Overview of Ceramic Methods from
Start to Finish
Molds
Molds are made out of plaster. To make a ceramic item, one pours
liquid mud, otherwise known as slip into the mold. Plaster has an
affinity for water, so it absorbs water out of the slip leaving a
thin layer of clay taking the shape of the mold. Slip is kept in the
mold for anywhere between five and thirty minutes, depending on the
size of the mold. It is then poured out and the mold is allowed to
drain. In anywhere between 30 minutes and a full day, the slip
remains in the mold until it hardens up enough to be able to stand
on its own when taken out of the mold. This is called the leather
hard stage.
Greenware
Once the item is taken out of the mold, it is called
greenware. Attachments like separate arms or legs are attached (slipped
on -using slip as glue) at this time. Also cut-outs, such as
windows in buildings or stars in lampshades are made. Any other
similar adjustments to the greenware are made at this time. The
greenware is then allowed to dry further until most of the water has
evaporated out of the piece. It is important to note that greenware
is extremely fragile from the time it comes out of the mold until
after it fires in a kiln. Remember that it is only air-hardened mud.
Preparation for Firing
To prepare the piece for firing, it is cleaned. Cleaning
involves using a small knife-like tool to remove the seam lines
where the two parts of the mold came together making a line on the
greenware. It is important to remove all traces of this seam line or
it will remain visible for the life of the piece. Further cleaning
can be accomplished by a scrubber file. More details can be added
with various tools to add back fur to an animal along the seam line
or to put initials in the greenware to identify the person preparing
it. Fine tuning of the original cuttings or attachments can also be
done at this time, making the piece as perfect as possible before
firing.
Firing
The greenware, after it has been cleaned, is put into a kiln and
the temperature brought up to around 2000oF. It takes
about 3 hours to get to this temperature. Once the kiln shuts off
after reaching this temperature, the piece is allowed to cool for
about 17 hours in the kiln. This slow cool down keeps the piece from
cracking which would happen if it were taken out sooner.
Bisque
When the piece as come out of the kiln, it is now called Bisque.
The piece is now less fragile and can be handled without so much
worry of it breaking. It will still break if you drop it, but it
won't disintegrate in your hands if you clutch it too hard as would
the greenware. The bisque can now be either painted with acrylics or
glazed, depending on the end product characteristics desired.
Painting
Bisque may be painted with acryllics, and if done right, will
look more realistic if drybrushed. Drybrushing and wetbrushing
are techniques that are best learned in a ceramics class.
Wetbrushing
is applying a brush loaded with paint to the ceramic piece.
Drybrushing
is a technique where the painter wants the details of the molded
item to stand out, such as fur on a wolf. First, the piece is
wetbrushed one color such as black or walnut. Then the color of the
fur or other detail is added by putting some paint on the brush and
wiping off most of it on an old towel. The paint is then brushed
across the grain of the piece, leaving the black in the crevices and
the color of the fur standing out. Other colors are applied also
across the grain, blending highlights, such as white or yellow, with
the original fur color. After the piece is done, it is sprayed with
either a matte or gloss sealer to protect the paint from rubbing
off. The piece is not fired again (It would burn off all the paint
applied.)
There are other textures that can
be added to a piece that is painted, such as glitter or rough
textures that look like rock.
Glazing
A piece may be glazed in order to make it water tight and give
it a glossy appearance. Glaze is, in actuality, glass. If a piece is
to have separately colored places on it such as designs or writing,
these separate colors can be applied either in the greenware or
bisque stage.
In the greenware stage one uses a
special clay-based paint called underglaze. When the piece is
then fired to bisque, the clay-based paint also hardens to bisque. A
clear glaze is then put over the bisque and the piece is fired
again.
In the bisque stage, to apply
multiple colors, one uses an underglaze for bisque. Depending
on the type of underglaze, another coat of clear glaze may/may not
be applied. The piece is then fired again.
If only one color of glaze is
desired, one would brush on this color of glaze. Various effects can
be achieved such a peacock look by using crystal glazes. A
piece can be made to look old by using a crackle glaze.
Glazing should also be learned in
a ceramics class. The correct amount to apply and how to apply it
are techniques that need to be learned.
Gold and Mother of Pearl
Gold and Mother of Pearl are called overglazes. These are
applied over a finished glazed piece. The gold application is
genuine 24K gold. Mother of Pearl is a mixture of chemicals that
make give the appearance of albalone or mother of pearl. Both of
these overglazes have to be applied on top of glaze and fired in a
kiln at about 1000oF.
If one wants to apply either of
these to a piece that is only partially glazed and otherwise to be
painted, the bisque must be glazed in the spots where the overglaze
will be applied, fired, then the overglaze applied on top of the
glaze, fired again, and then the piece may be painted.
Information extracted from
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Indiana Ceramic Supply, Inc. |
