throw - to form a ceramic vessel or other object on the potter's
wheel. Throwing is not always a straightforward thing. It certainly
is not something that is learnt in a few minutes. The finer the
clay, the harder it is to work with. Sometimes a plaster bat can
be useful when throwing these finer clays. Then, it is possible
to remove a precarious piece from the wheel head without actually
cutting it off -- it just stays on the bat and the bat is removed,
freshly thrown vessel and all.
Here is a simple method for casting plaster bats.
The first thing to do is to find a cake tin that has the same
size as your wheel head. Next, find a surface that is totally even
and level. This is important, because if you do not work on a level
surface, your bat will wobble on the wheel. So you will have to
get hold of a water level/guage, to make sure that the table or
whatever it is you are working on is 100% level. Now you are ready
to mix the plaster. Use about 1 1/2 -- 2 pints (750 -- 1000 ml)
of water and mix with plaster according to the instructions on the
plaster bag. This should result in a liquid level in your cake tin
of about 1 inch (2.5 cm).
After a few hours, or better after letting stand overnight, remove
the bat from the tin. If you have screws in your wheel head for
wooden bats, you may want to install the same for your plaster bat.
Caution! The plaster is brittle. Drill the holes slightly larger
than you will require for your pins, and insert a piece of thin
plastic or rubber tube (as would be used with an airbrush). This
tube will protect the bat and make sure it lasts much longer than
if you used the raw plaster for the hole.
Place the bat on the wheel and trim the edges with a trimming
tool. Now you can also wipe over these edges quite vigorously with
a wet sponge, to furhter soften them. This will help to ensure no
rough edges will chip off easily. Let the bat dry for a few days,
but be aware that the bat may need some rewetting before throwing,
otherwise the clay might not stick at all.
And remember -- plaster and clay do not mix, so be careful not
to get plaster chips in your clay. These can cause small holes and
other irregularities in the fired work!