How do you make a casting of plaster of paris with a foam core? I've tried ...

How do you make a casting of plaster of paris with a foam core? I've tried and the foam floats up to the top... do you just wait for the plaster to harden and then put it in? is there an anchoring technique or some tool or clip?

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1 week ago #2
MICHAEL
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if you are casting a hollow plaster shell and want to add the foam so it remains light weight then yes you would let the plaster dry then pore in your foam. if you where just making foam heads then you would make a silicone mould apply release agent after it cures. then pore the foam so it would be a foam head with the face details on it.there are three foams medium. soft. and rigid. not really sure why people want to do that though as there are cheaper way's to do the same thing.

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1 week ago #3
iego
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what I am casting is not hollow... and the plaster sculpture may be too heavy to hang on the wall. So I was wondering if I pour the plaster into my mold, then add some styrofoam, and then cover all that with more plaster-- how do I keep the styrofoam down so it doesn't become visible?

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1 week ago #4
MICHAEL
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HI IEGO. i make hollow plaster castings like skulls in a mould i use two or three coats of plaster using a good quality stone plaster with water based polymer to give it durability when this sets in the mould i flip it over then ad plywood with cling film on it i pore more plaster in the mould first then when i flip it the plaster runs down and coats my plywood. this gives the appearance of a solid casting when removed from the mould and the result is a light weight casting and you would not think it was hollow to look at it. you could add your foam then paint the plaster onto your foam to hide the foam. plaster can be painted on polystyrene or foam.cut and sand some of the foam that you think will stick out before adding the plaster. hope i'm understanding you right and i make sense. if you can flip your mould over then put a large piece of ply on it and weight it down you can cut a pore hole in the ply if you want and pore the foam through it so you will know if it is all covered when the foam rises up to the pore hole. then just sand that part of.

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