Mold Materials

jay ojay o
edited March 2021 in Sculpture
Hello, I have a cat sculpted out of natural clay, and was wondering what kind of molds would work best for creating silicone skins for animatronics? I've used plaster in the past, but for something so large, it seems a bit heavy and much. Plaster also destroys the sculpture usually, and we actually want to create two molds from the same sculpture. What options for mold making would work best for this application?
Post edited by jay o on


  • Hi Jay,

    Epoxy and fiberglass molds are a great alternative to plaster or stone-based molds.  Our lesson series on making a silicone mask covers this type of mold making process quite well:

  • Would I be able to do a fiberglass mold straight onto the clay sculpture, or would I need to make a brush on silicone mold and then reinforce the silicone mold with the fiberglass being a shell?
  • You can apply right to the sculpture, though depending on your clay you may need a release or barrier layer, like clear spray paint.

  • What kind of barrier would work best for applying fiberglass to air dry clay?
  • Usually a clear spray paint like krylon crystal clear.

  • What kind of mold release could I use with the sealed clay sculpture and fiberglass? Also do you have any recommendations on fiberglass mold making material?
  • A release like Smooth-On's Ease Release 200 would do the trick.  There are a lot of release agents you can pick from.   Once you know the type of resin you are using in your fiberglass you can look up compatible releases via the manufacturer. 

  • Ok, sounds good! Any fiberglass resin recommendations?
  • Personally, I go with Smooth-On since I've had consistent results with them and their team is always helpful with answering questions. Their EpoxAmite system is great.  But you can go with whatever works for you.  I use epoxy resins rather than polyester as well, but both work.

  • Was looking at Epoxamite, wasn't sure if it was for the use case that I was looking for. Will probably use the Epoxamite system. Where can I get fiberglass to combine with the EpoxAmite to make molds of sculptures?
  • There are a lot of online retailers like Amazon that offer fiberglass, and it can often be found locally at hardware stores like Home Depot and stores that cater to things like boat or automotive repair.

  • Thanks for all the help! By the way, since it seems like you are an admin, would you be able to delete the post marked as DELETE on my profile?
  • My pleasure.  And I'll hunt that post down and delete it for you.

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