RTV Silicone, also known as room temperature vulcanization silicone available in a hardness range of very soft to medium, is a type of silicone rubber made from base plus curative, which is a two-component system. Ranging from 15 Shore A to 40 Shore, RTV Silicones can be cured with one of the two- a platinum catalyst or a tin catalyst.

RTV Silicone rubber is said to have a lot of advantages over rubber which is a direct result of its unique characteristics. For example, it has favourable tension and hardness. It is said to have light viscosity and good flowability. RTV Silicone has very low shrinkage and absolutely no deformation. With high temperature resistance, ageing resistance and acid and alkali resistance, it is known to have good characteristics of easy operation.

RTV Silicone produces the finest detail and has a wide variety of operations, some of which are – usefulness as a cast to a number of materials like polyester resins, epoxy, wax, gypsum, low melt alloys and metals; suitability for industrial and art related applications like architectural elements, sculpture, furniture and prototypes, etc.

While making a mould by RTV Silicone, we must remember a few points. RTV Silicone rubber will look like a white liquid, semi-flowing, with a hardness of 22-40A after curing has taken place. Contrary to popular belief, Silicone oil is not to be added to Silicone rubber. More curing agent is needed if moulds require fast drying and demould and less if they require slow drying and demould.

It has a number of advantages.  When doing production casting of resins, mould rubbers are required to have good release properties. RTV Silicone is known to have the best release property among all rubber moulds. There is no post production clean up as no release agent is necessary. Good chemical resistance and high temperature resistance are some other good qualities of RTV Silicone. It can bear up to 400 degrees Fahrenheit, which is equivalent to a 205 degrees Celsius. This particular characteristic of Silicone renders it the only mold rubber in existence, that is suited to cast low melt alloys. Thus, good release property together with heat and chemical resistance makes it a superior choice for production castings.

However, we may note here that RTV Silicone is not all advantageous. It has a lot of disadvantages. As far as the cost structure is concerned, RTV Silicone is not one of the cheapest options for casting and other industrial operations. Platinum cure is more often than not rejected because of its high cost. Sensitivity to materials like sulphur clay often prevent the Silicone from curing. This process is called cure inhibition. Sometimes the use of RTV Silicone may lead to a phenomenon called bubble entrapment. This occurs if the high viscosity Silicones are not vacuum degassed before pouring. If during the process of making a brush on rubber mould, the time factor is long, Silicone components A and B will refuse to work if they are not mixed accurately by weight. It must be noted that tin catalyst Silicones do not have a very long library life.