John Rodgers on tue 25 jan 05
May, are you sure you have no undercuts in this mold??
How about your soap. What did you use? I usually recommend tincture of
green soap cut to 50-50 with water. Apply with a sponge, workin up a
lather. Then allow to dry, and brush to a sheen with a china bristle
brush. Repeat three times, and after the third time, drip a drop of
water on the surface ans see if it beads up as if on wax. Plaster model
to be molded should be dry before soaping. And then cast the new plaster
right after the model surface is soaped and dried adequately.
If the mold sticks to the model, completely submerge the entire thing -
the model and the mold toether - in a bucket of hot water, leaving the
top edge of the mold even with the surface of the water. After soaking
a few minutes, pull at the top edes of the mold in a separating
direction. Should separate. If not, then bump one side of the mold along
the edge in a direction as to drive that side from the other. Use a
rubber mallet.
If all else fails, get some thin hardwood wedges, and drive them in
along the seam. This is a last ditch effort, and will result in some
damage along the seam but will probably separate the pieces.
You might try also using compressed air blown down into the seam line.
Careful here however, the pieces may separate violently.
Good Luck,
John Rodgers
Chelsea, AL
May Luk wrote:
>Hi all;
>
>Today I made a hump mould out of a mushroom plaster mould. I put about 4
>layers of soft soap water mixture so that I had a smooth sheen [after it's
>dried] on the mould before I pour plaster over it. So far so good, but now I
>have a big hunk of plaster and I don't know how to seperate the 2 moulds. I
>saw this plaster demo 2 years ago in Aberyswyth, and I finally get to try
>out the method today. I think I remember the demonstrator said something
>about a vaccum thingie, I don't recall very clearly. I just thought, if I
>get the soap going as per demo, the mould would come out very easily.
>
>What do I do now? should I wait until the mould is dry, or should I try to
>knock it about tomorrow while it's still 'fresh' ?
>
>I hope I made myself clear, I'm a bit cloudy as I had a ten hour day at the
>studio.
>
>T.I.A.
>
>May
>London, UK
>
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May Luk on tue 25 jan 05
Hi all;
Today I made a hump mould out of a mushroom plaster mould. I put about 4
layers of soft soap water mixture so that I had a smooth sheen [after it's
dried] on the mould before I pour plaster over it. So far so good, but now I
have a big hunk of plaster and I don't know how to seperate the 2 moulds. I
saw this plaster demo 2 years ago in Aberyswyth, and I finally get to try
out the method today. I think I remember the demonstrator said something
about a vaccum thingie, I don't recall very clearly. I just thought, if I
get the soap going as per demo, the mould would come out very easily.
What do I do now? should I wait until the mould is dry, or should I try to
knock it about tomorrow while it's still 'fresh' ?
I hope I made myself clear, I'm a bit cloudy as I had a ten hour day at the
studio.
T.I.A.
May
London, UK
Kathy Forer on wed 26 jan 05
On Jan 25, 2005, at 6:01 PM, May Luk wrote:
> What do I do now? should I wait until the mould is dry, or should I
> try to
> knock it about tomorrow while it's still 'fresh' ?
Let it set until the heat has been released and the plaster is cool.
Cut or scrape the "parting" line so it's nice and clean, with no
locking plaster overlaps. Then you can use a soft rubber or light wood
mallet to very gently tap around the edge, just slightly, to get a
sense of the leveraging points of the mold. You can then go around the
mold tapping wooden wedges (screwdriver or chisel) into the part. The
mold should start to come loose and you can remove it from the model,
using even prying and pulling pressure all around.
It can be helpful to cast a mold with small clay keys that you can
later remove, using the negative key as a place to tap a wooden wedge.
Compressed air works well to break a suction seal but is less necessary
with plaster than with rubber, though helpful. If you're really stuck,
try soaking the mold in warm water, then tapping a wedge around the
edge
Kathy
Locust, NJ
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