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Jabba84

Newbie Question re: plaster

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Hello, this is my first post so apologies if my question is greener than Robin Hoods long Johns! :D

I have created a plaster (Crystacl-r) mould, originally cast from a newplast (oil based clay like plasticine) sculpt I made. 

The aim is to paint thickened silicone into it to make some animatronic skin for a creature I'm creating.

Anyway, I am having a right old time cleaning the plasticine out of the plaster mould. I've tried casting a layer of  latex to pull the bits out, using a hair dryer to attempt to melt the plasticine, using wooden tools to try to scrape it out (which ends up scarring the plaster :angry:) all to no avail.

I read somewhere that you can use water and detergent on the mould, but as it is basically a plaster of Paris will this not get absorbed into and ultimately wreck the mould?

Can anyone suggest an effective method of cleaning plasticine out of crystacl-r plaster mould, that will not damage the details on the plaster at all?

All suggestions welcome... Many thanks in advance! :)

J

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Welcome to the forums, J. No need to apologize for your question. we've all been there at one point in our lives...

I think one of the great things about plaster is that the hardening of the material is a chemical reaction, not a "drying" function. The plaster will absorb moisture without breaking down and dissolving. You should be able to soak the mould which, in turn, will help with the release of the plasticine which is not absorbent. After the mould is wet, you might try using sharp pointed tools like dental picks to pull out the plasticine. Marks made by the picks should be minor and relatively easy to repair.

JohnnyK

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The guy that taught me plaster casting encouraged us to clean out our molds with acetone if we had used something other than mold soap as a release, so I think if you go gently and test it before hand you could try chemical methods.  

A rough Google search tells me that either Vaseline or mineral spirits will dissolve plasticine. Maybe try one of those?

 

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Thanks for the helpful replies guys!

Tonight I will soak the plaster mould in some luke warm water with a bit of mild detergent, then use some (plastic) kids modelling tools to try to get it out.

Any remaining plasticine and I'll  use some mineral spirits, which happily I have lying around, to finish the job off.

All your advice is much appreciated!

:)

cheers,

J

 

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