Use either ComposiMold or ImPressive Putty for Urethane castings.

Polyurethane resin casting in ComposiMold

Urethane resin in ImPRESSive Putty

Quick tip for success with urethane casting resins and ComposiMold:

With ImPRESSive Putty, faster cure urethane casting resins work really well. The mold making putty can handle the higher temperatures of the fast cure urethanes.

For ComposiMold, choose a urethane with a longer cure time. These create less heat as they cure. You can also experiment with freezing the mold prior to pouring higher temperature urethane resins. Be sure to use talc powder/baby powder as your mold release before each casting made.

ComposiMold works very well with many urethane resins. However, there are two potential issues with some urethanes:

• Some fast cure urethanes create a lot of heat when they cure, which can melt the ComposiMold. You can work around this by chilling your mold first, adding fillers into the urethane before casting, or pouring the resin in intervals.
• Some urethanes are very sensitive to moisture. Use talcum powder as a mold release to reduce any moisture from the mold from reacting with the urethane.
• Use a mold release that is designed for polyurethane casting.

Urethane resins require dry fillers. Any water will create bubbles and heat. If you using powdered fillers in the polyurethane, dry the material in the oven at low temperatures for 15 to 30 minutes prior to mixing.

With ImPRESSive Putty almost any urethane appears to work. Because of the higher melting temperature of the ImPRESSive Putty, the faster cure polyurethane resins work well.

Pouring ComposiMold mold for resin casting

Making wheels from Urethane resin in ComposiMold mold