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42761Re: Need advice

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  • abascirocco
    Apr 11, 2013
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      FWIW, US Gypsum also has a plaster specifically formulated for non-ferrous metal casting, they call it simply USG metal casting plaster. The other major North American plaster manufacturer is Georgia Pacific, they also have a line of metal casting plasters.



      --- In hobbicast@yahoogroups.com, Dan Brewer <danqualman@...> wrote:
      >
      > So here is a link to one supplier.
      > http://www.sheffield-pottery.com/U-S-Gypsum-1-CASTING-PLASTER-50-lbs-p/rmcaspla50.htm
      > The name of the company is US gypsum not US plaster. Brain fart. The way
      > that I use it is to take my wax master with sprus and vent attached and
      > coat it in Jet dry. Yes the stuff you use in your dish washer. It breaks
      > the surface tension on the wax and allows the plaster to stick. I mix a
      > little of the plaster up to the consistency of thin pancake batter and
      > paint it on. until I have coated the entire master except the top of the
      > pouring cup and the top of the vents. . I let that dry a little miz a
      > little more up a little thicker and put on another coat. When still wet I
      > sprinkle flint sand on the entire piece. Let that dry for a little. Mix up
      > some more plaster about 60/40 plaster sand and coat the piece. Let dry. You
      > should have coated the piece about 1.4 to 1/2 inch thick by now. Mix up
      > some more plaster 50/50 sand and plaster. sprinkle each coat with sand. The
      > next coat should be 30/30/30 plaster /sand / and grog. Grog is previously
      > fired plaster that has been broken up in to pieces that will fit through a
      > #8 sieve. When you have 3/4 to one inch of plaster wrap the piece in small
      > chicken wire. This is to keep the mold from breaking up when you fire it.
      > Add another inch of plaster , grog, sand to the outside of the mold. The
      > top and bottom of the mold should be able to support the mold with out
      > tipping over. The top because when you fire it the top will be down so all
      > of the wax will leave the mold and the bottom so you can fill the now
      > vacated mold with metal. Let dry .for several days in a warm spot. I place
      > mine on a blotter board. My blotter board is a 2x2 piece of drywall.
      > Place in your kiln and heat at the rate of 100 deg f per hour until the
      > melting temp of the wax has been reached. My kiln has a stainless steel
      > sink in the bottom that is plumbed out the bottom to get some of the wax
      > out of the kiln. I am able to recover some of it but not much. after the
      > wax is out around 200 to 275 deg you can ramp up a little faster Fire at
      > 2000deg f for 4 to 20 hours depending on size of the piece. Let cool to
      > around 400 deg and pour.. Cover the pouring cup and vents with perlite or
      > vermiculite and let cool. When the outside of the mold is just hot enough
      > to touch sweep off the perlite/ vermiculite and you can remove the
      > plaster. Remember that it will be hot. I use a hammer and a water hose to
      > remove most of the plaster . Plaster will clog your drain . More clean up
      > can be done with a stiff brush or sand blasting.
      > For more information look up lost wax casting , ceramic shell casting.
      >
      > Dan in Auburn
      >
      > Other places to find casting plaster are pottery suppl houses. jewelery
      > supply houses. And there are lots of formulas of the casting plaster. This
      > is just the one that I have been using.
      >
      >
      > On Thu, Apr 11, 2013 at 11:56 AM, Inventor <welfab@...> wrote:
      >
      > > **
      > >
      > >
      > > Hey Dan,
      > > About a half a dozen links wouldn't hurt....
      > > A few to read up about it.
      > > A few more as to where to buy it for "20 BUCKS"
      > >
      > > All I've found was clay and that 'started' at $85/50#.
      > >
      > > Grandpa Bill
      > >
      > >
      > > --- In hobbicast@yahoogroups.com, Dan Brewer <danqualman@> wrote:
      > > >
      > > > On of the problems with using POP is that it is hygroscopic meaning that
      > > > the material will never release all of the water trapped in its
      > > structure.
      > > > It actually will draw water out of the atmosphere . I would use a
      > > material
      > > > that when fired will vitrify and change to a substance that now will
      > > reject
      > > > water. American plaster makes casting plaster. 50 lbs goes for about
      > > > 20USD . There are several others. Plaster of Paris is best left to the
      > > > art casting for statues.
      > > >
      > > > Dan in Auburn
      > >
      > >
      > >
      >
      >
      > [Non-text portions of this message have been removed]
      >
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