How to Make a Rubber Mold of a Figurine

Moldmaking is the most common way to translate a model design into another material and lets you make multiple identical copies of the model. One type of mold used to copy figurines is the rubber mold, which is a flexible mold that does not ruin the original object. The best method for making a rubber mold of a figurine is the two-part process, which creates a mold that separates evenly down the middle.

Things You'll Need

• Figurine
• Legos or cardboard
• Modeling clay
• 1 quart silicone RTV rubber
• Plastic cups
• Stirring tools
• Wooden craft balls
• Rubber bands
• Razor blade

Instructions

Make the First Rubber Mold Impression

1. Create a moldmaking box with an open top and bottom that is large enough to enclose your figurine. You can make the box out of Legos if the figurine is small or out of pieces of cardboard taped together. Make sure that the box is at least 1/4 inch larger than the figurine in all dimensions.

2. Flatten a piece of modeling clay on a work surface so that you have a 1/2-inch--thick rectangle that is slightly larger than the bottom opening of your box. Place the box onto the modeling clay, creating a bottom. The box does not need to be rectangular or square, but it must be larger than your figurine in all dimensions.

3. Mix together no more than half of your silicone rubber with its catalyst, using a plastic cup and a stirring tool, such as a wooden dowel or Popsicle stick. Make sure that there are no air bubbles in the mixture.

4. Pour the mixture into the box until it is half filled.

5. Press the figurine into the rubber, making sure that it is half covered. Do the same to several wooden craft balls or marbles, making impressions around the figurine. These impressions will help you fit the mold together later.

6. Let the mold sit for at least 12 hours so that the rubber hardens.

Finish the Rubber Mold

1. Remove the craft impression balls from the first half of the mold. Mix the rest of the silicone rubber and catalyst.

2. Pour the silicone rubber mixture into the box, over the figurine, until the box is filled and the figurine is completely covered.

3. Let the mold harden for 12 hours. Remove the mold halves from the box and pull them apart gently, then take out the figurine. The mold should separate with little trouble, as silicone rubber does not easily stick to itself.

4. Put the mold together, making sure that the edges and impressions line up on each half. Bind the mold halves with rubber bands.

5. Carve a small hole in the bottom of the mold using a razor blade. Make sure to carve the hole deep enough to reach the figurine impression cavity on the inside.

Tips & Warnings

• To determine exactly what quantity of rubber you will need, you need to know the liquid capacity of your molding box. One quart of rubber should be sufficient for a small figurine. If you are working on a large figurine, the rubber also comes in half- and full-gallon jugs.

• You can purchase silicone RTV moldmaking rubber online through most art stores, as well as molding and casting suppliers.

• When the mold is finished, you can pour your casting material directly into the hole you carved. Take the mold apart again once the casting material has dried.

• This method will work only for figurines that do not have holes or openings in them. If you need to make a mold for a hollow object, you should create a 3-part mold instead.

References

• The Prop Builder's Molding and Casting Handbook

Resources

• Alternate Casting Tutorial