Some Hints on Throwing Porcelain
the many types of clay, porcelain is the finest -- and the most
difficult to 'throw' (form on a potters wheel). Porcelain, an 'artificial'
clay, is certainly no matrial for the beginning potter, who would
be much better off starting with a more robust clay like stoneware
But there are a few points that can be taken into consideration
when throwing porcelain. Porcelain is fairly 'short', i.e. it does
not have much plasticity. As it does not have much plastic strength,
it also tends to 'flop' easily, especially when too much water has
been used, or it is 'overworked'. So it is a good idea to use as
little water as possible when throwing porcelain.
Don't throw porcelain with water; use a porcelain slurry, which
will give the necessary lubrication with less water content.
If a piece, let's say a bowl form, is overworkrd, it will tend
to flop, i.e. it's walls will collapse. Once this has happened,
one might as well start afresh. However cutting the clay off the
wheelhead and rekneading it will not always suffice. To regenerate
the clay, kneading, letting it rest overnight and then rekneading
again is usually a good way to go.
If a piece looks like it might be getting a bit 'floppy', try working
it lightly with a gas burner, an electric paint stripper or even
a hairdryer set to 'hot'. This will dry out the clay enough to give
it another go. Of course the wheel should be turning while you do
this, to ensure an even distribution of the heat.
Generally it will be easier to throw thick-walled pieces than
thin-walled ones, but with practice wall thicknesses of about that
of a one cent coin or even thinner are possible. This will also
depend on the scale of a work -- the larger the piece, the thicker
the walls will have to be (to support the weight above).
Thin walls are not only achieved by throwing, but even more so by
turning (cutting off further layers of 'leatherhard' clay with special
Another common problem with throwing porcelain is cracking, which
can occur during the drying process, or during firing.
Never let throwing water accumulate in the base of your vessel.
Cut a piece of sponge and tie it to the end of a chop stick or something
similar. Use this tool to remove any excess throwing water or slurry
from the base of your pots.
Cracking is usually caused by uneven compression of the clay (I
will not delve into the issue of drying here). Some clays such as
raku or coarse earthenwares can be relatively forgiving in this
respect, but not porcelain. Uneven compression can result from water
accumulating in the base (see Tip 4). More often than not, it is
a problem with compressing the clay during centering.
Center your porcelain on the wheelhead; cut off with a cutting wire;
turn around (bash it back onto the wheel upside down) and recenter.
This method of centering will ensure that your clay is as compressed
on the bottom as it is on the top.
Another problem may happen after throwing the best piece, but
then it collapses as you are trying to get it off the wheel. That
can be pretty frustrating after putting so much effort into getting
it so perfect!
To ensure your work doesn't collapse when removing it from the wheel,
dry it out a bit (evenly and carefully!) with a small burner attached
to a portable gas bottle. In fact, with a bit of practice, you can
do this to such a fine degree, that you can turn the work immediately
on the spot, without first removing it from the wheel.
While these hints are not comprehensive, I hope that they will
help one or the other person with their porcelain throwing technique.
However theory alone will never be enough -- in this case the old
adage "practice makes perfect" certainly does apply!