The Jeffersonian. [volume] (Stroudsburg, Pa.) 1853-1911, 1858-11-25
NO. 10.
Clay and its Uses.

There are few substances more useful
than humble clay. 1t is employed to
construct our houses, in the form of bricks;
aud, under the names of china and stone
ware, it assumes the most varied and
beautiful con6gurations in vessels and ar
tlcles employed in every household
When We reflect Oh the varied uses of clay
1t becomes sn exalted material in our es-
timation, because it is indispensable to
the supply of so many wants. Yet al
though it has been employed 10 the arts
from time immemorial, it's composition
and qualities are not very generally
known. Clay is the product of several
kinds of rocks; its character being deter.
mined by that from which it is derived.
1t is generally found as sedimentary
deposit, having been disintegrated FROM
rocks by the action of water and the at
mospbere. Common blue clay is the pro-
duct Of slaty rocks, and is mixture Of
the oxyd of the metal aluminium and in
palpable silica or sand. 1t is the alumni
.ous oxyd which renders it unctuous and
plastic when moist, and capable, in that
state, of being nodded into any form.--
The common clay used in IN akiug bricks
contains little oxyd Of iron; this, when
burned. imparts to them their peculiar
rod color.
The manufacture of bricks in our
country is carried on very extensively, in
volving the investment of an immense
aggregate capital, and the employment of
many thousand operatives. Within the
past fifteen years, machines have super
seded band moulding in brick ID skiDg, in
large yards All articles made of elsJ,
when exposed to very high temperature,
such as burning in kiln. acquire the
hardness of the rocks of which their ma
terials once formed part. Clays which
contain an alkali and iron, readily fuse
at high temperature, whereas neither
alumnia nor silica fuse, when unmixed
with other substances. Burnt bricks are
simple cubes of clay submitted to press
ure in molds, and gradually dried, to G.
vsporate the moisture slowly; then they
are exposed to high heat In the burning
process. As clay shrinks greatly when
it is being dried and burned, articles made
Of it must be fired very carefully, or they
will break in pieces or become distorted
in form. For this reason, bricks, when
nodded, are first dried in the sun, before
they are burned; during wet weather,
therefore, this business cannot be carried
on in our country in :he common way.
Potter's clay for stone-ware contains
43'5 parts of silica; alumnfa, 81 >; lime,
0'35; iron, 1; water. ls. This clay is
infusible in porcelain kiln; it only in
durates in firing, The glazed face in
stone-ware is made By q fusible compost
tion put on the surface.
Kaolin or porcelain clays are genrally
found in beds or seams among granite
rocks, from which they have been disin-
tegrated. They Contain no iron-feld-
spar is their base. Most Of the stone
ware and fine porcelain which come into
our country from abroad are nanufactur-
ed in Staffordshire, England, where Sl0,-
900, 600 worth of articles are made an
nually, three fourths of which are expor!
to America. English pors
celain is cheaper, but it is inferior to the
French. As the gliding aud ornamentug
of china ware greatly enhance its value,
and, of course, increase the tariff dues on
it, much plain porcelain is now imported
into, and afterwards decorated in this
city.
Fire-clay is composed of alumnia and
silica; and bricks made of it are very re-
fractory. Those used for our household
stoves are exorbitant in price, and are
generally inferior in quality. as they are
liable to fuse in burning what is called
"red ash" anthracite coal, which contains
a little iron. A stove can be lined 10 a
more durable manner with potter's clay
than with brick, at one third the cost.
1t is applied by plaotering it on the met
al, and allowing it to dry slowly after
wards. This information may be useful
to many of our readers, who can readily
obtain such clay Scientific Amerlcan.