Some pieces the thrower shapes over a plaster-of-Paris
mould; and some he shapes inside the mould, reversing the process and
pressing the clay against its confining surface. The danger in thrown
ware comes from an uneven pressure on the clay resulting in a lack of
solidity; the pieces are not always equally firm at all points and in
consequence sometimes crack."
"Can pieces of any design be thrown?" inquired Theo.
"No, only round pieces such as cups, mugs, vases, jars, or bowls. In
other words, only circular pieces. Frequently, too, these are only
started by the throwing process and are finished by some other means
such as turning, for example."
"What is turning?" asked Theo.
"Surely you have seen a turning-lathe, Theo," asserted
Mr. Marwood. "Here is a turner just opposite us. You will notice he
has a lathe that goes by steam. The vase on which he is working has
previously been roughly formed on a jigger--a revolving mould over
which a sheet of clay has been pressed and quickly shaped. After such
a piece has been dried to a leather hardness the turner takes it in
its crude and uncompleted state and by running his lathe over it
planes down the surface to a smooth, even thickness.
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