Silicone Rubbers cover most mould making requirements; by various combinations of rubbers, catalysts and Thixo Additive, a wide range of viscosities, strengths, and properties can be obtained. Room Temperature Vulcanising (RTV) Silicone Rubbers (i.e. cold cure) make moulds with working temperatures of 50ºC 250ºC, making them suitable for use with a wide range of materials, including plasters, cements, polyesters, epoxies, urethanes, waxes etc. and RTV-101 is a firm rubber going to 316ºC, making it ideal for use with tin alloys and pewter (both hand casting and with the Centricast Machine – see later section).