Silicone Putty Seashell Mold for Kids

February 8, 2017

This is a fun and easy project to do with kids. You can simplify it by making it a simple one piece mold and/or leaving out the colorant. I find that seashells are an easy shape to mold from the silicone putty. Other small, simple shapes can work as well.

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:

  • Make sure everybody is wearing gloves.
  • Place your seashell on one of the small pieces of cardboard. The cardboard should be a few inches bigger all the way around than the seashell.

  • Separate out equal parts Silicone Putty Part A and Part B. This product isn’t especially fussy. You can measure out the parts visually and see that the two parts are approximately equal.

  • Use your hands to squish the two parts of Silicone Putty together, folding and mushing it until it is all mixed together and one uniform color.
  • Press the Silicone Putty over the seashell, starting at the top and smushing downward. Make sure to press around the edges of the shell. Don’t press down so much that that silicone becomes very thin. You want the silicone putty to be about a quarter inch thick.

  • Lightly press the second cardboard piece on to the top of the Silicone Putty. Thiscreates a flat spot for the mold to set on when its time to pour resin into the mold. It should look like a cardboard-silicone sandwich. Try to get the cardboard as even as possible.

  • Let the Silicone Putty cure for at least 20 to 30 minutes. This type of silicone (platinum catalyzed) can be affected by the cold, so if it’s chilly (under 68F), let it sit for a little longer.
  • After the Silicone Putty has cured, remove the top piece of cardboard and peel the mold off the bottom piece of cardboard.


  • If you are doing a one part mold, You can pull the shell out of the mold and skip ahead to the resin mixing and pouring part of this post.
  • For the two part mold, leave the shell in place. I usually cut some notches with an X-acto knife to help me line up the bottom and top parts of the mold. This isn’t 100% necessary. However, it does make it make it easier to line the mold halves up.

  • Next we need a silicone-to-silicone mold release to keep the two halves from sticking together. I used an aerosol called Petrolease, but plain petroleum jelly brushed on to the silicone works just as well. Make sure you get the mold release into the notches as well. You want a good barrier so that no part of the silicone will stick together.

  • Mix together another batch of the Silicone Putty and press it into the shell and onto the silicone, taking care that it fills any notches that you may have cut.
  • Let the silicone cure for 20 to 30 minutes. Once it is cured, separate the two halves and remove the seashell.

  • Measure out equal parts of Casting Resin Part A and Part B. If you are using colorant, add it to the Part B before you mix the two parts together. Mix well with plastic utensil/stir stick, scraping the sides and bottom of the mixing container.

  • If you are doing a one piece mold, pour the mixed Casting Resin into the mold, filling it up.

  • If you are doing the two piece mold, fill the mold cavity up about half way and then place the convex part of the mold gently on top, lining up the notches. A little Casting Resin will squish out of the Silicone Putty mold. That’s okay because this shows you that mold is completely filled. It is also why this type of mold is frequently called a squish mold.


  • Let the Casting Resin cure for at least 30 minutes, a little longer in colder weather. Then pop your new seashell out of your mold and trim away any flash.

  Here you can see the difference between the one piece mold and the two piece mold.

  • You can also multi colored shells by measuring out two sets of Casting Resin and adding to only one, or different colors to both.

  • If you can, have one person mix each color at the same time, or mix them very quickly, one after the other. Pour the colored casting resin into the mold at the same time. The slower you pour, the more swirled the colors will be. Just be mindful of the pot life.

You can use the Silicone Putty mold many times over to create an entire beach of seashells! You can find the products for this project and more information on our website,  You can always send us an email if you have any questions at




« Return