Learn Mold Making Basics for Jewelry

In my last article on the art of lost wax casting, I discussed how to make an original pendant design in wax, cast it in metal, and turn it into a finished sterling silver pendant. This is something I do all the time to make the jewelry that I sell online and at my shop, Dragon’s Treasure in Fresno, CA.

Now say that you have made a pendant that you really like. You like it so much that you want to make copies of it. How do you do that? You make a mold of it. Though there are many different kinds of molds, I’m going to talk about vulcanized rubber molds.

To make a rubber mold you will need your original pendant, a mold frame, rubber mold making material, a pair of good size sharp scissors, lots of curved-edge scalpel blades, and a vulcanizer. A vulcanizer is a machine that modifies rubber with heat and pressure. You will also need a propane torch and a bent nail.

The first thing I do when I want to make a mold is to take my original pendant and make sure it’s as perfect as I can make it. I polish away any rough spots and make sure all the detail I want is in place.

Next, I lay the mold frame flat on the table. The mold frame will hold everything together.

There are different materials available to make molds. I use a natural rubber material that comes in large flat sheets. I take a sheet of the rubber material and cut out rectangles the same size as the hollow in the center of the mold frame. I put a layer of rubber in the bottom of the mold frame. Then I put my original pendant down flat in the center of the rubber layer. I put smaller, cut up pieces of rubber around my pendant, filling up the free space around it. I put another layer of rubber over the top.

The mold frame is now full of layers and bits of rubber, with my original pendant in the middle.

I place the mold frame on the bottom platen of my vulcanizer. A vulcanizer is a heavy duty machine with a wheel on top. I turn the wheel to lower the top platen, sandwiching the mold frame between the two platens. The vulcanizer applies heat and pressure to turn the layers and bits of rubber into a solid block, with my original pendant embedded in the center.

Once the mold cools, I push it out of the mold frame. Then I use a curved scalpel to very carefully cut across and down the sides of the rubber block. I am not trying to make the cuts flat, but irregular, almost jagged.

The rubber dulls the blades quickly. It is better to replace them often than to use a dull blade, which is both dangerous and doesn’t help the mold either. I peel the top of the mold back as I work, being careful not to damage the embedded pendant with the scalpel.

When I have finished removing the original pendant, I’m left with a two piece rubber mold.

Hold the two pieces of your mold together. See how the jagged cuts make a tight fit? If the sides are cut smoothly the two pieces would slide around and make it very difficult to use.

Finally, I heat a bent nail with my propane torch until it is red hot, and I use the nail to burn a channel from an inconspicuous spot on the pendant’s impression to the outside of the mold. My mold is now ready to use.

Next you will need a wax injector, injector wax, and two pieces of either metal or plastic, slightly bigger than your mold.

A wax injector has a pot with a tall plunger in the center. I pick up my two piece mold, holding it rigid and flat with a glass plate on either side. This keeps everything from moving so your new waxes will be crisp and detailed. I place the hole of the channel on top of the plunger, push down, and melted wax is injected into the mold.

As the mold cools, the wax will harden. Then I slowly pull the two pieces of my mold apart and carefully remove the new wax model of my pendant so I don’t break it.

Now I have a wax pendant just like the original wax model I made. With my new mold I can make as many of the wax models (and the pendants!) as I want.

I can turn my new wax models into sterling silver pendants by following the steps in my first article on lost wax casting.