What does "RTV" mean? May 06, 2020 18:45 Updated RTV stands for Room Temperature Vulcanized. This refers to a material that reacts and hardens at room temperature. Related articles What is a test cure? What is casting? Is it necessary to vacuum or pressure cure clear urethane products (like Poly-Optic)? Where can I view the Polytek product catalog? I'm doing a concrete mold making project for the first time - where should I start?