Bill Merrill on sun 16 aug 09
Can't remember if I sent this out or not
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Jeremy
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For every 80 cubic inches of finished plaster you need ..(.example 8" x =3D
10" x 1" =3D3D 80 cubic inches )
1 quart of water and 2 3/4 pounds of plaster. If you want a harder =3D
denser plaster mix use 3 pounds of plaster for every quart of water. I =3D
use # 1 potters plaster.
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Put your water in your mixing bucket. Use lukewarm water. Cold water =3D
retards the setting time, hot water is not reccommended as there is no =3D
working time. Add the plaster by sifting the plaster into the water =3D
with your hand until the plaster is absorbed into the water. DO NOT =3D
STIR for several minutes. Give the plaster a chance to absorb the =3D
water. Stir the plaster by adjatating your hand undder the surface of =3D
the mix. The plaster will become throughly mixed this way. The =3D
stirring will start the mix to go through it's chemical change. Tap the =3D
bucket up and down to get rid of air bubbles, they will come to the =3D
surface. Drag your finger across the mix. If the mix peaks a little =3D
without settling down totally , this is a good time to pour. Pouring =3D
too thin will allow the plaster/water mix to potentially to run out of =3D
seams in your mold. Don't forget to put a mold release on the walls of =3D
your form so the plaster will release. If building a flat angled mold I =
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use Melamine, a product that has a formica like surface on one side. =3D
The plaster comes off easily.When the plaster starts going through the =3D
heating stage of setting up, wait a few minutes and release The screws, =3D
rubberbands whatever is holding the form together. Thyis will keep the =3D
pold from developing any cracks at joints due to expansion of plaster =3D
when going through the hardening stage. During the heat stage the =3D
plaster is weak and the mold shoul not be taken off for at least 20 =3D
minutes,
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Make a batch large enough to make 1 pour. I have several 30" by 30" x =3D
3" wedging areas.
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30" x 30" x 3" =3D3D 2700 2700 divided by 80 =3D3D33.75 quarts of water.=
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2.75 lbs plaster X 33.75 Qts ofwater + 92.8 pounds of plaster.
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If you have not poured plaster before this amount is not advise without =
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help. Make a 4" x 4" x 4" open cube. use mold release and figure your =
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plaster and water amounts. Pour the form. When the plaster use =3D
something like a metal straight edge to take off any extra paster. =3D20
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If making a wedging table, use Melamine so the bottom of the mold is =3D
perfectly smooth. =3D20
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Bill
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