All PELCO Silicone Rubber Molds are made from the highest quality silicone rubber available. With care they will last a long time. After polymerization in a 60° C oven, let molds cool before removing blocks. This precaution will increase the lifespan of the mold. Using silicone rubber with Spurr's Resin will significantly reduce the lifespan of the molds. Maximum temperature: 218°C (425°F).