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1 May 2017

Glass working techniques: Kiln formed glass designs

What is Kiln forming?

Kiln forming is when the heat within a kiln and gravity are used to manipulate the shape of glass.  In essence, it is taking mass-produced float glass and reworking it to create a bespoke textured glass panel. These panels can be toughened and techniques such as sandblasting, painting, and the bonding of other glass pieces to the surface can be used to add further surface decoration.


kiln formed glass
A kiln formed glass panel with etched, painted, and bonded detailing.


How is it created?
Firstly it is important to ensure that the kiln furniture is totally even. A refractory material (capable of withstanding the temperature inside the kiln) is then placed onto this kiln shelf and worked into a negative of the glass design . In this blog we will show two different refractory materials being used: fibre paper, and then a plaster / flint mix created in-house by our studio team.


kiln formed glass imogen
Glass Technician, Imogen, creating a surface design using fibre paper.


In the above image, Imogen is creating a kiln formed glass design using fibre paper – a thick refractory material that holds its shape once compressed. Using fibre paper, sections can be cut out to create dramatic changes in the surface texture (as shown in the centre of the image above) or the fibre paper can be pressed down to create softer surface designs.


refractory mould
This refractory mould is created using a plaster / flint mix spread over kiln paper.


Above is a free form drawing in a mixture of plaster and flint. This plaster / flint mix was spread over kiln paper and shaped into a boat design by Daedalian Glass Studios Founder, Davia Walmsley. The advantage of using this mix is that it is very soft and pliable, allowing it to be manipulated easily and quickly spread into the desired form. Whereas using fibre paper to create a moulded design is comparable to sculpting, this technique is akin to painting.


refractory mould
Refractory mould with glass laid over them read to be kiln formed.


kiln formed refractory mould
Opening the kiln lid: the glass has slumped down and taken on the mould design.


Finally, a piece of float glass is cut to size and placed over the refractory moulds. As the kiln temperature is raised, the glass becomes malleable and takes a form similar in consistency to syrup. At this stage it and begins to slump down and fill the space beneath it, taking on the shape of the mould.

As glass is heated it expands and it contracts as it cools, causing stress on the glass (especially between the inner area and the surface of the glass). If this process is not carried out in a controlled manner, then it can lead the glass to break. Therefore, the glass is cooled down uniformly via a set temperature gradient (annealing), returning to a solid state with the design of the mould set into its surface.


finished kiln formed glass design
The finished kiln formed glass design.