Do I need to seal an unkilned clay original before putting silicone on it to make a mould?

Question

I have done it without sealing on a smal scale but now I'm doing something bigger. If I should what should I seal it with???

Answer 1

It is possible dependant upon scale of the work, try sealing it in a undiluted pva glue this will provide some protection against the odd knock however you must apply this when the clay has started to dry out not when wet and once you have sealed it you will not be able to fire it, putting a covering of any sealant upon an unfired medium will cause water retention in the clay when you come to fire it it will blow
i take it that you are going to make a plaster cast mold,then if you are i use a covering of dental mix its a kind of substance that dental techs use to make impressions for false teeth,it goes off pretty quick then apply the molding plaster over the top this gives you a colour change so when you come to seperate and remove the wet clay you can see were the plaster begins the clay starts
its never failed me yet. LF

Answer 2

A potter friend gave me some advise on this, he recommended using washing up liquid (thinned a little) to coat a item with, to act as the releasing agent. if the bust wasn't so big I would recommend making a mould from a re-meltable rubber compound. These release well naturally from plaster and clay, but have to be heated to quite a high temperature.

Answer 3

yes you need to seal it!
as you have not described what you are using it for i cannot say what to seal it in.
try fibreglass as it can be sanded and shaped

Answer 4

Why don't you fire it first?

Answer 5

no