RTV stands for Room Temperature Vulcanizing. A few years ago the molds were made from pure rubber, vulcanized under pressure in a aluminum frame. Due to the high temperature and the constant pressure, when the finished mold was finally released, cut, it had a 10% - 15% shrinkage from the original model that was made from. In recent years many experiments were made to minimize shrinkage.

The best solution was the Room Temperature Vulcanizing process where two parts are mixed together in a 10 o 1 ratio ( base + catalyst) and the curing process will be generated by the catalyst verses the heat with the regular rubber.

This mixture then will be vacuumed and poured over the master prototype and set aside to cure for 24 hours. When the silicone is fully cured, will be cut and hot wax will be injected in the cavity to reproduce the original several times.

Below are a few pictures of different molds and the injecting machine.

Click on the pictures to enlarge the detail.

Silicone mold suppliers:
www.romanoff.com
www.gesswein.com
www.riogrande.com
www.freemansupply.com

Silicone molds

The vacuum Wax injector