Glass Fusing Kiln

3ft x 6ft top hat glass fusing kiln with silicon carbide hearth & fiber insulation

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Wanted kiln capable of fusing 3ft x 6ft glass art. Kiln has top and bottom elements with a suspended hearth of silicon carbide tiles and fiber insulation. Quartz windows. Computer controlled heating programs and venting.
  • 80 × Ceramic Fiber Insulation Modules 1" thick ceramic fibers oriented perpendicular wall plane. Compressed onto a stainless steel mandrel and banded at 300 PSI. Tightly installed, the bands can be cut while still keeping the insulation under compression. Installation is "finished" off by hammering their kiln-side surfaces with a 2x4 and then spraying them with silica rigidizer to prevent dust. Temperature rated to 2300F.
  • 40 × Mullite Tubing - 1" x 40" These support the Kanthal heating elements. They are almost as strong and heat resistant as alumina, at a fraction of the cost.
  • 4 × Insulation Board This was used as a support for the lower element tubes below the hearth. It is not suitable as wall insulation.
  • 8 × Silicon Carbide Hearth Tiles 18" x 18" Recrystallized silicon carbide forms the hearth tiles in 2 rows of 4. It is strong, flat, dora not warp and transmits hear relatively well for a refractory. It is also less susceptable to thermal breakage.
  • 5 × Silicon Carbide Beams The hearth tiles sit on a series of 2"x2"x2' silicon carbide beams which run the width of the kiln.

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RandyKC wrote 10/09/2015 at 18:02 point


Thank you for posting this on the website.

I have an L&L kiln that I'm satisfied with but want to build a smaller kiln for copper enameling and your design has some elements I'll use for that.

Adam, here is a link to Bruce's website that also explains why they are so busy:

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bdh.dimagin wrote 10/10/2015 at 07:50 point

Hello and thank you. 

L&L makes well designed kilns; I particularly like their element shields.

Good information on standard kilns can be found at: and 

Zircar also has  good high temperature kiln info: look for technical papers at

Here is another link to my kiln and I have a longer PDF by request.

I haven't built one, but you might try a fiber lined cylinder containing a spiral heating element wound around the inner circumference. It might provide very even heating. Place the work to be heated on the midline.

Best, Bruce Hubbard

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bdh.dimagin wrote 04/20/2015 at 08:07 point

Hi ab (duplicate  post):

The kiln just sort of happened. We had a 17" Evenheat and wanted something larger. I had a background in studio ceramics and we were thinking in terms of brick "bath tub" kilns. By chance, we encountered a Skutt GM22CS, a sweet 24" kiln whose design I still admire. It was too expensive at the time, but it introduced us to totally new ways of thinking. I also spent a summer at Pilchuck and got to see large professional kilns by BVD and Nabertherm and others. A mutual friend introduced me to a great NASA thermal engineer about that time and I began to seriously study kiln design and heat. My most useful discovery was: "Make friends with sales engineers - they know a lot". As we realized that we could build a really nice kiln, my wife and I talked ourselves into larger and larger designs, with the available power coming into our studio finally setting a firm upper limit. The design evolved over several years as we collected components and finally being laid off in 2007 provided me with 6 months of free time to work on actual construction. I started in ernest in August and we saw "first heat" just after New Years. It lasted about 5 minutes and then a 100A breaker blew, but it was still a thrill.

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Adam Fabio wrote 09/11/2014 at 06:20 point
That kiln is a monster. I'm wondering if you could do telescope lenses in there. Could you upload images of some of the projects you've made with it?

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bdh.dimagin wrote 09/12/2014 at 08:46 point
Hi Adam, I have actually thought about this - fusing 12"-14" mirror blanks, but the viewing is too poor in LA where I live and there is already a cottage industry of people casting mirrors, so I decided not to work on it as a personal project. (Or you really considering a refractor lens?) Either way, the biggest issue is the annealing time for thick glass, even if it is honeycombed. Micro-bubbles and unwanted inclusions are a secondary issue. Pyrex (2150F) also wears out the kiln faster. We have a smaller kiln which might still be good for a 12"-14" window glass blank and not compete with our other projects for available power. (The big kiln maxes out our 100A feed.) Aside from raw power, optical glass requires very slow annealing - probably at least 5 days/inch thickness (4F/hr). I anneal think art pieces about 5 times faster and it is still a slow process. I'm not sure that I could beat anyone on the cost of Pyrex, however, unless I fused 8 mirrors at a time and had orders for them. How big a mirror are you thinking of? My astronomy friends tell me that past 12", one needs active optics to correct for atmospheric distortion and realize the full benefit of such a large mirror. I've actually seen some pretty nice deep space photos from 4" refractors equipped with star trackers, precision mounts, and low noise CCD's - probably $10,000 worth of equipment.
I don't have time just now to look for projects, but here is an ArtSlant link which shows some.

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