Bryan,
I am going to cast 30 superstructure wondows for my 1/72 Prinz Eugen.
As they will be a 1 off I will use plasticine hardened in the freezer overnight as long as the small amounts wont get too warm.
Bob
I have used plasticene a few times...quite successfully...but as you say, they are for "one-off" mouldings. If you build to a regular scale then a lot of the fittings are going to be "standard".
For my actual mouldings I tend to use "dental" acrylic...the sort of stuff that my palate is made from. Comes in 2 parts. One is a pink powder that is finer than talc, and the liquid part smells good enough to keep you off the "wacky-baccy" for ever! But when mixed and poured into a mould and allowed to set (just a few minutes) it dries as hard as iron. Not cheap, but for those making multiple castings it probably would work out cheaper and better than the overpriced material that modellers are charged.
Brings me back to the moulding material.
A mould needs to be flexible and reasonably long lasting. "Proper" silicone moulding material seems to have a very short shelf-life and becomes impossibly expensive. Has anyone out there used Silicon-Sealant as a moulding material? It seems to have a lot of the properties needed. Must experiment! BY.