I don’t think any of the parting agents normally used will work with
an RTV mold because the liquid will wash away the film layer a
separation mold depends on. One way to do it is to pour and cure 1/2
of the mold, then apply the parting agent, and then pour and cure the
other half. This take a relatively long time – two cure cycles-- but
it will work. The parting agent you use depends on the RTV rubber you
choose. Silicone sprays should not be used with RTV silicones because
they can act as bonding agents - -the wrong idea entirely! We
(CASTALDO) make an non-silicone RTV called LiquaCast that is cheaper,
stronger, longer lasting and easier to work with The separation
agent for this compound is any kind of wax - Pledge furniture polish,
or any other kind of spray wax.
If you (or any one else out there) would like a free sample of
LiquaCast, please let me know and please give me your shipping address
(no P. O. boxes, please).