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andros

Umpteenth question on raku kilns

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Hi folks!

I've just been given to me what I hoped to be my first own electric kiln. It's a very very small stackable top loading kiln. The chamber is more or less  a cube with 12"\13" (32cm) side. Microscopic but mine!

Unfortunately it doesn't work... (:() because it's not able to go above 1300F (700°C)... It's too a small and old kiln to spend money to replace the heating elements, even because the control unit is very "primitive" so I would have very small control on temperature rising velocity ecc..

Just to not toss everything, I thought to convert it in a updraft raku kiln. It's a lot of time I've planned to build one raku kiln and I think that this can be a good occasion since I can save the cost of the isolating blanket.

I'm little scared that the kiln will be just too small to have an evengas  heating but at that point the cost of a barrel and a ceramic fiber blaket will be not so high...

I read a ton of threads here and elseware but just I couldn't find out an indication on what the diameter of inlet and oulet should be... I will use a  weed burner with a torch diameter of 6cm so I thought to make both the inlet  (in the bottom) and outlet (in the lid) of 8cm... I need to buy and use a hole saw  (and I want to retain the "scrap") so I want to be pretty sure that I'm  not going to enlarge it because are too small...

I'm going to put a cordierite"flame spreader" 5cm high above the inlet hole.

Somebody could give me some tip or tell me if this stuff will never work properly??

 

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With something that small you  can probably do just about anything and get it up to raku temps. I think your plan to make the holes at 8cm is a good place to start. You can block off the exit flue as needed with a kiln brick or post. The thing you'll have to watch is overpowering it. There's not a lot of room to move air through a space that small, so keep that burner throttled back.

andros likes this

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Thank you for the reply!

In order to ensure enough air moving iside the tiny chamber do you think that some sort of chimney will help? I'm going to keep the control unit, not indeed to control the heating elements (that has already been cut off) but because I need the reading of pyrometer (that probably will be pretty out of calibration but I can compensate it with some try with cones) so I could do without the possibility of peeking through the chimneyf... And anyway i could do some sort of peephole...

This is just a temporary solution anyway... In a (I hope not too far) future I will replace it with abigger  ceramic fiber chamber... is someone albe to figure out what is the maximum volume heatable with a weed burner with a nominal power of 80 KW (about 273.000 BTU?)

 

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A little chimney certainly wouldn't hurt. You'll definitely want a peep hole. The best way to fire raku is to look in and watch the glazes. They'll bubble up, then settle down and gloss over, then they're ready to pull. Cones won't work, it's too fast a firing. The pyrometer will be a good indicator of how fast it's climbing, and for peak temp, even if it's not accurate. Do the first load by watching the glazes and take note of the pyrometer reading, fire additional loads to the same reading.

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