Help with using a Duncan Automatic Teacher-Plus Kiln

[neilestrick]

On 7/29/2020 at 12:16 PM, K S said:

I really like my Duncan Teacher Plus.  Question: For bisque and glaze firing, I start the switch at the 10:00 position, even though no markings are there. I turn the switch to 8:00 position two hours later, 6:00 position two hours later, etc. I keep the toggle at Low Manual. My witness cones from the top, middle and bottom shelves are all the same. Sometimes I do a drop hold on a glaze firing to heal pinholes. Do any of you have a better firing schedule?

A very common firing schedule is 1 hour on low, 1 hour on medium, then high till the cone drops.

[Catatonic]

I'm a newbie potter and recently purchased my own Duncan teacher plus kiln secondhand from a guy who repairs kilns, so I was glad to get directed to an owner's manual on this thread. I tried the link but it's no longer working--I get that 404 message: essentially an internet dead-end, and Paragon is currently not answering the phone due to COVID.  So I decided to wing it by doing a series of test fires and logging what happens. BTW my kiln doesn't have that toggle switch at the bottom--just a dial that turns counter clockwise with three settings:  Over-glaze, Ceramic and Hi-Fire.  Guy who sold the kiln told me--incorrectly as it happens--that I was supposed to bisque fire at the same cone as the clay; so Cone 5 clay needed a Cone 5 bisque cycle. (Good thing I double checked with an actual potter!)  Without a manual I had no idea which setting to use for bisque firing, so I put it on Ceramic, used an 06 bar, set up two shelves, threw a few shards of green-ware all over them, and put an 06 witness cone on each one to see what would happen.  The kiln switched off in just over 4 hours, bar was sharply bent, top witness cone looks like a tired elephant, lower witness cone has a good arch but dips a little low (I had set them on potsherds).  So, I am guessing I needed to use the overglaze setting to do a bisque firing.  Good news is it DID hit cone 06 with no difficulty, and my pieces were properly cooked even if the final temperature seems to have been a bit higher than planned (possibly heated up too quickly? Any thoughts on this?) 

So, one other question I have about this model. Since it's technically automatic, I'm particularly interested in learning whether its possible to play around with firing routines. Has anyone ever changed a setting mid-firing? I mean, I wonder if it is wise, or possible, to start at a Hi-Fire setting, and partway through switch to a lower setting to get the effect of a "hold" such as you might have on a programmable kiln. I don't want to experiment with that kind of thing if it will do damage, but I would be interested if you, Neil Estrick, might have some ideas about what kind of flexibility can be had with this kind of kiln.

Edited December 11, 2020 by Catatonic
Wanted to add a question.

[Bill Kielb]

43 minutes ago, Catatonic said:

So, one other question I have about this model. Since it's technically automatic, I'm particularly interested in learning whether its possible to play around with firing routines. Has anyone ever changed a setting mid-firing?

Your manual https://216.198.210.227/files/manuals/LX_914_Duncan_Kiln_Owners_Manual.pdf this link should work. You may have to accept going to a non secure site. This is the old non https compliant site.

basically for bisque, time is needed to burn out organics which means a slow firing (200 degrees per hour) of about 9-12 hours. On automatic set to low and start. First two hours is auto then reverts to infinite switch knob setting. You may need to manually raise this as time goes on to finish in 9-12 hours. Page 13 lowest setting is overglaze then ceramic then high fire. Think of it as Low, Medium, High actually and it should make more sense.

Edited December 11, 2020 by Bill Kielb

[liambesaw]

All the knob for "overglaze, ceramic, hi fire" does is set an intermittent timer.  A super expensive timer to boot.  I have helped two people get these working and both had a bad timer.  Seems like people use the kiln until the timer fails, and then sell it on Craigslist and pretend it works.

Anyway, think of that knob as firing rate, and from what I remember, duncan wants you to use the ceramic setting for bisque and stoneware glaze firings and the hifire one for porcelain glaze firings.

The end temperature is determined by the kilnsitter.  I wonder if what he meant is to use the same setting for bisque and glaze, not the same cone. 

Edited December 11, 2020 by liambesaw

[Catatonic]

On 8/13/2018 at 1:46 PM, oldlady said:

 

 

On 12/10/2020 at 7:40 PM, liambesaw said:

The end temperature is determined by the kilnsitter.  I wonder if what he meant is to use the same setting for bisque and glaze, not the same cone. 

Might be what he meant but I think I saw a similar thing in the kiln manual referring to cone; will need to look again to make sure. Could it be they are referring to a biscuit fire instead of a bisque? I am only learning the difference in those terms from watching the Washington Street Studios YouTube channel--they go into a lot of history as well as chemistry and physics. I guess these days most people fire low for bisque and higher for glaze; apparently a biscuit fire does the opposite--higher for bisque than for glaze. Not sure why things are done differently now--new glaze technology, perhaps? 

Just did another bisque test, this time with cone packs in three areas (2.5 shelves stacked 5-6 inches apart) and partially loaded with a few pots on each level. I used 06 witness cones and guard cones at 05 and 04. It reached cone 06 in just under 5 hours (my first firing in empty kiln it was around 4.5 hours).  This time my 06 witness cone on bottom shelf at the center looked like a decent optimal burn--nice arch--and the 05 cone and 04 guard cones looked factory new.  The 06 cone on the edge of the bottom shelf (opposite the sitter) looked tired and droopy and the 05 guard cone had a slight lean to it; 04 looked untouched. Middle shelf had 06 cone quite overdone (reposing elephant pose) and the 05 cone had definite lean to it of about 15 degrees. Of course I forgot to put the cone pack on the upper half shelf!  

So although it's reaching temperature, it's doing it pretty quickly and its just a bit hotter than target in most places--ie, the outer edges of the shelves and on the higher ones (makes sense I guess).  Should I be concerned about the speed? The pots seem to be okay.

[liambesaw]

Yes that's too fast for bisquing.  Does your kiln not have high/med/low switches?

As far as biscuit firing, you only would do that for low fire earthenware.  They are bisqued as 04 and glazed at 06.  The body is still absorbent at both temperatures so glazing is not an issue.  If you bisqued to cone 5 it would be impossible to glaze because the clay is no longer absorbent.

[Bill Kielb]

19 minutes ago, Catatonic said:

So although it's reaching temperature, it's doing it pretty quickly

Go slower! Bisque fires or any form of them (biscuit?) are done slowwwwwwww to burn out organics. Figure out how to go slower by turning the power down. Going slower will also be more even throughout the kiln.  Bisque fires - get yourself to 9-10 hours. Glaze fires, about 7-8 hours each to start.

Glaze fire your clay to it’s maturity and use a matching cone glaze.

Edited December 16, 2020 by Bill Kielb

[Catatonic]

33 minutes ago, Bill Kielb said:

Go slower! Bisque fires or any form of them (biscuit?) are done slowwwwwwww to burn out organics. Figure out how to go slower by turning the power down. Going slower will also be more even throughout the kiln.  Bisque fires - get yourself to 9-10 hours. Glaze fires, about 7-8 hours each to start.

Glaze fire your clay to it’s maturity and use a matching cone glaze.

Guess I'd better call my kiln guy and find out if there's a way to slow it down.  There are only three settings (overglaze, ceramic and Hi-Fire) and there's no apparent way to adjust the firing aside from that.  Maybe I need to use the overglaze setting, which is normally meant for earthenware.  In these tests I've been using the ceramic setting.  Though its called an automatic kiln, the only automatic thing about it is the firing setting; the timer on this kiln is only a fail-safe shut off, little more than an egg timer, and the kiln doesn't have the manual option switch that other Teacher Plus kilns have.  At this point, I think my saving grace has been that the pieces I've fired thus far have been drying literally for months. But if I'm not getting rid of all the organics then I do have a problem, don't I?

Edited December 16, 2020 by Catatonic
adding stuff and rearranging

[neilestrick]

@Catatonic The switch is just an infinite switch. According to the Duncan manual, when you turn it on, it will go on low for 2 hours, then switch over to whatever cycle you've set the dial to. Overglaze is like medium, Ceramic is like med-high, High Fire is full on. Try this: start with the switch off, push the power button on the sitter, turn the switch to Overglaze and let it go 4 hours, then switch to Ceramic for 4 hours, then to High Fire until it's done. It may shut off on the ceramic setting.

[Catatonic]

10 hours ago, neilestrick said:

@Catatonic The switch is just an infinite switch. According to the Duncan manual, when you turn it on, it will go on low for 2 hours, then switch over to whatever cycle you've set the dial to. Overglaze is like medium, Ceramic is like med-high, High Fire is full on. Try this: start with the switch off, push the power button on the sitter, turn the switch to Overglaze and let it go 4 hours, then switch to Ceramic for 4 hours, then to High Fire until it's done. It may shut off on the ceramic setting.

Are you talking about the dial that sets the firing cycle when you say to start with the switch off? Because there is no other switch. I've attached a photo to illustrate.  If you aren't referring to the manual/automatic toggle switch that other Teacher Plus kilns have (which mine does not) then would you say its okay to change the setting in the middle of a  firing cycle?  ( I am half expecting you to say, "Hmmmmm....that's weird. Never seen one like THAT before!)

Edited December 17, 2020 by Catatonic

[Bill Kielb]

Yes, the big dial that says overglaze, ceramic, high fire according to the manual acts as a low, medium, high dial. Automatic I believe gets you two hours of an alternating on/off interval firing to slow down your initial firing temperature rise. This was an early attempt to semi automate drying things out slowly. Leave this knob (the big knob) on the lowest setting initially and turn it up gradually so maybe 3 hours on the lowest setting (overglaze) then two hours on medium (ceramic) , then the remaining on high. You only have a single knob so all the elements that can be controlled are controlled by that knob.  It’s a little backwards  or counter intuitive from what you might expect. If three hours on low is still too fast, then four  hours on low etc......

Edited December 17, 2020 by Bill Kielb

[Catatonic]

Awesome! Thanks so much for helping me chase this down! Will fire it up again in a few days when a few more pots are ready, and will keep you posted.

One last question. The pots I fired before-- would it be advisable to fire them again to ensure all the organics have burned off, or should I let them be? Would they perhaps get too hardened if bisqued again?

Edited December 17, 2020 by Catatonic
BECAUSE I NEVER THINK OF EVERYTHING I WANT TO SAY ALL AT ONCE!!!!

[neilestrick]

9 hours ago, Catatonic said:

Are you talking about the dial that sets the firing cycle when you say to start with the switch off? Because there is no other switch. I've attached a photo to illustrate.  If you aren't referring to the manual/automatic toggle switch that other Teacher Plus kilns have (which mine does not) then would you say its okay to change the setting in the middle of a  firing cycle?  ( I am half expecting you to say, "Hmmmmm....that's weird. Never seen one like THAT before!)

 

The switch isn't really setting firing profiles like a digital controller would. It's just a regular manual infinite switch that they've labeled as though it were an actual controller. At each setting it's going to cycle the elements on and off at a different rate to control how hot the kiln can get at each setting. The Overglaze setting is roughly the same as putting it the switch on medium, and since overglazes fire at such a low temperature it'll get hot enough on medium to do the job. The Ceramics setting is like medium-high, and will allow the kiln to get hot enough for low fire work. The High-Fire setting is full on, which is needed for cone 6 work. They way they tell you to fire it is to just put it on one of those settings, which means it goes on low for two hours and then jumps up to the setting. We don't generally fire our kilns like that, though, because it fires too quickly that way. Instead, we go through a series of turn-ups to increase the temperature slowly so that we don't harm our pots by heating too quickly or getting incomplete burnout or melting the glazes too fast. So ignore the labels on the switch and instead think of it as low to high, and do a series of turnups.

[Catatonic]

That is really helpful--thanks! As a newbie I haven't really had any idea of how a kiln like mine functions--there was no label with arrows saying, "This is how you bisque!"  ;0)

[Bill Kielb]

12 hours ago, Catatonic said:

One last question. The pots I fired before-- would it be advisable to fire them again to ensure all the organics have burned off, or should I let them be? Would they perhaps get too hardened if bisqued again?

cone 5/6/10
You should be able to re-bisque them. Bisque temperatures generally only sinter clay which is not really melting it.

[Mark C.]

Are these kilns made only for  The Plus teachers?? Maybe thats a new cert level? 

[Catatonic]

3 hours ago, Mark C. said:

Are these kilns made only for  The Plus teachers?? Maybe thats a new cert level? 

If so, I am definitely in possession of contraband!

[Bill Kielb]

@Mark C.

I think they wanted to make every firing a learning experience or teachable moment as we say.

Edited December 19, 2020 by Bill Kielb

[Mark C.]

3 hours ago, Bill Kielb said:

@Mark C.

I think they wanted to make every firing a learning experience or teachable moment as we say.

A plus moment sound more like a hallmark greeting card. I guess now with automation  controls all that is behind us. 

[Catatonic]

2 hours ago, Mark C. said:

A plus moment sound more like a hallmark greeting card. I guess now with automation  controls all that is behind us. 

Unless you're like me and picking up the kilns people abandon when they upgrade to those fancy new Skutts!

[JohnS]

Hey, sorry to jump in on this topic but it's exactly the same issue I'm having. I've just had one of these hooked up and am almost ready to start firing some stuff (total newbie) and have been trying to make sense of the manual with regards to settings and what cones to use. 

I asked someone on reddit what setting for bisque and they said overglaze, then ceramic for glaze and hi-fire was for cone 8-10. Whether that's actually true I'm not sure as I've not tested it yet.  The manual seems to suggest that you shouldn't need to change between the three like what's been kindly suggested so far (I'm hoping that's not the case and it is as simple as turning it on and letting it cook!).  Can anyone confirm yet what the actual process is? 

Also, with regards to what cone to use, right at the start of these comments the OP said that the previous owner said to bisque at cone 5, now, I know that you're supposed to generally bisque in the 05 region, but the manual does actually say for stoneware using an orton sitter cone to use 7-9 for both bisque and glaze.  This has completely thrown me. 

 

I've yet to order my cones due to this, so I can't confirm, well, anything! Anyone got any advice? 

 

Cheers

John 

Edited December 28, 2020 by JohnS

[Bill Kielb]

Cone 04 -06 for bisque to sinter midfire clay so you can glaze and handle it. Slow bisque firing about 200 deg. f per hour or let’s say 8-12 hours to completely burnout organics. And slowly dry things out in the beginning of the firing so from room temp to 200 f go slow for an hour or two. In other words what you read above is likely the only way to get this done. I wish they would have named it semi automatic kiln actually. That’s my experience.

Edited December 29, 2020 by Bill Kielb

[liambesaw]

The overglaze-ceramic-hi-fire knob is an adjustable interval timer.  At overglaze it slowly ramps to full power, at ceramic it has a medium ramp and hi-fire is a steep ramp.  

And it's one of those parts where if it goes out, its gonna cost you about 400 bucks.  Unfortunately it's not an off-the-shelf part, it's a mechanical timer made for this kiln and available from duncan(paragon?)

[neilestrick]

50 minutes ago, liambesaw said:

The overglaze-ceramic-hi-fire knob is an adjustable interval timer.  At overglaze it slowly ramps to full power, at ceramic it has a medium ramp and hi-fire is a steep ramp.  

And it's one of those parts where if it goes out, its gonna cost you about 400 bucks.  Unfortunately it's not an off-the-shelf part, it's a mechanical timer made for this kiln and available from duncan(paragon?)

The original rotary switch was the KM300. The replacement is the SW6, which is $48. The other part in that system is an interval delay timer, what paragon calls a 2 in 1 timer on their wiring diagrams, and it only seems to exist on the DA models, not the EA models. I believe the DA models have the Manual/Automatic switch, and the 2 in 1 timer is wired to that. I think the 2 in 1 is what keeps it on low for 2 hours before it allows the rotary switch to take over and climb . From what I've found on the internet, the Ceramicraft.AU is the only place that mentions it, and says it's $400+ and only available from Paragon. I'm betting that Paragon doesn't actually make them any more since they officially stopped supporting Duncan kilns a couple of years ago. However the company that originally made the 2 in 1 timer, Artisan Controls, is still around and may be able to recommend a replacement. There are other interval timers made by Artisan in the Duncan EA models, and those are still available but cost $110+ each.

IMO, these Duncan kilns are not worth the cost of repairing them to original condition, especially since the systems don't seem to perform as well as they should. The simplest solution would be to wire all the elements directly to the power cord and plug it into a wall mounted digital controller. The other option would be to take out all the original controls and rewire them with typical lo-med-hi switches. Unfortunately, those solutions require either a good knowledge of kiln wiring or a fair amount of money.

[liambesaw]

I know someone who recently purchased the timer unit from paragon, so they had them up until at least 3 months ago.  It was expensive but they got the kiln in pretty much new shape so they didn't complain too much