6 thoughts on “Mouldmaking and casting

  1. Hello David,
    Could you tell me if it is possible to use an epoxy resin object as a master when moulding with addition cure RTV silicone? Any advice on this would be gratefully received. Many Thanks and great site! Lynne

      • Yes it’s annoying. I understand if you happen to have addition cure silicone, you want to use it .. but I think it’s only worth it if it’s for specialised properties i.e. some are very fast curing, some like Platsil Gel good for prosthetics etc. For regular mouldmaking condensation cures silicones are much less complicated. I believe one should never automatically believe what one’s told though. I have this ‘no’ list from somewhere else .. can’t remember .. but I haven’t tested myself. Who knows .. if you can do a small test, with a thin Vaseline coating on the prototype .. maybe it will work.

    • Yes, it sounds like ‘polymer modified plaster’ would be what you’re looking for. Look in ‘Polymer-modified plaster’ in the ‘Materials’ /- ‘Casting’ section. Although it’s strongest using harder casting plasters it will make regular ‘plaster of Paris’ more waterproof too.

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