TURNING OR SHAVING
"A sharp spear needs no polish."--Zulu proverb.
The turning or shaving operation takes place when the green shape has
dried to a _leathery_ condition. It consists in shaving the sides and
hollowing the base until the thickness is uniform. The shape is thus made
much lighter and rendered less liable to crack from unequal contraction.
At the same time a fine finish is imparted to the surface.
One of the handiest tools for shaving is shown in Fig. 27, no. 6, but a
piece of hoop iron bent at right angles and shaped with a file will serve.
Small hollows can be finished with a modelling tool. An old piece of
leather will close up and finish the surface. In factories a horizontal
lathe is usually employed, the shape being fitted over a _chum_ or
_chuck_. Skilled men can turn shapes down until they are scarcely thicker
than tin, but this, it is needless to add, is an abuse of method even with
porcelain, and quite out of place with stoneware or earthenware. All that
is necessary is to trim the thick sides, hollow the base, and smooth the
surface. (Fig. 35.)
[Illustration: FIG. 35--SECTION SHEWING TURNED & THROWN WALL OF A
SHAPE.]
A simple way to arrive at this is to throw on the wheel a chuck of stiff
clay to fit the shape, wide-mouthed ones being fitted over and ordinary
shapes within the chuck. (Figs. 36 and 37.) A piece of soft linen is
placed over this chuck to prevent sticking and the shape fitted and
centred. When spinning quite truly from right to left and steadied with
the left hand, the tool should be gently applied as shown in the
illustration. Hollow the base and then shave the sides, turning all down
very gradually and improve the outline as much as possible in the process.
[Illustration: FIG. 36--SHAVING THE BASE.]
[Illustration: FIG. 37--SHAVING THE SIDES.]
Care must be taken with the base. If it is not quite true it should be
sandpapered to stand flat. A little experience will soon show when it is
in the best state for shaving. If the clay is too soft, the tool jumps,
forming ridges, or possibly cuts deeply into the form. If it is too dry,
the surface crumbles and the pot is liable to break. When turned in the
right leathery condition, the shavings curl off like peel from an apple
and all tool marks are easily removed. A beautiful finish may then be
imparted with the leather.
To end the process the shape is reversed in the chuck. Those most
important parts, the shoulders and lip, are carefully rounded with a piece
of felt and polished with the leather. Properly attended to, this will
save much work and disappointment later on. Then with all holes filled up,
all ridges, bumps, and sharp edges removed, the shape is signed and put to
dry.
For very delicate work in transparent glaze or under-glaze painting, the
whole surface may be gone over with very fine sandpaper and polished with
the hand. This may be done provided the body is a fine one, for with a
coarse body this is apt to leave the surface looking gritty. Some little
practice will be necessary in throwing stiff chucks and centring the shape
securely, but this once mastered, the method here described will be found
to be expeditious and satisfactory for turning shapes.
A proper regard for process points to the desirability of leaving built
shapes without a high finish.
Yet they also, if built carefully and stoutly, may be turned down in the
above manner. The building up and turning down is somewhat tedious, but it
is sometimes the only way by which a craftsman can obtain large shapes. A
rather more simple process is to centre the shape upon a whirler and turn
down with a sharp wire tool, finishing off lightly with a sponge and soft
leather.
To accomplish this satisfactorily the shape must be fairly soft, as there
can be no quick spinning motion to enable the tool to cut cleanly as in
the chuck or the wheel. When the head of the whirler is of plaster, it
should be well soaked in water and the centred shape stuck down with soft
clay. The hand holding the cutting wire tool must be held steady at a
fixed distance from the centred shape and the pot may be sprayed with
water blown through a diffuser from time to time, to keep it moist. Some
clays will not, however, stand much re-wetting.
[Illustration: FIG. 38--POSITION OF TOOLS WHEN SHAVING.]
It should not be necessary to caution the craftsman against angular
profiles, splayed feet, or sharp mouldings. Such features are foreign to
good pottery, however suited to metal or stone.
With taste and judgement the irregular grooving caused by the tool can be
made of high decorative value. In no case should the built shape try to
masquerade as a thrown shape. When the whirler is used to shave down built
shapes, they may be coiled very thick at the base, thus allowing more
rapid work.
The attention must then be concentrated on the profile of the inside. In
this way many shapes that splay out or curve boldly from the foot may be
built, which would otherwise present many difficulties in coiling.