Building clay onto the armature: score and slip

1Joins that last

Press two pieces of soft clay together and they seem to stick. But as the model dries, each piece shrinks and pulls away from the other, and a few days later the stalk lies on the table or a crack runs round the neck. Clay has no glue of its own. Potters and sculptors everywhere solve this in the same way: they roughen both surfaces and add liquid clay, so that the particles of the two pieces lock together. In this lesson you will cover your armature with clay and join every piece so that the still life dries as one solid sculpture.

2Key vocabulary

• Score: to scratch criss-cross lines into a clay surface before joining it.
• Slip: clay mixed with water to a thick cream, used as a joining liquid.
• Blend: to smooth clay across a join until no line shows.
• Slab: a flat sheet of clay of even thickness.
• Coil: a rope of clay rolled between your hands and the table.
• Pellet: a small flattened piece of clay, about the size of a coin.

3Make your slip

Drop a few small, dry lumps of the same clay as your model into a jar, cover them with water and leave them overnight. Stir to a thick cream, like porridge. Use the same clay, because different clays shrink by different amounts, and a join made with the wrong clay can still split.

4Joining in four steps

1. Score both surfaces that will touch, with criss-cross lines about 2 mm deep. Use a fork, a needle tool or an old toothbrush.
2. Slip: brush slip onto both scored areas.
3. Press the pieces together firmly with a slight twist, until slip squeezes out of the edge.
4. Blend: with a modelling tool or your thumb, drag clay from one piece across the seam onto the other, all the way round, then smooth. If you can still see a line, the join is not finished.

An old toothbrush dipped in slip scores and slips at the same time, which saves time on small joins.

5Three ways to cover an armature

• Slab wrap, for large smooth forms such as the body of a gourd. Lay clay between two sticks 1 cm thick and roll a bottle along the sticks. Drape the slab over the core, press it close so that no air is trapped, cut away the extra folds, and score, slip and blend the seams.
• Pellets, for uneven forms such as roots and stones. Press flattened pellets onto the core one at a time, each overlapping the last like the scales of a fish, and smooth each one into its neighbour.
• Coils, for necks, stalks and rims. Wind a coil round the wire in a spiral and blend each round down into the one below.

6Make it: cover your still life

1. Gourd body: wrap the paper core in a slab 1 cm thick. Trim and join the seams, then smooth the body into the shape of your drawing.
2. Neck: score and slip the top of the body, then build the neck with coils up the wire until the loop is just covered. Blend every coil and the joint with the body.
3. Avocados: cover each small core with a slab. Where an avocado touches the gourd or the board, score and slip both surfaces and join them, so that the group becomes one piece.
4. Leaf: roll a slab a little thinner, about 7 mm. Cut out the leaf with the needle tool round a paper template. Lay the leaf wire on it along the midrib, cover the wire with a thin coil, and score, slip and blend. Lift the leaf onto its paper former and join its stalk end to the group.
5. Check the thickness all over (see the first worked example).
6. Between lessons, mist the work lightly with water, cover it with a damp cloth and tie a plastic bag loosely over it.

Worked example 1: checking the thickness

Mutesi pushes her needle tool straight into the gourd until it touches the paper core. She pinches the needle at the clay surface with her fingers, pulls it out and measures from the tip to her fingers: 1.0 cm on the sides, but only 0.4 cm on top. The top is too thin; it could crack or show the paper. She scores the area, adds slip and a pellet of clay, blends it in and tests again: 1.0 cm. Finally she smooths over the tiny needle holes with a fingertip.

Worked example 2: why did the stalk fall off?

On Monday, Niyonzima's mango had a fine stalk. On Friday, the stalk lay beside it. Two clues explain why. The end of the stalk is smooth and clean, so it was pressed on without scoring or slip. And the stalk was a thin, solid coil, which dried and shrank faster than the fat mango. He scores and slips both surfaces, presses the stalk on, blends clay down from the stalk onto the fruit, keeps the stalk short, and wraps it in a strip of damp cloth for the first two days of drying so that it dries at the same speed as the fruit.

Practice