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Manual kiln firing (A.F.C kiln)


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Hi, I just acquired a manual kiln that has a pyrometer.  The potters i know have given me firing schedules for kilns with digital controllers. But now I’m confused (I’m firing to cone 10).  I can’t see how to finely control the ramp rate or soak on my kiln. So then I went down the rabbit hole and found a great thread on manual firing (with a cone sitter) saying to divide the total fire time by the 3 settings (low/med/high).  Sounds easy enough but, how do I find out how long a 
cone 10 (1280 C) fire take? Or even a cone 03 1/2 (1080 c)?

Thanks in advance 

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3 hours ago, Tati said:

....how do I find out how long a 
cone 10 (1280 C) fire take? Or even a cone 03 1/2 (1080 c)?

To get a rough idea of how long bisque and glaze firings take have a look at the programs used by digital controllers. One here for example, which has a cone 04 fast bisque as taking 11 hours and 13 hours for slow bisque and a cone 10 glaze as 5 hours for fast and 8 hours for slow. These figures are relying on the kiln being able to keep up with the programmed rates, which isn't always the case. Small kilns can heat up like a rocket but larger kilns (or ones with worn elements) could very well not be able to heat at the same rates. What it will help with is with the pyrometer you can see what the temperature is at any given point and turn up or down the dials when that point is reached. 

3 hours ago, Tati said:

I can’t see how to finely control the ramp rate or soak on my kiln.

It's going to take fiddling with the dials while watching the pyrometer and lots of note taking to get it dialed in. Use witness cones so you can check your results rather than just going by the temperatures the pyrometer is giving you.

Welcome to the forum.

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The typical firing schedule used on manual kilns is one hour on low, one hour on medium, then high till the Sitter shuts it off. You can't easily mimic the controlled rates of climb that are used in digital kilns without sitting there watching a pyrometer and turning switches on and off every few seconds, and it's not necessary. Only the last 200 degrees really have much of an effect on the finished glaze, so don't over think it. Your kiln is unlikely to go too fast at the high end, but if it does, you can just spend more time on medium before switching to high. The good news is that people have been making beautiful work with manual electric kilns for decades!

Also, I would recommend not firing to cone 10. You'll cut your element life in half (or worse) and wear out your kiln much faster firing that hot. Most cone 10 glazes can be dropped to cone 6 with the addition of a few percent of boron-containing frit.

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