RTV Silicone Rubber

RTV stands for Room Temperature Vulcanizing and describes the way the rubber becomes solid. RTV silicone rubber is an inexpensive way to make multiple copies of a part or pattern. Because of the flexible characteristics of RTV rubber, you can reproduce some very detailed parts.

The hardness or flex rating of RTV rubber is measured on a scale called a Durometer in a value known as SHORE strength. The higher the number the less flexible the rubber or mold will be. As an example, a SHORE of 15 would be very flexible while a SHORE of 35 would be fairly firm, similar to a rubber band. A SHORE of 45 would be firm about like a bicycle inner tube and a SHORE of 65 would be a hard, tough rubber like that of a car tire. A SHORE of 15 to 25 is good for most modelers and hobbyist.

RTV rubber is offered in two types of forms of curing process, Condensation cure and Addition cure.

Condensation cure RTV cures through the evaporation of alcohol, hence the name "Condensation" cure and it must used in an open or vented area. This is the most commonly used RTV curing process and is the type I recommend for hobbyists.

Addition cure RTV has no chemical reaction or by-product and therefore will cure in a closed environment. Its curing can be accelerated with mild heat. Due to its sensitivity to heat, I don't recommend this type for the average hobbyist.