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Hi Brian,
Brent & I have been looking at this off site
recently.
I spent a lot of time looking for an unpolemerized
methyl methacrylate with a catalyst.
wich is the raw materials they start with to make
the sheets. Eventually I found some
with a plastics guy who has blown domes
for me.
He bought a drum of it & said it was very hard
to work with. With the domes there is a very controlled heating
process
in pressurized ovens. Out gassing in the setting
process forms bubbles that attach to the sides of the molds
and are hard to remove. Hugh went over to
Stanley plastics & saw the process. He said they over
compensate
the dimentions to allow for the outer faces to be
taken back beyond the " bubble layer ".
I've mucked around with polyester casting resin for
a while & large castings are a bit of an art. They can take days to
set,
& there is a relationship between temperature
& amount of catalyst. If you get it wrong the mold cracks or the materials
too soft.
Hope someone else comments, it would be interesting
to learn more.
Alan
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