Found Collection

Is plaster of Paris OK to use for a glass molding material (e.g. slumping
base.)  Are there any special temperatures to be aware of etc??

Any hints also please?

--
SImon Hogg

No, plaster of paris by itself should not be a good material for slumping
molds.
 Most often a mixture of plaster and silica flour (available at pottery
supply
places) is used 50:50.  When the water is driven out of plaster of paris,
it
crumbles to dust.  
  Potters clay also makes nice mold forms, normally only fired just above
the
use temperature.  Slip cast white clay can also be used.
  Mike Firth

Simon,

I use a 50-50 mix of Hydrocal (plaster) and 200 mesh silica flour (brand
name I use is Silco-sil).  Works well for casting, although there are
better (and more expensive) materials.

Cheers,
Rick
Rick Sherbert Glen Echo, Md.

I have tried using plaster  many times and I find that I need to soak very
often as the plaster casts tend to be very massive ( more so than clay)  I
have never gotten more than a few slumps out of plaster and it is general,
more trouble than its worth unless I have a one shot to do.  Now I tend to
resort to the formable fiber mat, its just a whole lot easier.
   Right now I am experimenting with some different types of clays to do
molds,  Raku clay is said to have a high resistance to thermal shock and I
think that is the best one so far.

--

The Wood & Glass Co. 608-284-6200
Custom Stained Glass, Supply, & Lessons

: >Is plaster of Paris OK to use for a glass molding material (e.g. slumping
: >base.)  Are there any special temperatures to be aware of etc??
: >
: >Any hints also please?
: >
: >--
: >SImon Hogg
: >

: From what I have been told you really want a higher temperature mold
: material.  PoP may not last over too many firings.  Most pottery supply
: houses should be able to help you (or e-mail me and when I get home I
: will look up the compositions of the better high-temp mold materials).

: Rodger

--
i can add to your discussion a bit, as i have done PoP molds with glass...
the material is fine, but  you need to add silica (i hope i remember that co
rrectly) in order to  keep it togehter under higher temps.  plaster is great, very flexible...

good luck
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                   gregory j yanito
        graduate research assistant  
              kent state university                    
             school of architecture