Techniques for sculpting a portrait in ceramic clay

Water based clay is a ceramic clay - literally soil and water. It originates as a soft, plastic clay that gets progressively firmer as the water begins to evaporate. You can work with water based clay over a long period of time as long as you carefully mist the surface of the clay and enclose it completely in a plastic bag to keep the moisture content high. 

There is a fine line, however, between well hydrated clay and a sloppy, slumping mess of mud. A clay that has too much water content will droop (or slump) under its own weight and can literally collapse or break into a pile. Additionally, if you mist too aggressively, you risk having the features and top surface of the clay "melt" and blur just as a wave will obliterate detail from a drawing mad in the sand on the seashore.

Sculpting portrait in clay demonstration ©Lori Kiplinger Pandy

Water based clay comes in many different varieties, colors, and firing temperatures and is usually purchased in 25 pound bags from distributors. In it's unfired state, water based clay is very fragile, however once fired, ceramic sculpture can last centuries - some of the oldest clay figure sculptures date to around 25,000 years ago.

When selecting a clay for sculpting there are a wide variety of choices and options. Clay can be completely smooth, such as CT3 or it can be heavily grogged (grog is a sand-like additive made from fired and crushed clay) such as Chestnut. Grog can make the clay very course and give a pebbly, scratchy surface, but it's very useful in making the clay stronger and shrink less during drying and firing.

Water-based clay is quite heavy and I can easily use 25-40 pounds of clay when sculpting a bust so it is important to have a sturdy armature and support for all that weight. When doing a portrait I start with a wood dowel or steel pipe for me armature. Then I bulk out a form using newspaper - this gives a larger surface area for the clay to rest on and takes up space. Then I lay on the clay and begin to build up the shapes and forms/

Sculpting portrait in clay demonstration ©Lori Kiplinger Pandy

It's important to mist the clay and cover with plastic between working sessions to keep the clay fresh. As the clay dries a bit, it firms up, allowing you to work the forms. When the sculpt is complete it is ready to dry out a bit - it needs to come to a leather hard stage to hold its shape before cutting and hollowing out the inside.

Sculpting portrait in clay demonstration ©Lori Kiplinger Pandy

Once the clay feels firm, it's time to cut it into pieces. A bust is very unlikely to fire as a solid piece, it must be hollowed. If fired while this thick, there is a strong likelihood that air bubbles or a bit of water will remain in the thick clay. Once the piece is fired in the kiln, the air will expand or the water will turn to steam and the sculpt will crack or even explode into pieces.

Sculpting portrait in clay demonstration ©Lori Kiplinger Pandy

Begin by cutting the piece with a wire into two or more pieces. Take a wire loop and carve out the interior clay. I try for an even thickness of 1/2" to 1" of clay wall. I also save the clay pieces and reuse them. It's easy to puncture or break the clay in this fragile state, but most things can still be repaired. Once the two sides are hollowed, it's time to score the edges, coat liberally with slip (a glue made with water, clay and a bit of Epsom salts) and mend the sculpture back together.

Sculpting portrait in clay demonstration ©Lori Kiplinger Pandy

Once the clay is back together, I carve out where the seam was, fill with fresh clay and rework the surface. Now it's time to carefully dry the sculpture. I start by covering with plastic and opening the plastic up a bit more each day to expose more of the sculpture to air. The drying process can take 2 weeks to 4 weeks and show be controlled to eliminate cracking. Once completely dry, the entire bust will be placed in an electric kiln and fired in ramped up phases for12 hours, then left to cool in the kiln for another 12 hours. Finally, I'll remove the fired ceramic sculpture and patina with 40-60 transparent glazes of color.

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