Need recommendation on molding / casting products

Hey guys!

I would like some recommendation on the products I should use for molds and casting of bone props for a costume.
I've never done any molding or casting before, I would like to give it a shot, but there seems to be SO many products to chose from with Smooth-on and it's making me really confused haha

I want to make bones to use on a belt for my boyfriend's LARP costume, they are not going to be too big, but they need to be solid enough, lightweight and I want to paint on them as well (also wondering if it's better to use a primer before painting?).

My plan was to sculpt 2-3 different bones in Plastilina sulfur-free clay , make some molds and then make several bones for the belt. This is a drawing that my boyfriend made and he told me the belt on the main crow is similar to what we're aiming for here. I'm happy that he is trusting me with this project since this is my very first request for some prop since I started learning from Stan Winston courses here and I want to give it my best!

For paint, I was thinking of using Vallejo's acrylic primer and paint and I also have PEBEO acrylic paint and some watercolor pencils. I would have liked to use an airbrush but those are still slightly out of my budget at the moment...

So just to sum it up into a few questions:
What are the best materials from Smooth-on that I should use for the mold and the casts themselves?
Do I need to use a primer on the bones before painting them with acrylic?

Thanks for the help!


  • Options
    I understand your stress about picking the right materials.  There are so many out there to pick from for the molding and casting phases.

    One suggestion I would make since you mentioned this is for LARPing would be to cast the bones in something flexible like a polyfoam.  They'll be lighter, look just about the same, and will also be a bit safer.  When casting flexible parts you can use a rigid mold, which means you could make a simpler/cheaper mold out of a plaster/stone material like Ultracal or Hydrocal.  A foam like "FlexFoam-iT" from Smooth-On is a great option, and what I would probably go with.

    If you are casting a rigid resin bone you could mold with a tin cure silicone like Mold Max 30, or if you want to go with a similar platinum cure silicone there is Mold Star 30.  The tin cure will be a bit more durable, but the platinum cure does not require vacuum degassing, which is one reason platinums are so popular.

    If you really want rigid parts you could use a urethane resin like the Smooth-Cast 300 series from Smooth-On.  https://www.smooth-on.com/category/urethane-resin/

    For your primer question.  When I paint on resin with acrylics I don't normally use a primer.  I just lightly sand the part to give it a slightly rough surface and then clean/de-grease it using 99% isopropyl alcohol while wearing gloves to make sure oils from my hands don't contaminate the surface.  After that I'll either airbrush in a base coat, use sponges, brushes, etc.

    Hope all that helps!

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