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BUILDING A PIECE OF POTTERY

1. Making the First Coil

2. Testing the Outline

3. Continuing the Piece

Should the walls become weak and insecure from working them too rapidly, let them dry for a longer time, several hours or over night, before finishing. Test the shape constantly with the cardboard outline. When the jar is as high as the drawing, or even a quarter to half an inch higher, let it dry over night. It should then be smoothed with an oval steel tool, which has a saw-toothed edge (see Fig. 5), to take the worst unevenness off. The tool is bent to fit the shape of the jar and held at right angles with it, smoothing it with short strokes in different directions. This is done inside and out. The hollows are also filled in. To do this, wet the spot first with slip and fill in with clay as nearly the consistency of that in the jar as possible. The sides are then made perfectly even with the oval tool with smooth edges, holding it as the saw-toothed tool was held. When there are no hollows or ridges and the walls are about a quarter of an inch thick, the surface of the jar is smoothed with a damp sponge and polished with the fingers and thumb inside and out, taking care in handling it not to hold it by the edge, but rest it in the hollowed hand. Should it have become very dry, as it will in a comparatively short time in warm weather, so that it is light-gray in colour, it will be wise to smooth it with sandpaper instead of with the sponge, as in this state even a little water may cause it to crack. One cannot learn too soon, or have too often impressed upon one’s mind, the risk of adding wet clay to a piece of pottery that is much drier. The natural shrinkage which has already taken place in the dry clay will be repeated in the wet, and, as it shrinks, it will crack the drier clay. Cracks in clay are of two kinds—those caused by shrinkage of the unbaked or green clay, and those that come from cooling too rapidly in the biscuit or baked clay. The former can usually be mended satisfactorily, but for the latter there is no remedy; the piece is spoiled.