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JeanWW

Test firing my new kiln

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Just setting up a little pottery studio at home and have bought a brand new kiln from Potclays.  (I'm in UK.)  The instructions are sadly inadequate and Potclays have not been very helpful so far.  I wondered if someone here could help me more quickly as I'm keen to do my first test firing.  

They have sent me some 06 test cones.  For the first test, they tell me to fire the kiln to take 5 hours to reach 750 degrees C.  Once it reaches 700 (after 4 3/4 hours), they say I should check the cone at 15 minute intervals.  They do not say what I am checking for.  I have asked them but they have not given me a clear answer.

For the second test, they say I should repeat the procedure but firing to 1000 degrees C.  For this firing they say the cone should bend tip to base.

What I don't understand is: if the cone bends right over at 1000 degrees C, what will the same cone do at 750 degrees C?  I need to know what I'm checking for; otherwise there's no point in checking.

Please help!

 

 

 

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First, what type of cones do you have- small, large, or self supporting?

If the cone bends at 1000C, it won't do anything at 750C. But the kiln may be climbing quickly at that point, so it's good to check it every 15 minutes to make sure you don't overshoot the peak temp. I also don't understand why you need to do 2 test firings. One will do the job just fine. Does the kiln have a sitter? Is this a manual kiln or digital? If it's digital, run it on a slow setting to cone 06, with a 3 hour preheat. If it's manual, run the bottom switch on low for 3 hours with the lid propped to preheat. Then close the lid, turn the other switches to low for 3 hours, then medium for 3 hours, then high till the cone bends and hits the shelf. First firings should go slow like that. For regular firings you can go 1-2 hours per setting. 

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Hi Neil

Thanks for replying.  The cones are small.  The kiln has a digital controller.  

The instructions say I should do the first test firing empty and the second test should be a bisque firing.   So I guess the second firing is more like a regular firing.

As I thought, the cone will do nothing at 750C, so I guess I would be checking to see that it is doing nothing.

So you advise me to do the first firing at 1000C instead of 750C?  This seems to make sense if I am using cone 06.  Should I put all the kiln furniture in, and put batt wash on the shelves beforehand?

I'm getting excited now and want to get going tomorrow!

 

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2 hours ago, neilestrick said:

Small cones only work in kiln sitters. You can't use them as a shelf cone. Just do an empty firing to cone 06 or hotter on slow with a 3 hour preheat and you'll be good to go.

Neil,  

What is your reasoning for not using small cones as a "shelf cone"?   

LT

Edited by Magnolia Mud Research

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1 hour ago, Magnolia Mud Research said:

Neil,  

What is your reasoning for not using small cones as a "shelf cone"?   

LT

Small cones are made to be used in sitters, not as a shelf cone. Large cones are made for sitting on the shelf.

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Neil,
Thanks.
 
Just wondering why you recommend not using them.
 
When I got a doll kiln with kiln sitter (~2007) for testing I did not have little cones. 
Contacted Orton, and the representative told me that the little cones are the same composition as big cones.
The person I spoke with said to cut the tip off a big cone to use in place of a little cone until I acquired little one. 

Orton also sells wire stands for holding the little cones at the proper angle relative to the kiln shelf.
I now use little cones in the sitter and in cone packs on each shelf when I use the test kiln.  
The little cones in the cone packs work just as well as the larger cones in my experience in my kiln.
 
I have used both large and small cones embedded side by side in the clay body as parts of sculptural items; fired in the school studio gas  kilns both cones fall simultaneously.
 
LT
 
 

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I was told by Orton a long time ago that small cones were not accurate for shelf cones, that only large cones should be used. I guess they're giving out different info. I also think that, due to their size, it's easy to set small cones at the wrong angle, or embed them too deeply into clay packs.

From Orton: While not recommended, Orton Small Cones can also be used on the kiln shelf in place of larger cones. Because they are smaller, higher temperatures and more heat are required for them to bend.

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thank you both, because i make very flat things,  i do not have room for the taller cones so i  have not used any for years.  i had also heard that small cones were not a good choice for shelf cones.  now i can use them again!:D

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I've found a lot of detailed advice on this at https://www.ortonceramic.com/files/2676/File/cones-and-firing-booklet.pdf

Still feeling a bit puzzled that the manufacturer of my new kiln said to fire up to 750C and use cone 06, but your advice makes more sense.  Not quite ready to go, as I've ordered some goggles for looking at the cone, but hopefully very soon!

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12 hours ago, oldlady said:

thank you both, because i make very flat things,  i do not have room for the taller cones so i  have not used any for years.  i had also heard that small cones were not a good choice for shelf cones.  now i can use them again!:D

From Orton: While not recommended....

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On 3/10/2018 at 10:43 AM, JeanWW said:

The instructions are sadly inadequate

Are the instructions on pages 3 and 4 of this what you have? With a brand new kiln I would do a very slow first firing to bisque temperatures plus a very long soak at the end, I would also leave the peephole plugs out for the entire firing if you are not using a kiln vent. You can verify temperatures with cones when doing this firing, just do it when the kiln is approaching your target temp / cone. I would also put your cone pack on a waster scrap of clay if you do a very prolonged soak.

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Hi Min

Yes they are the instructions.   Thanks for your advice.

I managed to get a sensible - and immediate - reply to this and some other queries by contacting Potclays through facebook messenger (I was using email and getting no response).  They do say: " With most modern controllers the cone test is largely redundant".   So it seems I have been worrying about nothing.  I have suggested that they rewrite the instructions.

 

 

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38 minutes ago, claygram said:

i do not have a "modern controller"  but what if something goes wrong with it or you set it wrong by mistake -- or does that not ever happen?

It's kind of hard to mess up, especially for an empty load, they are very descriptive.

I guess the most likely blunder is putting in 6 when you meant 06 and that would of course trash low fire glaze or screw up a bisque fire. The reverse seems less likely. I did one time put a 20 hour hold instead of a 20 minute. Always monitor the shutdown so had to kill power instead of the slow ramp down to 1200 that was programmed, so there's that. Load was fine but since it was the night before a show I was pretty worried until I could open the next morning and check. With a cone of heat work  an hour it obviously would have been a disaster if I had not been monitoring it.

I always use kiln packs so if there is an issue I know exactly what the load fired to not just what it was programmed for.     

Edited by Stephen

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