volunteer, Cheri, was kind enough to photograph the process as I hollowed one of my recent goddess sculptures.
When the sculpture is leather-hard, I begin by identifying an area to hollow — in this case, the head — and place the access hole where it will cause the least damage to any fine details. A small clay knife or X-acto knife is ideal for making a clean cut. It’s important to angle the cut so that the two pieces will seat together neatly when reassembled. (Think of the lid on a jack-o-lantern.) Two small registration marks help to perfectly line up the pieces for reassembly.
(Sculpting my figures bald allows easy access at the crown of the skull for hollowing the head. Hair is added at the end of the hollowing process.)
A needle tool can be used to mark the thickness for the walls until you get a feel for the process. 3/8″ to 1/2″ is an ideal thickness for any sculpture under 18″ tall; larger pieces require slightly thicker walls.
Trimming tools in a variety of shapes and sizes are useful for hollowing as much of the sculpture as you can reach from each opening. Here I am using the fingers of my left hand to make sure the walls are of even thickness. Working slowly is the best way to prevent accidentally hollowing through the walls.
To prevent air from being trapped inside the head and creating pressure during firing, I use a needle tool to make small openings in the ears. Similar air holes can also be hidden in the mouth or in the texture of the hair.
Each piece is scored and slipped for reassembly.
The registration marks eliminate any guesswork as to how the pieces fit together.
I clean up the join line with an angled wooden tool. (This is by far my favorite sculpting tool for figurative work.)
I create as many access holes as necessary to hollow every portion of the figure. Cutting more smaller access holes is often preferable to avoid disrupting the overall structure of the piece. This sculpture required six openings: the head, one on the back of each shoulder, a large cut down the front of the torso (pictured above), and an opening on each hip/thigh.
Using my fingers to determine the thickness of the walls.
With the hollowing process now complete, the last access hole is ready for reassembly.
A needle tool is used to place several more air holes on the bottom of the sculpture.
All the clay that was removed during the hollowing of this sculpture.
The final stage in the hollowing process is the addition of hair. Here, the bald crown of the head is prepared by scoring and slipping, which helps the soft clay of the hair adhere to the leather-hard surface of the sculpture.
The hairstyle on this piece wasn’t part of my original design — but sometimes a spontaneous bit of whimsy is exactly the right thing to finish off a work of art.
I typically place a newly-hollowed sculpture under plastic for a day or two, which allows any excess moisture from the slip to even out before the piece is air-dried. This helps to minimize the possibility of hairline cracks opening up along the seams due to uneven moisture. In my experience, a sculpture hollowed with this method will be bone-dry and ready for bisque firing within two days of air drying in low humidity, or about a week in high humidity.