How to Cast Urethane
- 1). Spray the inside of the rubber molds with a light layer of mold release agent. Place the two halves of the rubber mold together, aligning them carefully so that the edges of the impressions in the two molds match to get a full 360-degree cast from your urethane. There are usually several protrusions surrounding an impression in one mold that slide into holes surrounding the impression in the opposing mold to aid in alignment.
- 2). Place thin plywood panels, cut to the size of the mold face and back with a utility knife, against both sides of the mold. The panels ensure that there's no deformation of the mold as you're casting. Secure the panels in place with rubber bands placed around the top of the sandwiched mold and around the bottom. Set the mold onto a flat surface with the pour hole to the top.
- 3). Mix the two-part urethane compound, using the mixing ratio provided by the manufacturer, in a clear plastic cup using a wooden stirrer. Pour the urethane into the mold through the pour hole at the top. Tap the side of the mold with the stirrer as you pour to force any forming bubbles to the surface of the liquid. Fill the mold with the urethane and then wait the curing time recommended by the manufacturer for the urethane to harden.
- 4). Remove the rubber bands and the wooden panels from the mold. Gently pull the two halves apart, revealing the urethane casting within. Pull the hardened urethane completely from the mold and wipe with a clean cloth to remove any residue of mold release agent.
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