Master Mould

High melting alloys

Silicones are also used to make the master moulds needed to form the gypsum or resin moulds into which high melting alloys like porcelains can be poured.

The phases of this process are as follows:

• An original model is produced, normally in clay
• Gypsum is poured over the clay model and, in the case of a complex shape, a number of semi-moulds produced
• The gypsum mould is removed from the clay model. More often than not, the clay model breaks at this stage
• Silicone is poured into the gypsum mould. The silicone master mould produced in this way is a perfect copy of the original clay model
• This silicone master mould can be used to produce many gypsum moulds for making finished items.

The key characteristics of these silicones are:

• zero oil content for maximum dimensional stability
• excess silicone can be removed easily, especially from the joins between two gypsum semi-moulds. Silicone can be removed with a micromotor or sandpaper as it is easy to trim
• low viscosity
• short polymerisation times
• adequate mechanical properties.