Prepare your materials. Use smooth clay for fine details or clay mixed with grog. Grog is fired clay, finely ground into granules, that prevents shrinkage and provides stability during kiln firing. Grog-added clay works best for portraits requiring less detail. Use an armature to support the clay (see the tips section for advice on building a simple armature).
Gather your tools. Some common tools used in sculpting are the riffler rasp, which helps shape and form details; a wood modeling tool, which is useful for adding, subtracting and forming shapes in the clay; the serrated wire loop and the wood block are used to slice away portions of clay and even out textures; a caliper is a measurement tool used to gauge proportions; cutting wire and ribbon tools trim away portions of clay; and a wire brush removes dried clay from the other tools.
Set up your work station. Sculptor Peter Rubino recommends using a C-clamp to affix the armature between you and the live model, if you are using one. A model lets you capture the nuances of the face from all angles, rather than working from a flat photograph. Your results will be more lifelike. Place the clay on the armature.
Begin shaping the clay using the cutting wire and wood block. Try to keep the shape symmetrical, and form into a shape that approximates a head. Develop the basic shape first, and add details later. Rubino recommends keeping the subject and clay at eye level while working.
Keep clay moist while working by spritzing it with water when needed. Do not overmoisten, but lightly spray the surface, especially if you need to leave the work for more than half an hour. Place a plastic bag over the clay to keep it from drying out too much while you are away.
Begin sculpting one feature at a time, keeping an eye on the symmetry. Measure your model and clay with calipers as needed, comparing the results. If your portrait is only half of the actual life size, for example, allow for the appropriate reduction in measurement when using the calipers. Refer to the resources at the end of this article for specific guidelines on shaping facial features.
Form the basic shapes for the hair, but do not add hair detail until after the head has been hollowed out and the pieces reassembled.
Once you are satisfied with the portrait and consider it finished, hollow out the head so that it fires faster in the kiln and is lighter. Hollowing out the head also reduces the likelihood that air bubbles trapped inside the clay will fracture or blow apart during firing.
Stand behind the portrait. Position the cutting wire with handles 2 to 3 inches behind the front plane of the sculpture. Carefully avoiding the armature, pull the wire down until it reaches about 2 inches above the ears, then bring it back toward you until it slices completely through the clay.
Using a wood tool or palette knife, score the cut edges at intervals on the exterior before removing the head piece; these are registration marks which will help you align the pieces for reassembly. Remove the head piece and set aside.
Score an approximate circle with a tool in the head's interior. Leave about 2 inches around the outside of the circle.
Use a ribbon tool to scoop out the clay within the circle. The extra pieces can be moistened and placed in a plastic bag.
Use a cake tester or similar tool to poke small holes in the inside of the head. These will allow steam to escape if the piece will be kiln fired.
To encourage bonding, score the cut edges and use a paintbrush to wet them before reattaching the head piece. Repair and smooth the seam so that it is no longer visible, then add hair details.
After kiln firing or air drying (the process you use depends on the type of clay), add patinas and glazes as desired.