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kiln question

For discussion of processes related to using Bullseye glass, including kilnforming and kilncasting, torchwork, blowing and stained glass.

Re: kiln question

Postby bertglass » Mon Mar 22, 2010 9:02 pm

Mary Kay

I question what you say about "over insulation". I don't exactly know about this, but my feeling is that the problem is really caused by relatively high mass fire brick insulation. This material absorbs heat and then radiates it back in to the kiln. Lower mass fiber insulations may have a higher R value, but do not absorb and then give back the heat in the same way. They reflect the heat back in to the kiln. At the point at which you back off in power, the kiln cools much quicker.

There might be a point at which there is too much low mass insulation, but I have never experienced this in any kilns I have fired. Low mass insulation (fiber blankets and boards) are far more efficient than the higher mass bricks. I am not a fan of under insulated fiber lined kilns, that get very hot on their outer surfaces.

From a glass fusers point of view there is absolutely no advantage to a fire brick lined kiln (roof and walls). The advantage exists to the companies who have been making brick kilns for the past century. The one place in the kiln where bricks are an advantage is in the floor. They are the most stable material for making a flat nonwarping floor.

I totally agree that some brick kilns are more prone to causing devit.
Bert Weiss
bertglass
 
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