Preparation
Many ceramic plant pot saucers can be used as circular
moulds. Most are unglazed and will
accept kiln wash easily. Some are
unglazed, but polished to such an extent they are no longer porous. These and glazed flower pot saucers need some
preparation before applying kiln wash.
Plant pot with saucer |
Polished and glazed saucers require roughing to provide a
key for the kiln wash solution to settle into.
This can be done with normal wood working sand papers. You may want to wear a dust mask during this
process, but not a lot of dust is created.
You could also use wet and dry sandpaper or diamond handpads with some
water to reduce the dust further.
If the sanding of the surface does not allow the kiln
wash to adhere to the saucer, you can heat it.
Soak it at about 125C for 15 minutes before removing it from the kiln to
get the heat distributed throughout the ceramic body. One advantage to the ceramic is that it holds
the heat, because of its mass, for longer than steel. Apply kiln wash with a brush or spray it onto
the warm saucer. As it dries, apply
another layer of kiln wash. Two or three
applications should be enough to completely cover the surface. If not, then you probably will need to heat
up again before repeating the process.
Alternatives
to plant pot saucers
There are alternatives to the saucer approach to getting
thick circles from a pot melt.
Fibre
paper
You can cut a circle from fibre paper and melt into
that. The advantage of fibre paper is
that it requires little preparation other than cutting and fixing. You may have only 3mm fibre paper and want a
9mm thick disc. Simply fix the required
number of layers together with the circle cut from each square. The fixing can be as simple as sewing pins,
copper wire, or high temperature wire.
Then place some kiln furniture on top of the surrounding fibre paper to
keep it in place on the shelf during the melt.
This furniture can often be the supports for the melt.
Fibre
board
If you find cutting multiple circles of the same size a
nuisance, you can use fibre board.
Simply cut the circle from the board with a craft knife. You will probably want to line the circle
with fibre paper, as the cut edge of fibre board can be rough. Alternatively, you can lightly sand the
edge. Wear a dust mask and do this
outside, if possible, to keep the irritating fibres away from the studio. If
you want a thicker melt than one layer of board can give, just add another
in the same way as for fibre paper.
In both these cases, you may wish to put down a layer of
1mm fibre paper to ensure the glass does not stick to the shelf and does not
require sandblasting.
The advantage of the fibre paper or board alternative to
flower pot saucers is that you do not need to kiln wash anything unless you
want to. If you do not harden the fibre paper or board, it will not stick to
the glass.
Vermiculite
board
Another alternative is vermiculite board. The advantage of this is that it comes in 25
and 50 mm thicknesses, so you can make the melt as thick as you like without
having to add layers. You can cut the
vermiculite board with wood working tools.
Knives will not be strong enough to cut through the vermiculite board.
You will need to kiln wash or line the vermiculite with fibre paper, as the
board will stick to the glass without a separator.
Damless
circles
Of course, if you want a circle without concern over the
thickness, you can do the melt without any dams. You need to ensure that the
shelf is level. Any supports for the pot
will need to be both kiln washed and far away enough that the moving glass does
not touch the supports and distort the circle.
In general, one kilogramme of glass will give a 300mm circle, so your
supports need to be further apart than the calculated diameter of the
circle. An undammed circle will vary
from 6mm at the edge to as much as 12mm at the centre, depending on
temperatures and lengths of soaks.
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