July 12, 2017

This is a continuation of our last post about using silicone molds to modify a broken or fragile original part. In this post, we will go over sculpting in clay on the new piece and making a new mold. You can read the first part of this blog post here: https://www.aeromarineproducts.com/silicone-molds-to-modify-a-fragile-original-part/

Materials needed:

Your work area:

  • Clean, level work surface, covered in paper or plastic for easier clean-up.
  • All materials comfortably within reach.

Project steps:

  • Now that I have a original, I can use clay to sculpt directly on to it. I’m using non drying, sulfur free modeling clay. Because I’m using a non drying modeling clay, I want to make sure that what I’m sculpting will be able to be pulled from a one piece or clam shell mold. If I want to sculpt something more intricate, it would require a two part or multi piece mold. For a two part mold or multi piece mold, I would use a clay that air dries for sculpting and then use the modeling clay when making the mold. You can watch our video about making two part molds here: https://www.youtube.com/watch?v=jqwr8ZoH5E0
  • I decided I wanted my part to have two versions, unicorn horn and monster horns. I cast two parts in urethane casting resin from the silicone mold and sculpted the unicorn horn on one and the monster horns on the other. If you want to save on materials, you can certainly use one cast, make the mold, remove the clay and then sculpt on that part again.


  • I reused the same plastic containers for these new molds, so I mixed up the same amount of silicone (900 grams part A, 90 grams of part B catalyst) as I used for the first mold. Because of the detail of these pieces, I again used a chip brush to brush a thin coat of silicone on to the pieces before slowly pouring the rest of the silicone into a corner of the mold box.


  • About 16- 24 hours later when the silicone cured, I removed the original part.
  • I checked to make sure the humidity was under 50%, sprayed a little mold release into the molds and got ready to mix up my urethane casting resin.
  • The AeroMarine Products White Casting Resin is mixed 1:1 by volume. Urethane colorant is always added to the part B and well mixed before combining the two parts. Make sure to mix vigorously for about a minute with a plastic utensil and then pour slowly into the lowest part of the mold. AeroMarine Products Urethane Casting Resin is ready to demold in 30 minutes. Because of the shape of the part with the horns, I found it is best to demold right at the 30 minute mark when the casting resin is still warm and a bit pliable. It makes it much easier to remove the part from the mold. Once the part is removed from the mold, I set it aside to allow it to continue hardening and cooling off.

  • The cast on the right was colored with green urethane colorant. The cast on the left was painted with orange glow-in-the-dark paint with the horns colored with permanent felt tip marker.

The final results! All of these were achieved by a combination of colored resin, paint, and felt tip markers. As always if you have any questions, send us an email at info@aeromarineproducts.com.

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