Adjustable Kiln/Annealer

Rev. 2000-7-9, 2002-02-25, 2009-05-04

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This page was originally created to help answer a question a glass forum.

Query: how to build a large fusing/sagging kiln without having to make a permanent investment.

Drawing of adjustable sided annealer

As shown above, the kiln is made with walls that butt into each other, a thicker lid in one or two sections and a lower deck. This way the deck is reusable. The walls can be reused to make a smaller space and the lid(s) can be reused.

Make the lower deck either from insulating castable (flatter and stiffer, not as good an insulator) or from frax and deal with the kiln shelf problem. In either case, a sheet metal tray, bent up from 24 gauge or heavier sheet metal holds the material.

Make the walls completely temporary using sheet metal to hold frax blanket, protecting the sheet metal from the heat with blanket. Make the lid, in one piece or two, from frax and fasten the elements to the lid. The key to the walls and lid is taking advantage of the low weight of frax and using thin layers of frax to protect the sheet metal as shown below. [It occurs to me even as I write this that the walls could be even more temporary, just sheet metal screwed to the lid or base, stuffed with frax.]


In the detail below we see that the sheet metal of the lid wraps around under the frax of the lid to support the lid and hold the frax in, while the sheet metal of the wall bends in to support the lid. Neither of the bends extends more than half the thickness of the wall frax to keep the metal from being damaged by the heat and to keep the metal from draining off the heat. A piece of soft 1/2" frax is placed between the two parts to seal the edge and insulate the gap. It is crushed down to about 1/4" by the weight.

The frax in the lid may be handled two ways: If the lid has a dimension under three feet, try to get 2" frax blanket. This has enough stiffness to span the gap. If it is larger, then plan on using a sheet of 1/2" frax board as the face with low temp frax blanket behind it. In either case, with care, the heating element(s) can be pinned to the surface. For a temporary rig, I would use heavy copper wire (less heat) through the side wall and down into the open space and small split bolts to make the inside connections.

I have had good luck/experience with my annealer built with layers of frax and this sheet metal technique, but mine does not come apart. Use sodium silicate (water glass, at ceramic supply places) as glue and make the layers as thick as possible. Because the frax extends beyond the metal, at the corners a bracket will have to be cut to bridge across.

I am working on, but have not tested, a kiln where 1/2" blanket is used to cover materials in the wall, the blanket being wrapped around, from under the sheet metal at the top, over the bulging frax and back under the metal at the bottom.

You can get away with things when you are using the equipment that would never work with students or random glass workers.

Drawing of sheet metal in frax annealer

Posted by Larraine on July 09, 2000 at 02:36:08:

To do a large scale piece of fused and slumped glass , is it possible to build a temporary kiln - by that
I mean one that can be pulled apart and adapted to other uses?? Can anybody help me on this one

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