Fiberglass vs Stone vs Silicone Mold for Creature


I am making a creature for a short film. It is supposed to be a worm-like monster that terrorizes a family over the course of the short. Here's the concept art:

After doing some research and learning about different options for how to achieve this, this is our plan:

1) Sculpt and mold a core, which we will cast with dental acrylic and cut up to make up the disks, head, and jaw used in the cable mechanism. This mechanism will be just like the one used for the Chestburster in Aliens (minus the arms).
2) Create a silicone skin by sculpting the creature onto the core, molding it, and casting it in some kind of silicone (Dragon Skin FX maybe, still looking at all our options), using the core in the final mold so that we get a hollow sleeve that we can put on our mechanism.

My team and I am pretty green to making creatures so any advice is valued, but specifically, I'm not sure what to mold the final creature with. Right now I'm looking at fibreglass, stone, and silicone molds but I'm not sure which would be best for this project.

Also, I have been looking for a place to buy dental acrylic and I haven't been able to find anything. Any recommendations?

Thank you very much!


  • Options
    Here's how I would make the creature.  This is just my approach, others might tackle it differently.

    I would sculpt up the creature in a clay like Chavant NSP or Monster Clay, then make an epoxy fiberglass mold of it.  Since the casting of the final skin will be flexible a rigid mold is ideal. 

    Once the mold halves are separated and cleaned I would lay up some clay into the mold to represent the thickness I would want the silicone skin to be in different areas.  This helps you control the weight and flexibility of different parts of the skin.

    Now the core can be created in a few different ways.  You can lay up fiberglass and epoxy in both halves of the clayed up mold and then join the halves together with more fiberglass or join the mold haves together and rotocast some resin inside for a hollow core or fill with resin for a solid core.  When the clay is removed you should be left with a rigid outer mold and an inner core. 

    Depending on how you design your creature you'll need to find a way to suspend your core in the center of your mold.  If the core can't lock into the outer mold (more on that later) you could suspend it using threads or small standoffs.  Then you'll need to add an injection point for the silicone, and likely add some bleeder holes in key areas to allow air to escape as you inject the silicone.

    For the way this character is designed in the concept sketch I would mold the head segment and body separately, as this would leave an opening at the base (neck) of each piece that would allow the core to lock into the outer mold by having a keyed flange around the opening.   It would also mean the silicone skin could be peeled off each core like a sock, and not need to be cut off.

    Hope that helps!


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