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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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Hi Tati, I too have acquired an AFC manual kiln that is in some state of disrepair and was wondering if you have an instruction manual as I'm not even sure if it has all the working parts... let alone how to operate it... I am very new to pottery and am doing lots of research online but would appreciate any insights from another AFC manual kiln owner!? 

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Hi Caro!

I'm not finding much on "A.F.C. Hi-Tech Kilns" other than dated pictures* from an auction site, and controller manuals.

Given your kiln heats up and is set up to run safely - fumes, heat, adequate power supply, etc. - there's not much more to it; for a manual kiln, we are the controller.

I've started out with a fully manual well used kiln (Skutt KM1027, new in 1988). I've fitted it with a pyrometer, which provides helpful feedback. The first several firings, I'd placed firing cones where I could see them through the peep holes (kiln glasses are an absolute must against rays, heat, any flying bits), so I might shut down when target temperature had been achieved. Since, I watch the pyrometer reading and look at the firing cones afterward. For glaze fire, I run up to 200F the night afore, then ramp up to cone 5 (my target) on high the next day; from there, I'm dropping 100F for a hold, so there's some switch manipulation and close attention involved.

Perhaps you will also find pyrometer and firing cones helpful. May I also suggest keeping detailed notes - time, temperature, details!

*The only pic I found, am guessing this is electric - looks like a controller box mounted below ...what does your kiln look like?

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Edited by Hulk
*
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@neilestrickgave you good advice as did others. Most electric kilns unless really designed for ^10 specifically will not fire there efficiently burning the elements out quickly.  I have fired a cone 10 L&L manual kiln to ^6 for years. In the beginning I relied on cone packs and for a while a pyrometer. However in the last 10 years or so have relied on myview of the heat color coming out of the kiln peeps of the crack between lid and body. I usually fired slowly up to 1000F. then shot to high for the rest of the firing. Cone 6 looks like Yellow White. . . very bright, No orange. 

You may look up a color temp/cone chart to become acquainted with color temp changes. Easy to follow, and with a few firings you will know when your cone packs will start to respond to the heat work in the kiln. All of this IMHO.

 

best of luck,

Pres 

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