Kiln forming and casting

The highest temperatures can be used to melt glass in crucibles from which it is taken on blowpipes to form an amazing variety of products Cast glass uses high temperatures to melt glass melted so that it will flow into a mould. There are many variations on the basic technique At slightly lower temperatures and greater with time, glass pieces can be fused together, creating objects of different colours, textures and shapes With lower temperatures again, fused glass pieces and other cut forms can be slumped to a desired shape using gravity

At Torbay Glass Studio we use all these techniques except glass-blowing. For accuracy in temperature control we use electric kilns able to reach temperatures up to 800° Celsius. Where different colours or types of glass are to be fused, all the pieces must have a similar melting coefficient, an expansion measurement dependent on the ingredients used in the glass manufacture. Where this value is not close enough between two pieces to be fused, the finished article will inevitably separate on cooling.

The shape of glass in its molten state is dependent on its surface tension and viscosity. An understanding of these properties can be used to enhance design and detail in glass art, creating multi-coloured objects and panels comprised of fused glass or with patterned surfaces.

Cast glass involves molten glass being channelled into a pre-made mould. There are several methods:

• Glass pieces are arranged in a treated flowerpot and heated in a kiln until the glass melts and flows into the mould
• The glass is melted in a crucible until it is liquid, and is then poured into a mould, after which it is placed back into a kiln for annealing and cooling
• there are a range of Pate-de-vere techniques which differ greatly depending on the temperatures used. Glass pieces are arranged in a mould and the whole arrangement is placed into a kiln. It is then heated to melt the glass to the desired consistency so that it fuses, then it is cooled in a controlled process before the piece can be removed from the mould.