Kiln forming

Most of the glass I make has at some stage been manipulated in a kiln.
My studio pieces are all "Kiln-formed" which is a two stage process involving the fusing of glass and then forming or slumping over moulds.

The various pieces of glass used must be compatable or expand/shrink at the same rate when heating/cooling. This is referred to as the Coeffient of expansion (COE). The glass I use is Spectrum System 96 which has a COE of 96 and is imported from the USA.

Glass is cut to a design then laid out on a kiln shelf covered with kiln-wash. Textures can be applied to the shelf under the glass using thicker kiln wash; ceramic fibre paper; silica/plaster moulds etc. and crushed glass or frits applied for added effect.

The glass is then placed in the kiln and heated to 780-800 deg C according to the desired level of fusing. At 780 deg, the contours of the individual pieces of glass will be visible but at 800 deg all the pieces will fuse to one level.

After fusing, the glass is cooled slowly and held at 512 deg - the annealing temperature for 20mins to hours (according to the thickness and size of the piece) to help reduce any internal stress and avoid cracking.

A second firing to around 650 deg C is then used to form the glass over a mould. My curved pieces are formed over stainless steel moulds but many other materials are used eg. Ceramic fibre board.

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