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#1 Nelly

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Posted 02 November 2012 - 07:38 PM

Dear All,

I am about to start a glaze firing.

While I normally do cone 6, tonight I want to try cone 7.

I have self-supporting cones and am using the Frog Pond Schedule. This is the schedule presented at NCEC by the man who runs Frog Pond Studio. Tucker's gave this to me as my working standard schedule for my cone art kiln.

So, let's start with the basic information on the Big Ceramic Store Cone chart.

Okay, so, you look across the chart:

I see:

7
2194 (27 degrees per hour) 2262 (108 degrees per hour) and then 2295 (270 degrees per hour)

I think I am firing in the middle. Am I reading this correctly? I have 6,7 and 8 in my bottom peep hole right now.

But I am wondering if you can tell me what temperature you fire to at cone 7?? How much can I play with these numbers??

I have noticed lately my glazes (i.e., matt black/white and saturated iron) are looking under fired. Thus, I want to go up a cone.

I remember someone said "if you don't know the answer go and wedge some clay" when a simple question like the stages of clay development were presented. I think, if I was to guess, this is a similar question to the stages of clay development. So please don't send me to wedge clay. Somehow I missed this lesson in the guzzillion classes I took to get to this point.

Can you, like the stock market, explain this chart in a really simple way.

I am still at the push and start stage using my computerized kiln. Tucker's said "just adjust the highest temperature on this basic Frog Pond schedule to what you want."

So, is it 2262?? Is that what I would want in F degrees?

If there is anyone out there who fires to cone 7, can you give me an "about" to what temperature you fire to?

Nelly

#2 Chris Campbell

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Posted 02 November 2012 - 09:09 PM

If you have a computerized kiln just program it to fire to Cone 7. This is the simplest solution if what you want is a true Cone 7 to see if your glaze will work better.
The technology that goes into their schedule program is very precise and will give you a solid 7 without the hassle of trying to figure it out beforehand then wonder afterwards if you did it right. If seven ends up being the right temp then you can start to tweak it.
Just my lazy bones opinion however! :P

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#3 Mark C.

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Posted 02 November 2012 - 09:14 PM

Nelly
heres the deal-you asked about-
2194 (27 degrees per hour) 2262 (108 degrees per hour) and then 2295 (270 degrees per hour)



What this means is at 27 degrees per hour on the ramp up-thats the how long it takes to gain temperature per hour the final temperature is 2194-this is a really slow climb
Its called heat work that is the faster it takes to get to a given temp the glaze will need more temp than say a slower rate for the glaze to melt or mature.
So if you really go fast up say 270 degrees per hour on the ramp up then cone 7 comes at 2295
The 2262 is a medium climb rate at 108 degrees per hour.
This should be easy with a new fangeled digital pyro.
The only way to really know how your glazes are with heat work is seeing a cone bend as this cone is just like your glaze and reacts the same as the heat work-thats why its important to have and use cones at least at some point. When you rely on say a digital pyrometer only and the element goes bad your whole fire will be off where as if you looked at a cone you can see this time temperature relationship thur the cone. This is my biggest beef with the use of only this instrument as it does not account for the time temperature heat work. Yes you can dial it with cones and then rely on the pyro for some time but sooner or later it will wear out and your fire will be cool or hot when the thermocouple gives out. I have seen at least 20 elements burn out in my life-but my atmospheres are far more corrosive. I have had several electric thermocouple give out as well as a few gauges-now its all digital.
As I have said to many when this happens and they only rely on the pyrometer -OH WELL cones they never go wrong.
Hope this helps
Mark
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#4 Nelly

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Posted 03 November 2012 - 12:48 AM

If you have a computerized kiln just program it to fire to Cone 7. This is the simplest solution if what you want is a true Cone 7 to see if your glaze will work better.
The technology that goes into their schedule program is very precise and will give you a solid 7 without the hassle of trying to figure it out beforehand then wonder afterwards if you did it right. If seven ends up being the right temp then you can start to tweak it.
Just my lazy bones opinion however! :P


Dear Chris,

The problem is that I think either I have to do some math to figure out a new ramp schedule. There is no button that says Cone 7. But you know, when I think about it, there is part of that programming schedule that does say cone #. Maybe that is where I should put the 7 in and then make sure my top temperature number is as high as I want it. You are right. I just figured it out. I can put a 7 where there is now a 6.

Sorry to everyone for another silly question but I had to ask.

Thank you again Chris.

Nelly

#5 JBaymore

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Posted 03 November 2012 - 09:34 AM

I think that maybe part of the issue is that cones do not measure temperature, but many potters seem to think that they do. Mark was already explaining this in his posting.

Cones measure the EFFECT on ceramic chemistry of heat energy applied over time. This is usually called "het work". We don't really care what the temperature is inside the kiln as to final firing effects... we care about what has happened to the wares in the kiln.

This is where the pioneering work of Herman Seger came in. He developed the chemical relationships that allowed the production of what we now call pyrometric cones (and our ability of analyze glazes a bit before we mix and test them). The cones are chemically designed to melt from a certain amount of heat energy applied to them over a certain amount of time. They behave exactly like the chemistry in the clay bodies and glazes, so the cones can accurately reflect what has happened to the clay and glaze.

To say that you have fired to "cone 7" (and here we likely are talking about ORTON cone 7....not Seger cone 7...they are different) tells us we have applied a certain amount of heat work to the clay and glaze. If you fire slowly, then the kiln will not have to get as hot by the peak of the firing as it would if you fired more quickly. Same "heat work" is done because it is a combination of temperature over time.

The kilns with the "cone fire" programs take into account the combination of temperature and time. They do not just program in an end point temperature... they also track the time factor to arrive at a solution.

Hope this helps build of Mark's information.

best,

...................john
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#6 Nelly

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Posted 03 November 2012 - 09:36 AM

Nelly
heres the deal-you asked about-
2194 (27 degrees per hour) 2262 (108 degrees per hour) and then 2295 (270 degrees per hour)



What this means is at 27 degrees per hour on the ramp up-thats the how long it takes to gain temperature per hour the final temperature is 2194-this is a really slow climb
Its called heat work that is the faster it takes to get to a given temp the glaze will need more temp than say a slower rate for the glaze to melt or mature.
So if you really go fast up say 270 degrees per hour on the ramp up then cone 7 comes at 2295
The 2262 is a medium climb rate at 108 degrees per hour.
This should be easy with a new fangeled digital pyro.
The only way to really know how your glazes are with heat work is seeing a cone bend as this cone is just like your glaze and reacts the same as the heat work-thats why its important to have and use cones at least at some point. We you rely on say a digital pyrometer only and the element goes bad your whole fire will be off where as if you looked at a cone you can see this time temperature relationship thur the cone. This is my biggest beef with the use of only this instrument as it does not account for the time temperature heat work. Yes you can dial it with cones and then rely on the pyro for some time but sooner or later it will wear out and your fire will be cool or hot when the thermocouple gives out. I have seen at least 20 elements burn out in my life-but my atmospheres are far more corrosive. I have had several electric thermocouple give out as well as a few gauges-now its all digital.
As I have said to many when this happens and they only rely on the pyrometer -OH WELL cones they never go wrong.
Hope this helps
Mark


Dear Mark,

Got it.

It is about ramping up and heat work.

If I translated your paragraph correctly, with my new machine it should be easy to go at speed required. Know that inside my kiln I have three thermocouples. One is the main pyrometer in the middle. The other two are close to the bottom and top shelf.

I do use cone packs. I have done no adjustment since buying the kiln. I have simply done what the kiln has given me without any real thought until now--when I need good results.

I did notice some dark shavings at the bottom under one pyrometer or thermocouple. I wonder if I have burnt off the coating and this is the issue?? I have not seen this with the others. I am guessing this could affect how the kiln senses heat??

Anyway, I will keep you posted on today's firing.

Thank you for the explanation of the cone chart. It looks simple enough but you really need to understand it to optimize your firing and this is definitely something not taught in a community college night class.

Nelly

#7 Nelly

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Posted 03 November 2012 - 10:15 AM

I think that maybe part of the issue is that cones do not measure temperature, but many potters seem to think that they do. Mark was already explaining this in his posting.

Cones measure the EFFECT on ceramic chemistry of heat energy applied over time. This is usually called "het work". We don't really care what the temperature is inside the kiln as to final firing effects... we care about what has happened to the wares in the kiln.

This is where the pioneering work of Herman Seger came in. He developed the chemical relationships that allowed the production of what we now call pyrometric cones (and our ability of analyze glazes a bit before we mix and test them). The cones are chemically designed to melt from a certain amount of heat energy applied to them over a certain amount of time. They behave exactly like the chemistry in the clay bodies and glazes, so the cones can accurately reflect what has happened to the clay and glaze.

To say that you have fired to "cone 7" (and here we likely are talking about ORTON cone 7....not Seger cone 7...they are different) tells us we have applied a certain amount of heat work to the clay and glaze. If you fire slowly, then the kiln will not have to get as hot by the peak of the firing as it would if you fired more quickly. Same "heat work" is done because it is a combination of temperature over time.

The kilns with the "cone fire" programs take into account the combination of temperature and time. They do not just program in an end point temperature... they also track the time factor to arrive at a solution.

Hope this helps build of Mark's information.

best,

...................john


Dear John,

Okay, let me see if I have this correct.

In my kiln right now, I have clay that has been bisqued. On top of the bisque is a glaze.

There are two types of cones that have been developed.

The miracle of these cones is that they measure how the temperature in the surrounding kiln is reacting to the clay body and the glaze on-top. The stuff these cones are made of helps us to simply see how our glaze and clay body is reacting at a certain temperature.

My glaze firing was to be 13 hours. I am guessing it went off before this time.

In addition, as the kiln gets hotter, heat work should take less time (because it has already been done).

Oh John, I do hope I am getting this right??

I remember in the old kilns I used, they chugged slowly through the final segments of firing. Mine seem to zoom through??

Anyway, I digress.

From your paragraph the key points I got were: 1) cones are important and 2) they measure how your clay and glaze react to each other under certain temperature conditions. It is not all about "heat work." The longer you study the cones in accordance with the temperature you are firing, the clay you are using and the glazes applied--the better off you will be.

Did I get this right??

Thank you for your response.

Nelly

#8 neilestrick

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Posted 03 November 2012 - 10:37 AM

Firing to a cone number is more accurate than a temperature. Cones measure heat work, which as the result of temperature over time. A slower climb in temperature will result in a lower temp when the cone melts than a fast climb.

Think of it like cooking a nice roast. You can cook it at 350 for an hour, or 275 for 3 hours. Either way you have a cooked roast. Lower temeperature for a longer time yields the same result as a higher temperature for a shorter time.

Cone charts show this effect. Slower climb (longer time) yields the same heat work at a lower temperature as a faster climb (shorter time) to a higher temperature. These rates of climb really only come into effect for the last 250 degrees or so of the firing.
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#9 JBaymore

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Posted 03 November 2012 - 05:41 PM

In addition, as the kiln gets hotter, heat work should take less time (because it has already been done).


It is not "as the kiln gets hotter" it is how FAST the kiln is getting hotter. What is important is the RATE of CLIMB. How many degrees per hour (or minute) the temperature is increasing.


From your paragraph the key points I got were: 1) cones are important and 2) they measure how your clay and glaze react to each other under certain temperature conditions. It is not all about "heat work." The longer you study the cones in accordance with the temperature you are firing, the clay you are using and the glazes applied--the better off you will be.


It IS all about heat work.... not about temperature (alone). Neil's cooking analogy is a good one.


best,

.................john
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Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

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#10 Lucille Oka

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Posted 03 November 2012 - 10:12 PM

I remember someone said "if you don't know the answer go and wedge some clay" when a simple question like the stages of clay development were presented. I think, if I was to guess, this is a similar question to the stages of clay development. So please don't send me to wedge clay. Somehow I missed this lesson in the guzzillion classes I took to get to this point.

Nelly



In defense of what I said here is the quote- "If the question seems elementary to you then you are no beginner go wedge up some clay".



John 3:16
"For God so loved the world that He gave His only begotten Son, that whosoever believeth in Him should not perish but have everlasting life".

#11 Lucille Oka

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Posted 03 November 2012 - 10:12 PM

Sorry this is the duplicate.

John 3:16
"For God so loved the world that He gave His only begotten Son, that whosoever believeth in Him should not perish but have everlasting life".

#12 Lucille Oka

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Posted 03 November 2012 - 10:12 PM

Sorry this post triplicated itself.

John 3:16
"For God so loved the world that He gave His only begotten Son, that whosoever believeth in Him should not perish but have everlasting life".

#13 Nelly

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Posted 03 November 2012 - 11:45 PM

In addition, as the kiln gets hotter, heat work should take less time (because it has already been done).


It is not "as the kiln gets hotter" it is how FAST the kiln is getting hotter. What is important is the RATE of CLIMB. How many degrees per hour (or minute) the temperature is increasing.


From your paragraph the key points I got were: 1) cones are important and 2) they measure how your clay and glaze react to each other under certain temperature conditions. It is not all about "heat work." The longer you study the cones in accordance with the temperature you are firing, the clay you are using and the glazes applied--the better off you will be.


It IS all about heat work.... not about temperature (alone). Neil's cooking analogy is a good one.


best,

.................john



Dear John,

Okay, once again, let me see if I can get this straight. Is IS about heat work but not only this aspect. It is a barometer of what your clay and glaze does together.

The different numbers tell you about the ramps or how quickly you move up the scale to arrive at the place that can be considered cone 7 despite the numbers being different.

In short, you can cook a roast fast or you can cook it slowly. Either way you will get there or the meat will be cooked.

If I want to speed up the cooking time, I will look to the far right of the chart. If I want to go slow, I will try to go the temperature as posted on the far left.

How is that??

I hope this sounds better.

Do know I opened the kiln. At cone 7 everything is better. The matt has that slight glisten that I like. The saturated iron is strong and does pick up detail. Thus, I think for the purposes of my glazes right now, I should stick to 7. What was interesting though was that my 6 cone was bent to what I would call 10 o'clock. The 7 was at 11 o'clock. I think that means I really didn't get to a complete cone 7 for some reason. The 8 was tall.

One more thing, I noticed the bottom pyrometer appears bare and there are small dark shavings underneath. Does this mean that I have blown off some special coating on these mechanisms or is it just the heat affecting the tip?? I just know, I am seeing a bunch of small black shavings under the bottom pyrometer or thermocouple?? I am not used to this internal pyrometer.

Has anyone else experienced this?? If not, I will likely call my pottery people on Monday to see if it is normal.

Thank you one and all for your help.

I think, this year, I should be the poster person for this forum? I hope you are smiling!! ;)

Thank you all again.

Nelly

#14 Nelly

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Posted 03 November 2012 - 11:54 PM


I remember someone said "if you don't know the answer go and wedge some clay" when a simple question like the stages of clay development were presented. I think, if I was to guess, this is a similar question to the stages of clay development. So please don't send me to wedge clay. Somehow I missed this lesson in the guzzillion classes I took to get to this point.

Nelly



In defense of what I said here is the quote- "If the question seems elementary to you then you are no beginner go wedge up some clay".

Not to worry, I will be wedging tomorrow as I contemplate a roast of beef and how this relates to the Orton cone chart ;)


Nelly





#15 Mark McCombs

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Posted 04 November 2012 - 01:59 AM

Do know I opened the kiln. At cone 7 everything is better. The matt has that slight glisten that I like. The saturated iron is strong and does pick up detail. Thus, I think for the purposes of my glazes right now, I should stick to 7. What was interesting though was that my 6 cone was bent to what I would call 10 o'clock. The 7 was at 11 o'clock. I think that means I really didn't get to a complete cone 7 for some reason. The 8 was tall.

Nelly



I'm glad to hear that it worked out for you. :)

It seems to me that from your description the you did not reach ^6 on the bottom shelf.
In reaching ^7, your 6 should be bent all the way over with its back broken and 7 should be just touching.
Did you have cones on other shelves? Might be quite a bit cooler on the bottom.
Mark
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#16 Nelly

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Posted 04 November 2012 - 02:59 AM


Do know I opened the kiln. At cone 7 everything is better. The matt has that slight glisten that I like. The saturated iron is strong and does pick up detail. Thus, I think for the purposes of my glazes right now, I should stick to 7. What was interesting though was that my 6 cone was bent to what I would call 10 o'clock. The 7 was at 11 o'clock. I think that means I really didn't get to a complete cone 7 for some reason. The 8 was tall.

Nelly



I'm glad to hear that it worked out for you. :)

It seems to me that from your description the you did not reach ^6 on the bottom shelf.
In reaching ^7, your 6 should be bent all the way over with its back broken and 7 should be just touching.
Did you have cones on other shelves? Might be quite a bit cooler on the bottom.


Dear All,

It is odd that the temperature was not reached on the bottom. I am not sure why except it may have something to do with those shavings I am finding under the thermocouple or pyrometer in this area of the kiln ?? I will take this into consideration when I fire tomorrow and will likely turn it up a touch more.

No, I did not have cones on the other shelves but I will do this tomorrow.

Nelly

#17 Lucille Oka

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Posted 04 November 2012 - 06:44 AM

Those bits of 'shavings' are bits of oxidation which flake off of the elements and the thermocouple. It is a bit of wearing away of the metals and eventually it will affect the temperature that the elements reach and the thermocouple's sensitivity to the heat readings.

Vacuum the ‘shavings’ out of the kiln. Keep it cleaned out after every firing. It isn't so bad when you bisque fire you can just brush them off of the ware. But you don't want those bits to fall onto the glazed ware while it is firing they will stick.

Because there is such a disparity between the cones, I tell folks to use the temperatures of the cones as a guide for the maturation of your clay and glazes and use the cone numbers as a reference for purchasing.

The Orton website has some valuable information that you may find helpful. The videos are really good too. There is one video that shows the melting of pyrometric cones it's really cool. Go to 'Resources' to view the videos.

http://www.ortonceramic.com/shop/



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"For God so loved the world that He gave His only begotten Son, that whosoever believeth in Him should not perish but have everlasting life".

#18 neilestrick

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Posted 05 November 2012 - 06:01 PM

If your kiln has zone control, which I'm assuming it does since you mentioned the bottom thermocouple, it should be firing more evenly. If that bottom thermocouple is looking really thin and worn out, replace it. It could be that it's worn out and not reading properly. Depending on what type of kiln you have, you may be able to adjust your thermocouples to be more accurate with the results shown by the cones. Look for Thermocouple Offset in your manual. Or just fire a cone hotter and don't mess with it.
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