kiln building ?

[BobB]

I've searched the achives but can't find a comment I believe I read here. I'm building a kiln/furnace and i remember reading that ideally you want to have 1000watts per cubic foot for a kiln design.
What rule of thumb do you kiln builders use to insure you have enough power to achieve temps needed to fuse, slump and melt glass?

thanks
BobB

[Bert Weiss]

I've searched the achives but can't find a comment I believe I read here. I'm building a kiln/furnace and i remember reading that ideally you want to have 1000watts per cubic foot for a kiln design.
What rule of thumb do you kiln builders use to insure you have enough power to achieve temps needed to fuse, slump and melt glass?

thanks
BobB

1000 watts per cubic foot is more than enough power for fusers and slumpers. I see 800 -900 as being good. some people have 600 and are a bit slow to get to temp.

I am very unsure about which calculation is more relevant, watts per cubic foot or watts per square foot, when considering a kiln 12" - 18" deep. I have a feeling that an 18" deep box will reach the same temp as a 12" one with the same power, maybe a bit slower. The load you put in it has more effect than the air space.

Melting glass is another issue all together. I have no experience going above 1500. I'm think my kiln will make 1700, but beyond that I don't really know.

Talk to the tech staff at Duralite 860-379-3113. They are the experts on the engineering end.

[BobB]

thanks Bert, that's the real question I'm trying to answer. If I design for more watts/sq ft can I get to melting temps (2200 to 2300). I would think if 900 watt per sqft is adequate to get to 1500/1700 degrees, then 1000 to 1200 w/sqft should get me to higher temps. I'm sure other variables like refactories will impact this (ie. firebricks or frax, loaded or unloaded box, molds, crucibles etc.).

I'll try Duralite and see what they have to say.
thanks again.
BobB

[Ron Coleman]

Bob

Take a look at ceramic kiln design. The power you need isn't all that much. MY kiln is good for 2350 f and only has 775 wats per cubic foot. Reaching the top end takes a while though. At the high temperatures you're getting near the limit of standard coiled elements.

The biggest difference in high temperature kilns is material selection and adaquate insulation.

[Kevin Midgley]

My kilns run at the low end, about 600watts/ cubic ft. Sure more power will get you to fire a little faster but how many times a day do you want to fire a kiln? I am not into working a 24 hour day. It isn't the watts going into a kiln that is important, it is the total power that it takes to fire a kiln. My smallish kilns cost about 50 cents for a simple slump firing. With a bigger more powerful kiln, you'd better have full loads each time or your firings will be expensive. Kevin

[KILN-TEC]

Bob:
Make sure you inform your element designer that you want higher temp's than normal for glass fusing. A lot of glass kilns are built with "nichrome" elements which top out at about 1900 degrees. Fine for most work, but not if you're melting glass. If you use "Kanthol A-1" wire to make the elements they can reach 2400 degrees. Big difference.
Rich Edelman http://www.kilntec.com