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Always
open your mold, to check the
inside for casting clues.
Viewing the mold open will offer
many answers as how to handle
the casting of an item.
This is our B704 Colander..
A mold designed to produce a
piece as close to one hand
thrown as possible. It has
a solid core, and a footed base.
Both of these need to be
addressed in your casting
procedure.
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First..
the Solid Cores. If the mold is
dry, the core needs to be
saturated with clean clear
water. We use a well
loaded Large wool sponge.
Pressing the water out, it runs
down the sides of the core.
It often takes 4 water loaded
sponges to prepare the core for
casting.
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Re-build
the mold.. making sure the key
fit is snug.
Some 3 part molds, have slide
keys. These slide keys must be
seat together well.
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Strap the mold
together. |
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We need to measure
the required thickness of our
casting. How thick should
the wall of clay be, to obtain a
perfect casting of this mold.
We want no hollows.. The
photo shows the bowl portion
above the foot where we must
obtain a solid.
This measure is slightly over
5/8 of an inch.
We have 2 walls drawing moisture
and forming thickness.
So.. our casting thickness at
the spare before dumping.. must
be at least one half of 5/8
inch.
Our casting thickness will be
slightly under 3/8 inch before
dumping.
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NOW
ABOUT THOSE HARD SPOTS..
that often show up on the face
of ware..
Shown is the area which will
actually be the front inside of
the clay bowl.. Normally.. a big
hard spot would occur, because
your slip would hit this area of
the plaster first...
Because we have moistened
the plaster core.. it
is easy using a soft goat hair
fan brush to Paint some slip
into the area where our first
slip splash will hit the mold.
The reason we are able
to paint with slip.. is this
area of the mold is wet so clay
layering will not occur.
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When you begin
casting from your pitcher, be
sure you direct your first slip
hit .. on the painted slip area.
RESULT: No hard spots
on the face of the greenware.
Does this work on Plates? You
bet
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Since we have
measured for casting thickness.
we must cut into the spare wall
to check our thickness before
dumping.
This is the 3/8 inch thickness
that is required. |
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Turn the mold over
to drain..
Watch for the slip to stop
running..
then turn the mold right side
up.
You will need the runback of
slip to assure the area where
the bowl seats at the foot is
solid..
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When your casting
is ready, trim the spare
A bent
tip fettling knife is
recommended for this mold.
Begin the de-molding by
sliding off one of the top
halves. Then the other..
The ware will be resting on the
core portion of the mold.
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The inside of
footed base... is solid.
The bottom rim is smooth to
the body. No rim overhang
results if you have made your
casting to the correct
thickness.
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Now it's time to
cut out the marked holes.
Plastic Drinking Straws have
several uses in the casting
room. Hole cutting is just one..
but a valuable one.
The holes are marked. Simply
press the straw into the clay
until you feel the plaster core.
Then make a small twist of the
straw and pull out. The
clay stays in the straw.
You can actually do this 2 to
3 times, as the clay moves up in
the straw.
Then a simple snip with a
scissors and you have a new
empty straw portion to begin
with again. What A Tool
and disposable.
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Once all your
holes have been cut, it's off to
the air compressor..
You will use the compressor
nozzle and work all around the
the seam line.
Our Compressor produces 60
pounds of psi.
This would be a standard
compressor sold at hardware
stores.. for painting and shop
stuff !
Then simply lift the ware from
the core. The original
moisture added to the core in
the beginning aids in making
removal so easy.
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Ware is then
placed on a dry wall scrap, and
there is one more step before
this piece goes off to the
drying shelf. |
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At the bottom
inside.. there are 4 more
drainage holes for our
colander..
They are not visible from the
outside.. as that was actually
the inside of the casting.
Using the straw cut out the 4
marked holes. |
| Solid
Core Molds produce superior
quality.. bowls ! Casting
an open rim top pour bowl mold,
often results in varying
thickness in each ware.
Not a Good Thing.. |
