Making a Brushable Silicone Mold with Mother Mold Part 2 of 2

October 7, 2016

In the last blog post, we went over step by step how to make the brushable silicone glove mold. In this post, we will cover step by step how to create the mother mold which is the rigid outer shell that helps support the mold during casting. I will be creating this mother mold from water activated plaster impregnated gauze strips. These plaster strips can be purchased at most art and hobby stores, like Michael’s.There are other ways and materials to create mother molds, but I find this way easy and simple for beginners and for small to medium sized projects.

Materials needed

• Your original piece, with the silicone glove mold in place
• Water activated plaster strips
• Scissors
• A cup filled with warm water
• A manila folder or poster board or or other suitable thin, stiff paper
• Hot glue gun
• General purpose mold release ( I used an aerosol, but petroleum jelly is just fine too.)
• gloves

Your work area

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

Project steps

• If you haven’t already done so, make sure you break the seal between your piece and the silicone mold. To do this, just pull the mold away from the piece slightly, just enough to get a finger or two under the mold and run it around the piece. Make sure the mold then settles back into place and set the piece down at your work station.

• We’re going to create a parting line for mother mold out of the manila folder (or other suitable stiff paper). For this piece it’s going to be right down the middle of the skull. I cut the paper into strips about two inches high and an inch to two inches long. Use the hot glue gun to glue these strips in an even, unbroken line down the middle of the piece. The hot glue will hold them securely in place but will also easily come away from the mold when you are done. apply a light coat of mold release to both sides of the paper divider. This will help the plaster pull away cleanly when you are done.

• Next, cut the plaster strips strips into inch and half to two inch pieces and fill a cup with warm water.

• Wet the strips in the cup and work it between your fingers to activate and even out the plaster. Place the strips on on the mold, starting at the top. Create a flange by placing strips half on the mold and half on the paper divider.

• Lay the strips vertically or horizontally, whatever is easier for your piece. I did horizontally here because it makes the most sense for the shape of this piece. Overlap each strip to create a stronger mother mold. When you reach the bottom of the mold, DO NOT apply the plaster over the small bottom lip of silicone. Do both sides of the mold this way. Because this piece is on the smaller side, I only did one layer. If your piece is bigger, you can apply 2-4 layers of the plaster strips, alternating laying them vertically and horizontally for added strength.

• I let the plaster dry overnight, but you can always check what the recommended dry time is for the plaster strips you are using if you are in a hurry.
• Once dry, it should be fairly easy to pull the plaster halves off the mold and remove the paper divider. The mother mold should also be easy to put back in place around your mold once the paper divider is removed.

That’s it! You should now have a brushable silicone mold and a functional mother mold to support it when casting! When it is time to cast, you can keep the halves of the mother mold together with tape or clips. In our next blog post, I’ll go over how to use this mold to create a cold cast bronze piece.

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