This material, supplied by us, replaces the usual organic rubber and is designed to satisfy the exacting requirements of manufacturers of high quality jewellery in their mouldmaking for lost-wax casting. In its vulcanised state it is highly flexible and durable with a good “memory”. It retains its properties for a very long time. One important advantage of elastomer is that talc or silicon release agent is rendered unnecessary. This eliminates another potential source of porosity in castings. Mouldmaking time is reduced. Elastomer cannot be burned like organic rubber. Additional sprues must, thus, be in the form of metal rods attached to the master or cut into the mould with a straight-bladed scalpel. Unlike organic rubber, the mould frame does not have to be overfilled with elastomer. Vulcanisation time is 2 minutes per 2 mm of mould thickness at a temperature of 190 °C (374 °F). Shrinkage during vulcanisation will be about 1% only.
Available in two dimensions: 7 mm diam. x 16 mm h. and 7 mm diam. x 22 mm h. Completely pack the mould frame with rubber and then position the four pins. After vulcanisation, withdraw the pins using a screwdriver and cut the mould. After cutting, push the pins back in. The mould may then be opened and closed without any loss of accurancy and there will be no tendency to “skid” during wax injection.
1. Metal sprue former 2. Casting master 3. Mould frame 4. Elastomer (Silicone rubber) 5. Mould frame aluminium plate A. Hole in mold frame B. Sprue former reference pin