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Object Stuck In Usg-1 Plaster....help Please!

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I took a 1 inch circumference doll rod and drilled a 3/4 inch circumference cone shape into it about 3/4 of an inch deep.  I put a spray finish on it, sanded it down until super smooth, then put greensoap (3 coats) on it and made a one piece mold of it.  it is roughly 6 inches long.  I can not get the doll rod out of the plaster.  I'm thinking it may be a suction issue.  I poured the mold about 20 hours ago.  I slapped it with a shoe.  I drilled a hole in the doll rod (the 1/2 inch sticking out of the mold), and put a screw in it and tried to pull it out with about 150 lbs of pressure, and it wont budge.  Does anyone have any suggestions?  Thanks in advance.





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I assume by your description its a cone shape thats smooth with no under cuts.

its not suction its pressure and expansion most likely. Plaster gets really hot and moist as its goes off.

I suggest air pressure when the mold and wood are dry.

I am guessing that the wood may have expanded as the water and heat in plaster as its goes off tends to stick forms even when they are super smooth.

wood especially can do this.

when the mold dries (in a week or two) it may come out easier if its water expansion

the best way to deal with wood is seal it real well before casting it even with that its often tough

and as your mold is 1 piece its can be extra hard.

6  inches of taper on a 1 inch wood rod is not that much really  considering the depth.

I would let the mold dry and see what happens in a few weeks

Next time consider a two piece mold or seal the wood better.

This may take some tme to dry out.


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I had a really good book from the library that gave good advice for such issues.   It's not this one, http://www.amazon.co.uk/Lovers-Guide-Making-Molds-Ceramics/dp/1579901867/ref=sr_1_1?s=books&ie=UTF8&qid=1398963941&sr=1-1&keywords=clay+lovers+guide but was like this but much more detailed.  But I can't find it again grrrr.


Some of the things I remember are to soak the mould in water or to tap (hit firmly) the mould with a rubber mallet so the mould moves in the opposite direction to the model........


Good Luck, been there too...

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If the wood wasn't sealed, even with mold soap the plaster can really stick to it. Like Mark said, give it time to totally dry and see if it releases then. You may be in a situation where it won't come out cleanly, though.

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