Pottery clays and
ceramic clays, also called moist
clays, are virtually the
same; they are all made with a
water base and need to be fired
in a kiln to vitrification to
become permanent. The
primary types of clay bodies are
earthenware and stoneware
which
turn red, brown or white when
fired.
Clay used for
pottery is indigenous to only
certain regions of the world and
every manufacturer uses the same
base clay. United States clay
body formulas are generally a
mixture of several different
types of clay, derived primarily
from clays mined in Georgia,
Tennessee, Ohio. Small amounts
of darker clays that make up a
formula, such as Van Dyke Brown,
are found in New Mexico. Clay
mined in California has a gritty
coarse texture and therefore, is
not usually used in formulas.
Fine grolegg clays from
England are used for making
porcelain clay bodies.
The
earthenware clays generally
vitrify at a lower temperature
than the stoneware or porcelain
clays.
(Vitrification is the process
whereby a clay body is heated
until it becomes non-porous.)
Stoneware clays fire to a higher
temperature and is, therefore, a
harder material than
earthenware.
There are
types of firing: bisque firing
and glaze firing, both done in
kilns at temperatures ranging
from cone 014 to cone 10. Bisque firing is the initial of first firing of a dried piece of pottery or ceramic, also known as greenware, performed before glaze firing.
Glaze firing is the second
firing; glaze is a colored
liquid material that can be
matte, gloss, or speckled.
It is a silica that when heated
fuses together and forms a
glass-like coating.
Most of the
tools that are used for clay
modeling can be used for
ceramics and pottery, but there
are also
ceramic tools
specifically designed for
ceramics and pottery. They
include: loop tools.
sharpened steel tools used
during the trimming and footing
process; the needle tool
used to level the excess clay
from the top of a pot.
Fettling knives are great
for scraping, cutting and
removing dried clay from seams
and other areas. Toggle
clay cutters, a 36-inch wire
attached to a wooden handle at
both ends, is essential to cut
sections of clay in the wedging
process and for removing thrown
pots from the wheel. Other
essential ceramic tools are the
elephant ear sponge and
potter ribs.
Visit our online
ceramics store
to view our moist clays,
ceramic tools and accessories.
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