Building an armature

1A skeleton for clay

Wet clay is heavy and soft. A solid clay head 18 cm tall weighs about 3 kg, and without support the neck bends and the head slowly sags. Sculptors solve this with an armature: a strong inner skeleton that holds the clay up, just as your bones hold up your body. A good armature also fills the middle of the head, so you need less clay and the walls are not too thick.

2Key vocabulary

• Armature: the inner support of a sculpture: here a base board, an upright post and a wire cage.
• Core: the light filling round the wire cage, such as dried banana fibre or newspaper, which saves clay.
• Plastic clay: soft, damp clay that can be modelled easily.
• Leather-hard: clay that has dried enough to be firm but is still damp; it can be carved, cut and joined.
• Bone-dry: completely dry clay: pale, fragile and ready for firing.
• Firing: heating dry clay in a kiln or a carefully built fire until it turns hard and permanent. Fired clay is called terracotta, Italian for "baked earth".
• Wedging: kneading clay to push out air bubbles and make it the same all through.

3Getting and preparing clay

• Buy clay from a local potter or brickmaker, or dig it from a valley bottom with the landowner's permission. Many of Rwanda's wetlands are protected, so dig only where it is allowed.
• Test it: roll a coil as thick as a pencil and bend it into a ring. Good modelling clay bends without cracking badly.
• Clean it: dry the lumps, crush them, soak them in water until they fall apart, then pour the mix through a fine sieve or an old cloth to remove stones and roots. Spread the wet clay on a cloth or on dry bricks until it is soft but no longer sticky.
• Wedge it: knead the clay on a board like bread dough for several minutes, pushing and folding. Cut the lump in half with a wire: if you see holes, keep wedging. Air trapped in the clay can burst in a kiln.

4Two kinds of armature

• Permanent armature, for a head that will only be air-dried: the post, the wire cage and the core stay inside for ever.
• Removable core, for a head that will be fired: wood, wire and thick solid clay must not go into a kiln. Build the head over a post wrapped in several layers of newspaper and a ball of newspaper. When the clay is leather-hard, cut the head in half with a wire, remove the paper, hollow each half until the walls are about 1.5 to 2 cm thick, join the halves again by scoring and slip, and make a small air hole where it will not show, such as under the chin.

5Materials (all low cost)

• A base board: an offcut of plank about 25 cm square and 2 cm thick.
• A post: a piece of broom handle, bamboo or square timber about 20 cm long, cut to size, with nails or screws and a small wooden offcut for a brace.
• Soft binding wire from a hardware shop, and pliers.
• Dried banana fibre (from the dry outer layers of a banana stem) or newspaper, string or sisal twine, and masking tape.
• Wedged clay, kept in a tied plastic bag.

6Make it: an armature step by step

1. Fix the post upright in the middle of the board: nail or screw it from underneath and nail a small brace beside it. It must not wobble.
2. Cut the post to height. Its top must stop inside the head, at about eye level, and never reach the surface.
3. Make the cage. Bend a loop of wire into an egg shape smaller than the planned head and twist its ends tightly round the top of the post. Add a second loop crosswise.
4. Make the wire safe. Bend every cut end into a small closed loop with the pliers and wrap it with tape.
5. Build the core. Pack the cage with banana fibre or crumpled newspaper and bind it tightly with string. Clay grips fibre and string far better than smooth wire.
6. Check against the plan. The core must stay 2 to 3 cm inside the planned surface everywhere, especially at the face, where you will cut into the eye sockets.
7. Give the neck a grip. Wind string or fibre round the post where the neck will be.

Worked example: sizing the core and the post

Mugisha's planned head is 18 cm tall and 12 cm wide, with 2.5 cm of clay all round.

• Core height = 18 − 2 × 2.5 = 13 cm; core width = 12 − 2 × 2.5 = 7 cm.
• His clay neck will stand on the board and be 7 cm tall, so the chin is 7 cm above the board and the eye line 7 + 9 = 16 cm above it. He cuts the post to about 16 cm, so it ends at eye level, deep inside the core.

7Look closely

This 18th-century French engraving by Robert Bénard shows the iron armature built inside a large statue of a horse, to hold the figure up while it was made and cast in metal.

• A cage of iron bars follows the shape of the body, and separate bars run down inside each leg.
• Props from the ground hold up the heavy body and the raised legs while the work is soft.
• The faint outline of the finished horse shows that every bar stays inside the final surface: exactly the rule for your 2 to 3 cm of clay.

Practice