Before describing in detail the moulding of the various sorts of vessels, the accidents which are associated with this process should be discussed. These may result from one of two causes, the presence of foreign matter in the paste or imperfect moulding.
If the clay has been carefully sifted, as it usually is, there should be very little foreign matter in the paste. It is, however, impossible to remove entirely all gravel or stones fragment. If gravel is allowed to remain, it will cause the vessel-walls to scale during firing because of the difference in the rates of expansion under heat of stone and paste. In order to prevent this, the potter while moulding is constantly on the lookout for these small particles, which may be discovered at any stage of the work. They are at once picked out of the vessel, even if it is all but finished. The irregular hollow formed is then filled with a small pellet of fresh paste and smoothed over. The women say that a bit of hard clay does not cause flaking as does a piece of gravel or a stone splinter. Another kind of foreign matter is an air-bubble, which if left in the vessel will cause the same form of accident, because of the difference in the rates of expansion of air and clay. In order to eliminate these small air-bubbles, the pat is pressed down hard upon the puki
PLATE 14
a
Levelling and smoothing the rim of a bowl after it has been scraped with the kajepe, or gourd spoon. The left hand serves to keep the piece turning and to support the plastic wall.
b
Use of the kajepe in shaping a vessel; the left hand supports the wall within, while the kajepe, held in the right hand, thins the top of the wall and gently presses it inward.
and the rolls are carefully pinched at every point about the vessel. A skillful potter is able to feel an air-bubble even if it is covered with a layer of clay: such a bubble is pricked and the resulting hollow is filled as before.