This post is not about the materials that go into the making
of glass, but about ways of forming glass once melted or dripped into a space.
Formers are a bit different from moulds. They are more like the formers used in
concrete structures – they are there to resist the movement of the contained
materials and give the form or shape desired rather than a natural flow.
These formers can be of anything that can resist the firing
temperatures of the process. Some of the
materials are stainless steel, ceramics, fibre board and paper, vermiculite, kiln
brick, and I am sure there are others.
Refractory Fibre
Most of these require a separator between themselves and the
glass. The ones which do not are
untreated refractory fibre board and fibre paper.
Most paper is not sufficiently strong to stand on its own.
Instead it is used flat and the shape cut out of it. It can be made in several layers and pinned
together to achieve the height desired.
It should be lined in the interior with a thin fibre paper to avoid
seeing the layers of the former in the edge of the glass.
For thicker work, fibre board can be used with the shape or
form cut from it. Alternatively, it can be used on its side backed up by kiln
brick or other material to resist movement. More information on methods and safety are here.
If hardened, refractory board and paper will need separators
between glass and former, just as most other materials will.
Sometimes the fibre board and fibre paper are not heavy
enough to resist the flow of the glass. You
can use weights to help resist the movement.
At other times, the glass flows under the fibre and then you need
something heavier. Fortunately, there
are a number of refractory materials that can be used.
Other common formers
Vermiculite board is another refractory material that can be
cut and shaped much like fibre board.
The vermiculite needs to be covered with kiln wash where it might come
into contact with glass or be lined with fibre paper or another separator.
Calcium silicate board can be used in much the same
way. It also needs a separator but does
not stand up to such high temperatures as vermiculite.
Ceramics,
especially in the form of cut up kiln shelves can be used as straight
formers. They have the advantage, over
refractory fibre paper and boards, vermiculite and calcium silicate, of being
heavy. They can resist the movement of
thick glass. They need to have a separator and usually a 3mm fibre paper, cut
3mm shorter than the final thickness of the piece, will provide the cushion in
the movement that the glass needs.
Kiln brick is an
often forgotten former. The bricks can
be cut and formed in many ways, even if not so freely as fibre board and
paper. The bricks do need fibre paper
separators to keep the glass from getting into the pores of the brick.
Stainless steel is
a common former too. These are usually
formed into an already determined shape and so are not so adaptable as many of
the other formers. Steel contracts much
more than glass and needs a cushion of fibre paper, usually 3mm thick to avoid
sticking to the glass.
More information on most of these formers can be found here.
