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Does Plaster of Paris shrink? Answered

Does Plaster of Paris shrink as it dries? I would like to make a mask out of it but I don't wan't it to shrink and crack.
Gratias agimus tibi,



Best Answer 6 years ago

No, it doesn't shrink. That's why it is used for things like paster cast impressions by police departments, and molds for casting gold and silver jewelry, etc.

Well, it does shrink a bit - try doing thick sections.


Its been a long time since I studied this, but as I recall, basic plaster of paris, without additives, actually expands slightly as it is curing. In the neighborhood of 0.3% to 0.5 %, nominal, if memory is correct. I don't recall the figures, but thermal expansion and contraction is also relatively small.

True, buts it shrinks very slightly in storage, so that dental impressions can be problematic

It will do what you want - DO NOT totally encapsulate any body past in Plaster of Paris.

you may find making a mould with alginate works better than a direct plaster cast,

Plaster will not shrink as it dries, therefore, it can be used to create a court-admissible cast as well as a reference which can be used in an investigation.