Illustration: STAMPERS.
Illustration: FLINT MILL.
The art of making vessels of earth is one of the oldest of all arts;
the “potter’s wheel” is frequently named in Scripture, and pottery is
found in all the remains of ancient nations. Earthenware is made from
a mixture of clay and powdered flints; the clay is freed from all its
coarser parts by being stirred with water and drawn off after the
gross matters have settled; the fluid is then allowed at leisure to
let fall the pure clay which was mixed with it, and is then fit for
use. The flints are made red-hot, and in that state thrown into cold
water, which makes them so brittle that they can be easily broken up
by the “stampers,” which are perpendicular pieces of iron made to
rise and fall with great force; the flints are then ground in a mill
to a powder, which is treated in the same way that the clay was. When
these two earths are mixed in proper proportions, and beaten together
while moist, they form a substance of the consistence of putty, a
lump of which is thrown into the centre of a piece of board turned by
means of a wheel and treadle; while turning round, it is moulded by
the hands into a rough outline of the vessel required, and afterwards
put aside to dry till it becomes of such hardness, that it can be
easily turned in a common lathe, and formed into the cup, jug or
whatever else it may be intended for. This is then baked in a “kiln”
or oven so contrived that it shall make it red-hot, and keep it so
for about two days. If it has to be ornamented with a design-such,
for instance, as the “willow pattern”--a number of prints on tissue
paper of the subject required are kept ready, and one of these is
stuck on to the vessel with the printed side next to the clay, and
rubbed smoothly on to it; after a little time the paper is washed off
with water, and the pattern is left on the vessel. The next process
is that of glazing; this is done by dipping the vessel into a mixture
generally made of ground flints and oxide of lead made into a thin
fluid with water; when the glazing is dry the vessel is once more
put into the kiln, and made red-hot, when the glazing-mixture on the
surface melts into a smooth glass. Different colours are given to
the pattern by mixing certain metallic substances with the ink used
in printing. The handles, spouts, and other projecting parts are
fixed on after turning, and before the ware is put into the kiln.
Many kinds of pottery are not turned at all, but made in a mould by
being squeezed forcibly into it; this is the case when the article
to be produced is octagonal, or possessed of any form not round, and
therefore not to be produced by turning, and when the surface has a
pattern or figures standing out in relief. Some of these are made by
filling shallow moulds with the clay, and, while moist, affixing them
to the surface, but the handles of common ware are made by forcing
some of the clay through a hole of the required form, so that it
comes out in long strips or ribands, which are cut up into lengths,
bent into the proper form, and stuck on to the ware, some softer clay
being smeared round the joint--the whole, when baked in the kiln,
becoming hard and strong.
Earthenware is often made to possess some color throughout, as drab,
yellow, brown, or black. These tints are produced by admixture of
different kinds of clay and oxides in various proportions, oxide
of iron generally giving a red or chocolate color, and oxide of
manganese a drab, brown, or black color, according to the proportion
used.
Figures, busts, and many other articles, both for ornament and
utility, are made of porcelain by casting, and are produced by
filling hollow casts of plaster of Paris with the materials for
porcelain, mixed with water to the consistence of cream--this is
called “slip,”--and when the hollow cast is filled the porous
plaster absorbs most of the moisture from the portion of liquid
“slip” next to it, so that, after a time, what remains fluid being
poured out, there is found a coating or lining of porcelain mixture
of considerable thickness adhering to the interior of the mould too
solid to be poured out; the whole is then set in a warm place to dry,
and as the porcelain shrinks as it dries, it separates itself from
the mould--which, being made of several pieces fastened together, is
taken apart without injuring the cast; after it has thoroughly dried
it is baked in a kiln or furnace. This is called “Biscuit porcelain.”