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JFS

Issue firing kiln

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Hello,

Thank you to everyone for all of the information available here, has been a great resource for me.

Amateur potter and first time poster so please be kind...

Just received an old kiln (SNO industries P24) has a kiln sitter for controlling firing time. Also has a pyrometer.

I have fired a few bisque fires to Cone 06 and the cone has fatigued tripping the switch successfully but the pyrometer only read about 1200 F at its max. My first thought was that the pyrometer was faulty? First attempt to fire at cone 6 with glaze last night. Kiln climbed up to about the same temperature on the pyrometer but never tripped the switch (I waited about 11 hours) before killing the kiln manually.

I am mainly curious of any thoughts anyone has about my issue? Is it possible that the cone 06 cones malfunctioned and the pyrometer is correct?

Thanks, Jim

 

 

 

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Can you post a picture of the kiln? Is it an analog pyrometer? Is the pyrometer attached to the kiln system in any way, or just an add on? Typically in those old manual kilns the pyrometer is just there to let you know what's happening with the temperature, but isn't connected to the system in any way. The Kiln Sitter is wholly responsible for shutting off the kiln. The pyrometer or the thermocouple could be bad. 11 hours isn't necessarily that long to get up to cone 6, depending on the kiln. What's the max temp rating of the kiln? What condition are the elements in? Lots of pic will help, like an interior shot or two, the pyrometer, and the serial plate.

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Thanks Neil

Here are some pics, cant get inside because I have some pots in there now.

Not sure of max temp rating? How would I find that out?

Jim

IMG_1278.jpg

IMG_1274.jpg

IMG_1277.jpg

IMG_1275.jpg

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35 minutes ago, JFS said:

Thanks Neil

Here are some pics, cant get inside because I have some pots in there now.

Not sure of max temp rating? How would I find that out?

Jim

Usually it says max temp on the serial plate. Since yours doesn't, we can make some assumptions based on the size of the kiln and the amperage draw. What are the interior dimensions (hxw)?

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1 hour ago, JFS said:

Thanks Neil

Here are some pics, cant get inside because I have some pots in there now.

Not sure of max temp rating? How would I find that out?

Jim

IMG_1275.jpg

Analog pyrometer powered by the thermo couple? Sensitive device that has a big gash in the lower left corner. Definitely check with a good thermocouple but it may have seen its’ better day. If when firing And it sticks at 1200 a couple well weighted  finger taps often gets it past the sticky location.

Edited by Bill Kielb

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First, that pyrometer has nothing to do with the firing. It's just there to show what's going on in the kiln. Those old analog pyros are notoriously inaccurate, and yours is pretty beat up, and the thermocouple wire looks like it got burned. I'd toss the whole thing, and buy a cheap digital pyrometer.

Modern kilns that are 23w x 18h and rated to cone 10 pull about 39 amps. Paragon makes one that's 23x23 that is rated to cone 10 at 40 amps, with 3" thick brick. Yours only pulls 37 amps, so I'd bet it is rated to about cone 8, which is doable if you're going to fire to cone 6 for glaze. You'll have to change out your elements more often than if it were rate to cone 10.

Ideally we need to know the element resistance for your kiln to see if the elements are worn. You could call Euclids.com and see if they have any information on it, like max temp and element resistance. They can also make elements for you. The Ceramic Shop also shows elements for that kiln, you could call them and see if they know the element resistance. If you're comfortable with a multi meter and live electricity, you could also test the amperage draw when the kiln is on to see if it's pulling the full 37 amps or not.

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Neil summed it very well-if you get a cheap digital pyrometer mount it away from kiln not on kiln as yours is-Its to close to the heat. The thermocouple has a wire just like your burnt one and have that wire loose and plug it into the digital meter near the kiln but not mounted on kiln.. Keep the wire away from the spy plugs ot the lid. The digital meter will be about 100 times more accurate than what you have -they are under 60$ if you shop around .

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Hi JFS,

You might set cones on each shelf to get an idea how each level did. If you're able to see the cones through the peep holes, that can help you as well (be sure to wear eye protection - the infrared will hurt your eyes, and there's always chance of something going "ping" at just the wrong time - eye protection!); however, given your pyrometer provides consistent/repeatable feedback, once you've seen your cones after firing is complete and check your firing notes a few times, you'll be dialed in.

Taking notes can be helpful (tip from former owner of my ancient kiln), times, temperatures, control settings, cone indications, results...

How did your pieces come out? Did the glazes melt?

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jim, your photo shows the lid of the kiln open so far that i wonder if it could possibly get to temperature at all.   did you fire it that way or did you just prop it open to cool the fired pots?   

neither of those things are good.    

i do prop my lid only until the temperature reaches about 1100 F.  my prop is only 1/2 inch high, a piece of broken brick that i flick out of the way with a steel rod while briefly holding the lid weight off of it.   the very hot piece of broken brick lands on a dirt floor so it is ok.

you should not open your kiln until it is cool.  cool enough for you to touch it and whatever is in it without gloves.   opening it while it is hot and propping it the way it is in the photo can cause serious problems.   they have been discussed here by many people.

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19 hours ago, JFS said:

I have fired a few bisque fires to Cone 06 and the cone has fatigued tripping the switch successfully but the pyrometer only read about 1200 F at its max.

Forgive me if I'm talking down. You mentioned you just got the kiln and I am assuming this is all new to you.

If it tripped an 06 cone (1800+) then the meters wrong and it got to 1800-1825 depending on ramp, not 1200. I would just run a light test load with cone packs and see whats your kilns firing to without a doubt and toss the old meter. Maybe run some glaze experiments on some quickly thrown pots so you have something useful if the kiln does hit temp.

Normally you would put a pack of one cone lower, one dead on and one higher ( 5, 6 & 7 for cone 6 for example) but you might want to put some lower range ones so you can zero in if it fails to hit the lowest one. If the elements are shot then it might not get to cone 6 or even 5. Not sure if 11 hours is long enough to wait with your kiln or not, maybe wait 13, 14 and then give up and evaluate you cones. If a cone is bent half over then it hit that temp in heat work, The vent or propped lid, any hold or candle time and when you clicked through the knobs I think all play into that and since you have never done a glaze firing with this kiln you don't know your kiln and how long it should take. Start a log so you can track how/what its doing. If you do this and start having some glaze issues it will help a lot and it also will show you if over time the elements are starting to go and it is having trouble reaching temp. If that's the problem now and you need to change elements then the new elements will prob last around 100-150 bisque/glaze firings but some people get a lot more and some less so the log will help you dial it in.

 

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Thank you everyone for responses...

I am a novice so any criticisms are welcome! Not concerned about talking down, I am looking up... 

The lid was propped open while on Low for 1 hour and Med for 1 hour, then closed and switched to high (all three dials moving together). In hopes to get all water out of kiln

I dont have any glazes set up yet, so I did a Black Iron Oxide wash on some pieces and left some other pieces naked (Primitive techniques appeal to me!). So those pieces fired to some unknown temperature and look cool, I am easy to please! Will use them for planters

I took a liking to pottery because I dont have to have a , pencil, paper, tape measure, etc. That way it doesnt feel like work! But I understand the firing end of things requires some accounting, so I will get a log going.

Here are some pics of the inside of kiln:

IMG_1281.jpg

IMG_1282.jpg

IMG_1283.jpg

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10 minutes ago, JFS said:

so I will get a log going.

ha ha, get that. Hey just tape a piece of paper on the wall by kiln (not too close :-) and just date at line when you fire and jot down bisque or glaze and firing time. Only need more if you do something different such as long hold or fast fire.  Setting up cone packs can be a bit of a bother and I admit we only do it about half the time these days but it really does help to know exactly what each shelf fired to if you are trying to figure out certain glaze issues. Packed or loose will effect the temp on a shelf and some just fire differently from top shelf to bottom shelf. Once you know the kiln you can then pack accordingly for best results. Some people just do it occasionally or if they are in the situation you are in now. In any event they will get to the bottom of what the kilns doing so you know your next move.

Hey nice pots!

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There's really no need to prop the lid at all unless you know your pots are still wet. Even then you should close it once you get onto Medium. Otherwise you're just wasting electricity and needlessly extending the firing time. Always leave the top peep hole open. Unless you have a downdraft vent, in which case keep all the peeps closed and don't worry about propping the lid at all.

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Weigh the pots for dry. A day or 2 with no weight loss and you're good to go. Haven't blown anything up yet, either will you!

Nice pots for sure!

My manual electric would take 16 hours to evenly get 6. Let her ride!

There isn't much machinery out there as reliable as a kiln sitter, provided it's set up and gauged correctly.

Did I mention I like those pots!

Where can a fella buy one?

 

Sorce

 

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