Silicone rubber is an ideal material for making molds of lifecastings and other objects used in sculpture, special effects and taxidermy. As with liquid latex, it yields a light, flexible, detailed mold, but has the added advantages of longer life, resistance to chemicals and decomposition. It is the recommended material for making long-lasting molds. A silicone mold also can be made in less time than a latex mold, if “fast” catalysts are used. Among silicone’s few disadvantages is that it is more expensive than latex, and not quite as elastic or tear resistant.

The most common silicone compounds used for mold making are RTV or “Room Temperature Vulcanizing” silicones that are mixed in two parts (a base and a catalyst) to induce curing. The silicone mixture is poured or spread over a prepared model or specimen, then reinforced with gauze or other reinforcing material between layers for increased strength and tear resistance

After the silicone mold is cured a shell mold is often constructed to provide rigidity for the rubber after it is demolded. The shell mold can consist of fiberglass, plaster or urethane. The shell mold is often referred to as a “mother mold.”
Normal curing time for most silicones is between 18- and 24-hours, but cure times may be greatly reduced by using fast-acting catalysts. When making molds in a studio where such equipment is available, de-airing in a vacuum chamber is recommended to remove trapped air bubbles. However, when working on larger molds vacuuming can be avoided by painting on the silicone over the model. The brush will tend to remove the surface air.
Safety Note: RTV silicone rubber compounds are relatively safe and odor free when properly used; however, the curing agents or catalysts may be toxic if ingested and are irritants to eyes and bare skin. Tinbased silicone cannot be used against the skin. Certain platinum-based silicones are deemed skin safe such as ArtMolds’ LifeRite……….to read more please download