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Roshini 2013-05-23 5:07am

kiln questions
 
I'm planning to get a kiln custom made, as I'm based in India, and the ready kilns will be too expensive considering import duties and shipping. I have a few doubts,

1)Since I'm more into sculpting, I hope to have an internal chamber about 1'x1'x1', front opening. What is the max size of glass I can anneal in it?
2)Most often I'll use the kiln to anneal small pieces 1-2" in length. Will that lead to energy wastage since the chamber is large? Also do you'll keep the kiln at annealing temp the whole time you work to keep popping thing in as u make them? My work develops little crack while cooling.
3)Where is the best place to have the heating elements located so that the heating is uniform? Is it common for a kiln to be ventilated for even heating?
Does it matter if the insulation material is ceramic fibre and not fire bricks if the ceramic fibre is completely covered with steel from all sides? Since ceramic fibre is cheaper than brick.
4)How long does it usually take a kiln to reach annealing temp from room temp?

Maybe thats more than aa few doubts... :mrgreen:8-[

istandalone24/7 2013-05-23 9:31am

1) you can anneal whatever you can fit in it.

2) you'll want to program your controller to garage temp and hold it there, so while you work you put pieces in there as they get done. once you're done torching, start the annealing cycle.
if you're working on a big piece, you'll want to pop it back in the kiln every so often to keep it's temp up.

3) i like elements in the ceiling of the kiln....but then again the only kiln i've used is set up this way so i'm biased. i don't think kilns are vented, but ?
ceramic fiber sucks. big time. firebrick is worth the extra $ in more ways then one. it also holds heat better.

4) depends on the kiln. mine, about 40 minutes at full power (to 1000f garage). your mileage will vary with different kilns.

Roshini 2013-05-24 3:09am

Thanks! I'll keep those point in mind.

FosterFire 2013-05-24 7:31am

If you can find a copy of Bandhu Scott Dunham's books, they have the most detailed explanations i have seen in print. He goes in to how big=how long for annealing. Right now you can use a bead annealing schedule and it will be fine, but if you go very thick then it needs to be a longer soak time with a longer cool down. I recommend a digital controller.

28676bhe 2013-05-24 6:07pm

You may be developing cracks because you're putting the beads into a cool kiln instead of waiting for it to reach the garage temperature. Or, your kiln may not be keeping the temperature steady enough while you're working and cooling and heating in too large of a range.

Largest item? You do need to leave a bit of room around for proper heat sharing and to avoid cool spots. Most often you need to raise the kiln shelf off the floor - so I'd say no larger that a 9x9 or 10x10.


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