Which Silicone do I use ? RTV Silicone comes in many varieties, but the first thing to realise is that there are TWO main types. These are classified by the CATALYST used to turn the uncured, liquid, silicone polymer into a solid product. One is known as Tin Silicone, because its catalyst is a tin-based chemical, the other is Platinum Silicon. To further complicate this, often you will hear them described not by the type of catalyst, but by the manner of combination and vulcanisation (setting process). That is, Tin-based Silicones are also known as Condensation-Cured Silicones, while Platinum Silicones are Addition-Cured.