Duncan Teachers Plus 1100 degrees after 12 hours

[Eagleangel]

Sorry if there is a similar thread already… I’m new to firing full stop! I just purchased a Duncan Teachers Plus and was running a high fire test today.

 I started at 10am this morning on Manual setting, High Fire and set it for 6.5 hours with no idea how long it should take. I only have two glazed items in there just for the sake of it and placed cones 9 and 10 on the bottom and top shelves so they are visible from the peep holes.

After 11.5 hours and the cones are still standing.  I placed a thermocouple in the top a little while ago and it was reading 1111 degrees.  Half an hour later it was 1100 - I assume because the temp has dropped outside as well. 

I wonder if there is something or multiple things that I should have done differently? 

Maybe I should just use it to bisque if it won’t go higher? 

Thanks in advance…

 

Edited August 7, 2022 by Eagleangel

[Bill Kielb]

7 hours ago, Eagleangel said:

I only have two glazed items in there just for the sake of it and placed cones 9 and 10 on the bottom and top shelves so they are visible from the peep holes.

Yes, definitely search the forum, references to manuals etc… are many for this kiln. Just something to note, electric kilns rated cone 10 will only make it to that temperature a handful of times with very new elements. Most folks buy a cone ten kiln so they can get about 150 firings at cone 6. In general, Electric kilns and cone 10 work are not the best combination for sure. An old used cone 10 kiln with used elements probably will not make cone 10. 1100 degrees is a long way off so likely part of that kiln is not firing as well. Troubleshooting by measuring element resistances are likely the first best test. Please disconnect the power first!

Edited August 7, 2022 by Bill Kielb

[neilestrick]

Are we talking Celsius?

What's the max temp rating for that kiln? Some models are only rated to cone 8.

[Eagleangel]

Yes we are talking Celsius… reading the manual before hand suggested that it would indeed fire to cone 10.  
I opened the lid this morning and the two items actually look pretty good regardless. I would assume because it didn’t reach the 1260 mark that the same strength would not have been achieved

I will post some photos later when I get home. 
It has also been suggested (by another source) that I just didn’t let it go long enough and that the temperature goes up really slowly when at higher temperatures. 

[Bill Kielb]

Cone 02 is 1100c, cone 10 is 1285 c. A long way actually. In 11.5 hours it did not reach cone 04 with no load inside. I hope I am wrong but again an old cone 10 rated kiln with old elements and even almost no load inside still not making cone 10 is probably not gonna work for the reasons expressed previously above.

Edited August 8, 2022 by Bill Kielb

[Eagleangel]

I opened it up this afternoon to find that both items that I had in there were fine.  Maybe the temperature reading was incorrect and my placement of cones was incorrect… if would appear that the required temp of 1250 minimum for the white glaze was reached for the glaze to mature the way it did? 
I have ordered new parts for the kiln sitter as one of the little metal pieces was missing so will keep tinkering with it.  Even if I only use it to bisque, I think it will be worth it.

Thanks for your replies. 

[Bill Kielb]

Interesting that the glaze is melted at all. I assume your cone 10 witness cones did not budge. Maybe you are firing low fire (cone 04) products? I would suggest you double check.

Edited August 8, 2022 by Bill Kielb

[neilestrick]

A cone 10 glaze fired to cone 04 should still be chalky and dry. Double check your glaze. Also, I do not recommend using wire stilts at anything above low fire temps, as they tend to soften and bend.

[Eagleangel]

On 8/8/2022 at 9:19 PM, Bill Kielb said:

Interesting that the glaze is melted at all. I assume your cone 10 witness cones did not budge. Maybe you are firing low fire (cone 04) products? I would suggest you double check.

Thanks Bill, I have since learned that I did not have the cones positioned correctly so not sure if that was the reason they didn’t budge or a combination of that and temperature.
 

The glaze is a cesco opaque white 1260-1300 Celsius.   The stilts were fine this time, I have some of the ceramic ones as well… do you think they would be ok at high temps? 
 

I got some replacement cone supports and did a bisque with an 04 cone and it worked but I forgot to put the witness cones in as well.  So will make sure I do so next time!