Does the cast need any surface preparation prior to laminating with urethane rubber?
Urethane rubber has adhesive qualities. To prevent the urethane rubber from bonding to the cast surface, proper preparation is required.
First, the cast plaster must be thoroughly dry. We recommend baking the cast in an oven set at 150 f / 65 c for 24 hours prior to laminating with urethane. This will ensure evaporation of all trace moisture.
The cast must then be sealed to prevent urethane rubber from grabbing onto micro-porosity on the surface. We recommend applying two coats of Renew Sealer for this step.
Next, the release agent is applied. We recommend applying two coats of Mann Ease Release 200 release agent. (Note: Be sure to brush the surface with a clean, dry paint brush in between coats.)
By following this procedure properly and thoroughly, the urethane rubber should not bond to the cast surface.