Help with using a Duncan Automatic Teacher-Plus Kiln

[JohnS]

9 minutes ago, lauradeegee said:

Here's the toggle I have on mine

I tried something like this yesterday and it shut off in the 8:30 position, barely reached 4 hours. Very strange! Something else has to be wrong

Ah right, we have slightly different models so I can't speak as to what's best for that toggle. 

 

I know I made a rookie mistake of firing either not enough pieces or pieces that had been half fired before (because, like you, my firing was too quick). 

 

So certainly what worked for me was (and my kiln is just an automatic so I'm presuming the switch at the auto position might make it similar to mine) - 

 

Set it to auto

Stick in a shelf's worth of stuff

Make sure that both elements are heating up (my switch was bad and only the bottom element was working for me initially - there's another long thread about that) 

Use the firing schedule I posted in the previous comment and ignore the UNDERGLAZE HI FIRE settings etc. Just do it manually. 

Last time I did this it fired in about 9 hours to cone05 whereas before, using the predetermined UNDERGLAZE etc it did it in about 3 as well. I'm guessing that because these kilns are fairly old that the automatic part goes over time. 

Edit - everything is relevant to the flat bit under your dial equalling the direction of the arrow I.E. If the flat bit is at 12 o'clock then when you put the dial back on then the arrow should be at 12 o'clock as well. 

Let us know how you get on. 

Edited October 1, 2021 by JohnS

[lauradeegee]

Hi all!

I made a few more attempts with the same result - I did the "manual"  schedule that was suggested but still had very short firings. I was still worried that I has mistaken the position of "OFF" on my knob so I just tried again to turn the switch while observing the kiln to double check where "off" was. When I'm in the off position, the kiln still creates heat but the elements are much quieter than when I'm in any other position. As soon as I turn the knob at all, the elements get louder. I left the kiln in the off position and watched for a few minutes, and realized that the bottom elements were getting red hot very quickly.

Here is my new theory, maybe someone can let me know if it seems likely: There is a wiring issue with my kiln where no matter what position the knob is in,  the bottom set of elements is at full blast. That's why no matter what I do to try to control the timing of my firing, it always ends within 4 hours. 

Maybe there's something about electrical kilns that would explain away my theory, I'm curious if anyone has any thoughts Thank you as always! 

[JohnS]

7 minutes ago, lauradeegee said:

Hi all!

I made a few more attempts with the same result - I did the "manual"  schedule that was suggested but still had very short firings. I was still worried that I has mistaken the position of "OFF" on my knob so I just tried again to turn the switch while observing the kiln to double check where "off" was. When I'm in the off position, the kiln still creates heat but the elements are much quieter than when I'm in any other position. As soon as I turn the knob at all, the elements get louder. I left the kiln in the off position and watched for a few minutes, and realized that the bottom elements were getting red hot very quickly.

Here is my new theory, maybe someone can let me know if it seems likely: There is a wiring issue with my kiln where no matter what position the knob is in,  the bottom set of elements is at full blast. That's why no matter what I do to try to control the timing of my firing, it always ends within 4 hours. 

Maybe there's something about electrical kilns that would explain away my theory, I'm curious if anyone has any thoughts Thank you as always! 

A quick way to sort this out would be to buy a thermostatic "gun" from amazon.  Mark the clock face around the dial on the kiln and move from where you think is off anti clockwise measuring every 30 mins at each hour (when I did my test I measured every 30 mins and 1 hour at each hour to see if it was increasing). This should give you an idea. 

 

It might just be the case that yours is just going on or off and not stopping at the correct heat, or there could be something with the other switch that you have.  

 

Give the gun a go and mess around with the settings would be my advice to know once and for all. 

[Bill Kielb]

45 minutes ago, lauradeegee said:

Here is my new theory, maybe someone can let me know if it seems likely: There is a wiring issue with my kiln where no matter what position the knob is in,  the bottom set of elements is at full blast. That's why no matter what I do to try to control the timing of my firing, it always ends within 4 hours. 

Do you have an automatic / manual switch? If yes, in the manual mode the bottom elements will be on. In the auto mode the bottom elements will cycle on the built in interval timers. If the interval timers have failed closed then the bottom elements will stay on all the time. Question, in auto mode do the bottom elements  cycle on and off?

[Catatonic]

On 6/30/2021 at 4:13 PM, JohnS said:

That would be great thanks. 

 

Cheers for the answers. Might to try to give it another go tomorrow then. 

 

Cheers 

JohnS--its been a long time responding to this (oh my, has it already been four months??? I'm so sorry!) but I have finally (just now!) gotten a call from the guy who worked on my old Duncan (Peter Yang). Here's the weird situation with that... when I first used that kiln, the dial would click at each of the firing settings--once at 7 o' clock for Overglaze, once at 4 o' clock for Ceramic, once at 2 o' clock for Hi Fire and once at 12 o' clock for Off. It all lined up with the labels on the face of the kiln. But on the very day my elements went crazy, so did the dial: it no longer clicked at the Off position, but it would click at 11 o'clock, and at 10 o' clock and at 2 o'clock. Totally mysterious. When Peter did his test firings on the kiln to isolate why the new elements he put in weren't firing to temperature, he just dealt with it as it was--didn't worry about the clicks, but just used the arrow as his guide because it was installed correctly with the flat bit facing Off.  So that's the end of the story, I guess. He tells me that the original Duncan dial was installed right side up, but the later dials made by Paragon for the old Duncan kilns were to be installed upside down. The newest dials, apparently, are completely different and require a conversion kit. I don't know if this is any help at all, but there you have it. 

Cat

[lauradeegee]

On 10/18/2021 at 8:19 PM, Bill Kielb said:

Do you have an automatic / manual switch? If yes, in the manual mode the bottom elements will be on. In the auto mode the bottom elements will cycle on the built in interval timers. If the interval timers have failed closed then the bottom elements will stay on all the time. Question, in auto mode do the bottom elements  cycle on and off?

Oh thank you for mentioning this! I had been messing around with that switch when I was trying to troubleshoot and it was in manual mode when I noticed the bottom elements getting red hot. In auto mode the elements cycle on and off, including when the knob is in the off position. I guess next step is to measure the heat like John suggested!

[Bill Kielb]

43 minutes ago, lauradeegee said:

I had been messing around with that switch when I was trying to troubleshoot and it was in manual mode when I noticed the bottom elements getting red hot. In auto mode

So the slowest this thing will go is the switch set on auto and the top element switch in the off position. The bottom elements will cycle on the timer(s)  until after two hours they will go to full on and stay on till the end of firing. Meanwhile starting with  the top switch off (knob arrow pointing up to 12:00) and turning counterclockwise at the end of the two hours will be as slow as it can reasonably go. If that all works, then there is a procedure to calibrate the top switch which may reveal if it is just out of calibration or needs to be replaced.

[lauradeegee]

On 10/20/2021 at 11:22 AM, Bill Kielb said:

So the slowest this thing will go is the switch set on auto and the top element switch in the off position. The bottom elements will cycle on the timer(s)  until after two hours they will go to full on and stay on till the end of firing. Meanwhile starting with  the top switch off (knob arrow pointing up to 12:00) and turning counterclockwise at the end of the two hours will be as slow as it can reasonably go. If that all works, then there is a procedure to calibrate the top switch which may reveal if it is just out of calibration or needs to be replaced.

I tried this and was still only able to reach about 5 hours. I added some more ware to the kiln like JohnS suggested, then started at 12 o'clock, waited 2 hours, turned to 10 o'clock, waited 2 hours, turned to 830, and then it shut off after about an hour. Can you tell me about the procedure to calibrate the top switch?

[neilestrick]

Not trying to be a downer here, with a manual kiln, once it's on high it's on high and it's going to rocket to temp and there's nothing you can do about it at that point. It may be worth getting a pyrometer and seeing how fast it climbs on a medium setting. Maybe you just need to leave it there and let it slowly climb to extend the firing. For a bisque firing it may be that you never need to go to a higher setting than that.

One thing to remember with these old kilns is that we've come along way in how we think about firings. Back when Duncan was building kilns we were pretty much just concerned with it getting to temp, and slowing it down was only an issue at the low end so we didn't blow things up. Plus these kilns were marketed to schools, who preferred fast firings so the kiln wasn't running after the teacher went home for the day. Nowadays we put a lot more thought into what we do at the high end of a firing, because we've learned that poor burnout can be the cause of some glaze problems that we used to attribute to the glaze itself. There's only so much that can be done with a manual kiln, though, so trying to stick to firing schedules and specific rates of climb may be a wasted effort. Assuming everything on your kiln is working, you may just need to adjust your glazes or final temp to get the results you want. Or, budget permitting, get a wall-mounted digital controller to run the kiln with if you really want more control.  People have been firing manual kilns for decades with great success, though.

[lauradeegee]

Not a downer at all! I'm so new to this, so the wider perspective is really helpful, I think its what I need the most.  I was under the impression that these fast firings were basically incomplete firings that would cause my ware to be brittle or have some other structural issue. Your comment is giving me the impression that these pieces are fully bisque fired, and if I do a glaze firing, the glaze might not turn out the way I want, but the pieces will be complete and structurally fine,  am I understanding that correctly? 

Thank you so much! I feel so zoomed in on the timing and the knob etc, the context is so helpful 

[neilestrick]

1 hour ago, lauradeegee said:

Your comment is giving me the impression that these pieces are fully bisque fired, and if I do a glaze firing, the glaze might not turn out the way I want, but the pieces will be complete and structurally fine,  am I understanding that correctly? 

Correct. The only real issue with firing fast is that you may not get all the organic matter burned out during a bisque, which could cause glaze problems. But cone 04 is cone 04, no matter how fast you get there because cones measure heatwork, not temperature. If you're not having glaze problems then you're good to go.

[Bill Kielb]

4 hours ago, lauradeegee said:

I tried this and was still only able to reach about 5 hours. I added some more ware to the kiln like JohnS suggested, then started at 12 o'clock, waited 2 hours, turned to 10 o'clock, waited 2 hours, turned to 830, and then it shut off after about an hour

So empty I am guessing with the top switch off and only the bottom elements on you can get to some cone in five hours, but just turning the top switch to 10:00 reduces firing time a bunch. That would indicate the top switch is not ideal for sure so the calibration technique is below. 
Neil is correct as manual kilns are fine, and actually a five hour glaze firing is not really the end of the world quick. And actually if this has all been in an empty kiln thus far  it will go up considerably as the kiln is filled. Beyond that to extend bisque firings you could always prop the lid an inch or two for the first couple hours  as was customary back in the day.

Calibrating is not for everyone and if the switch is very far out, replacement is the only recourse as calibration has its limits. For now, propping the lid for the first couple hours then minimal top element may be more than adequate for regular firings.

[neilestrick]

I am not no longer clear as to which switches or how many switches or what each switch controls in each of the kilns in this thread, but something to keep in mind is that depending on which switch controls which elements, by putting switches on different settings you may cause the kiln to fire unevenly. The sitter only knows how hot it is right in the middle of the kiln where it's located, so just because it's hot enough in that area doesn't mean it's that hot throughout the top and bottom of the kiln, too.

[Bill Kielb]

1 hour ago, neilestrick said:

am not no longer clear as to which switches or how many switches or what each switch controls in each of the kilns in this thread, but

I think she has the single knob infinite switch which controls just the top elements. The auto / manual switch controls the bottom elements and cycles for two hours then goes to constant on in auto mode. Anyway, that’s the premise of her stuff which seems correct at this point. I really despise the creation of this kiln though, it confuses so many.

[Mark C.]

( It may be worth getting a pyrometer and seeing how fast it climbs on a medium setting. Maybe you just need to leave it there and let it slowly climb to extend the firing. For a bisque firing it may be that you never need to go to a higher setting than that.)

A digital pyrometer (cheap) is what need to see wahts going on really-you may have to drill a small hole in kiln but its no big deal to install one.

[neilestrick]

32 minutes ago, Bill Kielb said:

I think she has the single knob infinite switch which controls just the top elements. The auto / manual switch controls the bottom elements and cycles for two hours then goes to constant on in auto mode. Anyway, that’s the premise of her stuff which seems correct at this point. I really despise the creation of this kiln though, it confuses so many.

It's a horrible kiln in terms of ease of use, and there are several versions that are just dissimilar enough to make it even more confusing. I have ideas about how to make them more user-friendly and less expensive to maintain, but it's not stuff that someone without kiln repair knowledge can do, so at this point we just need to keep this thread going and hope that more and more people contribute to it as a knowledge base.

[Bill Kielb]

9 hours ago, neilestrick said:

I have ideas about how to make them more user-friendly and less expensive to maintain, but it's not stuff that someone without kiln repair knowledge can do, so

Change the timers / contactor arrangement out for a second infinite switch was the best one I think we advocated here and someone reasonably skilled executed it. Makes the kiln  truly old school, fairly economical and definitely controllable. At least one of the timers are extinct and ridiculously expensive to replace. Someone here did it once successfully as I recall.

[neilestrick]

4 hours ago, Bill Kielb said:

Change the timers / contactor arrangement out for a second infinite switch was the best one I think we advocated here and someone reasonably skilled executed it. Makes the kiln  truly old school, fairly economical and definitely controllable. At least one of the timers are extinct and ridiculously expensive to replace. Someone here did it once successfully as I recall.

Getting rid of all the timers and relays is a good thing. Simplify! My other thought is to replace the terminal bricks with Skutt terminal bricks, which are a close fit. They require a little bit of filing to lower the element groove at the corners, but they work. With those you could then use 6 elements that wrap twice instead of 12 elements that wrap once, which would lower element costs quite a bit and make sourcing elements a lot easier.

[Cara]

I am looking at two used Duncan Teacher kilns. What questions do I need to ask the seller? They were used a year ago and everything was fine. Can I use these for porcelain firing? I made dolls when I was young, as an apprentice, so some of the particulars were lost to time. Any help is appreciated! ~Cara

[neilestrick]

2 hours ago, Cara said:

I am looking at two used Duncan Teacher kilns. What questions do I need to ask the seller? They were used a year ago and everything was fine. Can I use these for porcelain firing? I made dolls when I was young, as an apprentice, so some of the particulars were lost to time. Any help is appreciated! ~Cara

Ask what voltage and phase of electrical service they're set up for. The serial plate should give you that information. It should also say the max temp rating of the kiln. If you plan to glaze fire to cone 5/6, you'll want a kiln that's rated for at least cone 8. Beyond that it's all about the condition of the kiln. Are the bricks in good condition? Are the lid and floor structurally sound and not cracked? Hairline cracks are normal, but big cracks are a problem.

[cshadduck]

I bought this same used kiln and I have no manual with it.. How can I get a manual to get a general idea how to work it?  Thanks!

 

[Bill Kielb]

Post your model number. This may help in general terms of firing: https://paragonweb.com/wp-content/uploads/LX_914_Duncan_Kiln_Owners_Manual.pdf

And this may help if your model contains an early form of automatic or semi automatic operation: https://paragonweb.com/wp-content/uploads/W-DA-1029-N-Theory.pdf

If you post the model, wattage, etc…. Others may have specific document references.

 

Edited January 9, 2022 by Bill Kielb

[cshadduck]

13 hours ago, Bill Kielb said:

Post your model number. This may help in general terms of firing: https://paragonweb.com/wp-content/uploads/LX_914_Duncan_Kiln_Owners_Manual.pdf

And this may help if your model contains an early form of automatic or semi automatic operation: https://paragonweb.com/wp-content/uploads/W-DA-1029-N-Theory.pdf

If you post the model, wattage, etc…. Others may have specific document references.

 

Gee, thanks for the quick response and downloads, Bill!   I am going to find the model # soon and post it in a day or so but this manual link is a great start for me!!  I am just starting wheel pottery as my hobby from a class at college and want to be pretty serious about it so thank you again.  cs

 

[cshadduck]

On 1/9/2022 at 12:36 PM, cshadduck said:

Gee, thanks for the quick response and downloads, Bill!   I am going to find the model # soon and post it in a day or so but this manual link is a great start for me!!  I am just starting wheel pottery as my hobby from a class at college and want to be pretty serious about it so thank you again.  cs

 

The kiln is a Duncan Automatic, The Teacher-Plus - Model # DA820-2 cone B..  I have no idea how to use my kiln as I got it second hand and it came with no instructions period.  Thank you for any help!

 

[Eagleangel]

I’m another newbie… I am about to purchase one of these.  Any hints or tips on a safe way to transport?