slows on sun 3 dec 00
I read from an article that, a glass artist put a glass bottle into a =
plaster mold and put them in a kiln to fire.........
For those of you who also deal with glass, what kind of plaster is that? =
Is that the same plaster we use for casting? And what is the tempeture =
the glass melt?
Thanks
W.S.
Bobbruch1@AOL.COM on mon 4 dec 00
<<<<bottle into a plaster mold and put them in a kiln to fire......... For those
of you who also deal with glass, what kind of plaster is that? Is that the
same plaster we use for casting? And what is the temperature the glass melted.
Cast glass is fired in molds that contain a high degree of flint. The plaster
is fired along with its contents and the mold is lost in the process.
Not sure of the temperature, but I think I remember that it is somewhat lower
than mid temperature clay and perhaps fired for a lower period of time.
Most of the cast glass firing that I have seen has not been with solid
objects like a bottle, but with granular glass to control color and
consistency throughout the form.
Marianne Bornet on wed 6 dec 00
I did glass at college, not ceramics which is a recent departure for me. To
answer your question about what plaster is used, I remember that we were not
allowed to used the ceramics plaster for our kiln molds because it was a much
better quality and more expensive. We used to add flint to strengthen our
molds and I also reinforced them with chicken wire because they sometimes
split under the weight of the molten glass. We all used to regularly pinch
the ceramic plaster because they kept telling us it was much denser, the art
was of course in not getting caught! I used to make glass pieces using the
lost wax technique and fired and soaked at about 900C (recommended temp 850C
- another not getting caught situation). Above this temp the molds start to
weaken seriously and fall apart. The temp at which you fire the glass is
dependent on what you are trying to achieve - slumping, fusing or casting and
what type of glass you are using - bottle glass, window glass, crystal, etc.
But remember, the tricky bit with glass forming is the annealing cycle.
I can try to be more specific if you'd like to give me more details or you
could try your local library or book shop for a great book called "Techniques
of Kiln-formed Glass" by Keith Cummings.
Regards
Marianne ( in the South of France where its been raining on and off since
October - not on! )
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