An introduction to materials for glass moulds

The materials used to make glass moulds should comply with a number of requirements that are often contradictory. Cost and speed are key factors in this business. The mould cavity that forms the gob must be durable and sufficiently strong. Contact between the glass and the mould cavity should ease glass settle. Checks should be made to ensure that there are no defects in the cavity surface, which could harm the same surface of the glass, causing cracks and effects such as 'orange peel' or soiling due to carbon build-up. Finally, contact between the glass and the mould should not result in a chemical reaction between the two materi- als. The capacity of the mould material for channelling heat from the glass to the ambient environ- ment is expressed in terms of its thermal conductivity. The glass production cycle is closely linked to this characteristic of the mould. In this work, different materials used to produce glass moulds are described with particular attention to the cast iron family.