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neilestrick

Cones And Soaking Times Theory

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Nearly every day on this forum someone, often me, refers to cones and their importance in the ceramic firing process. I understand how cones work. I explain it to my students all the time. But this week I found myself with a question about cones I've never encountered before.

 

When it comes to soaking (holding temperature) in order to achieve heat work, we always tell people to test it with actual cones. I've heard anywhere from 15 minutes to 1 hour of soaking is necessary in order to gain one cone. There's no consistency to the system.

 

Here's my recent experience that has me somewhat baffled: I used to fire to cone 8 in oxidation (electric). In order to increase the life of my elements a bit, I would fire to cone 6 with a 40 minute hold to reach cone 8. Now I fire to cone 6, and I finally tested the hold time to see how long it would take me to get from cone 4 to cone 6, and it came out to 75 minutes, almost twice as long as from cone 6 to cone 8!

 

The at a rate of climb of 108F/hr, which is what my firings use, the difference between cone 6 and cone 8 is only 48 degrees. The difference between cone 4 and cone 6 is 108 degrees. So can we assume that the greater the temperature gap, the longer the soak time in order to achieve the heat work? Those of you who soak for cones, what cones are you using, and how long is your soak time?

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If you can get the NCECA program for last year you can read a great presentation on the newest research on Heatwork. Basically the future of kiln programming will have to go to Heatwork rather than Cones ... it's their fault for giving us computers to play with!

 

Anyhow, my fabled firing of this week ... I ramped the computer to hit 2200F, held it for 20 minutes. Results - cone 7 on top, hard 8 in the middle and a regular 8 at the bottom. The controlled cooling did not go all the way, so I lost some of that Heatwork. Brand new elements on first high firing.

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Guest JBaymore

If you can get the NCECA program for last year you can read a great presentation on the newest research on Heatwork. Basically the future of kiln programming will have to go to Heatwork rather than Cones ... it's their fault for giving us computers to play with!

 

What she said!  Chris and I sat side by side for this presentation and it was FANTASTIC. 

 

I was refering to this same presentation in another posting on this subject elsewhere where I said that the programming of kiln controllers will be changing soon based upon this research.

 

best,

 

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

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I will have to see if I can find a video of that presentation. In trying to solve glaze problems, I have wondered if it is not just heat work but also temperature reached which may cause/solve glaze problems. I would think the glaze effects of reaching the heat work of cone 8 by firing to 6 with a long hold is not the same as firing to 8 with no hold.

 

I hope that makes sense. With electronic controllers we almost need some new words to make things clearer.

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Guest JBaymore

Here is the NCECA Journal in which the article would be:

 

https://netforum.avectra.com/eweb/shopping/shopping.aspx?site=nceca&webcode=shopping&shopsearch=journal&shopsearchcat=merchandise&productcat=publications&prd_key=5c8a2b47-4eb3-4989-80e0-8ae6d16a5052

 

best,

 

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

 

PS:  I have to go look at (find) my copy to see how extensive the piece is. 

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You are exactly right Diane ... Cones are a really outdated way of trying to measure what is happening inside your kiln if you are doing anything other than a straight forward Cone firing.

As I remember, the talk was presented by Orton, Skutt and the scientist involved, so I think we should see progress towards a new kind of language and numbering system that will stand for heatwork achieved, rather than cone temps. Then we won't have to fire by guess work and the parameters that change with the age of your elements, the size of your kiln load etc.

I too am trying to find my copy ....

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Who was the author/presenter of the Heat Work Presentation

 

Here is the NCECA Journal in which the article would be:

 

https://netforum.avectra.com/eweb/shopping/shopping.aspx?site=nceca&webcode=shopping&shopsearch=journal&shopsearchcat=merchandise&productcat=publications&prd_key=5c8a2b47-4eb3-4989-80e0-8ae6d16a5052

 

best,

 

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

 

PS:  I have to go look at (find) my copy to see how extensive the piece is. 

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Lets use rings, forget the cones

As an old organic chemist ... just make sure it is six member rings although I still like tetrahedrons

 

seriously though, I would be great to really get the true story on what “heat work†really means.

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I can see this all getting very complicated for beginners in the near future, what with so many Kiln Sitters still in use. Should be fun!

 

Why? Laws of physics or chemistry have not changed in our universe. New theories do not change how nor why event X happens. It only changes how we describe/understand that event. It still keeps happening as it did before, if conditions (like temperature) are right. Ceramics have been fired by smell and sight and gut feeling for a very-very long time before Josiah Wedgwood created accurately scaled pyrometric beads (1782).

 

Even if the chemical composition and behavior of cones tetrahedrons (marketing department did not like that word) is going to change and they get renumbered (has happened before) we adjust to the new measuring stick and march on.

 

Certain changes in claybody or glazes happen because certain temperatures are reached. One can run circles a round a greenware pot with a candle - it will never bisque or turn in to a stoneware.

 

For example, quartz inversion occurs at 573°C. Period. You can call that point a Cube Y, The 6 Ding-Dongs or 846.15 K, it still happens when required condition (temperature in this case) is met.

 

My point is, as long as you can repeat what you did and confirm somehow (colour, cone, laser beam, thermocouple/voltmeter etc) required temperatures are reached, you are fine.

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"My point is, as long as you can repeat what you did and confirm somehow (colour, cone, laser beam, thermocouple/voltmeter etc) required temperatures are reached, you are fine."

 

That is 100% true ... but no system of measurement is in place right now for people who manipulate their firings with the computer controls.

We take a shot in the dark at how long to hold at the end of the firing to hit a certain level of Heatwork ... then try to factor in the extra heat when we fire down. It was really good to hear they are working on it.

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I can see this all getting very complicated for beginners in the near future, what with so many Kiln Sitters still in use. Should be fun!

 

Why? Laws of physics or chemistry have not changed in our universe. New theories do not change how nor why event X happens. It only changes how we describe/understand that event. 

 

It could become confusing for beginners if we end up with two different systems- one for folks with Kiln Sitters and one for folks with digital controllers. One system seems to be confusing enough for some people. I'm not saying we shouldn't pursue it, I'm just saying it's going to be tough to educate everyone on two systems.

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Guest JBaymore

 

Because of the intrinsic properties of thermocouples, caution must be employed in relying on these devices to successfully control a firing process. A model for heatwork based on time-temperature information is discussed and the implications on potential under- and over-firing are examined.

 

 

THIS is the core of what I have been refering to. 

 

It is the current MODEL that is used in computerized controllers that will likely be changing... not the concept of the way cones behave nor the whole basis for the concept of heatwork.  Potential change is coming from a better understanding of what "heatwork" is all about.  Some things about ceramic process ar dependent not solely on the temperature achieved,... but also on application of heat over time... as it always has been. 

 

The focus of the "big stuff" in the talk was the better understanding of the relationships of heat energy applied over time during the upper portion of the firing process for any given end point cone range.

 

And as Chris and I discussed at the time in the lecture hall,... the presentation was likely "over the heads" of probably 90% of the people in the room.  As soon as the calculus slides went onto the screen............... you could "feel" people tuning out; many got up and left.  And that was the real meat in this presentation.

 

In the end what this will mean is simply more accurate modeling of firing behaviors for people who use controllers, and thefore more of the variables under a bit more control, and therefore more consistent results.

 

best,

 

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

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Well, I was totally lost at first John, but once they started showing picture graphs of what they were talking about it started to make total sense. Sadly people did leave before they had a chance to see the future these people are working on.

Unfortunately NCECA is sometimes like that ... a lecture that starts off boring either stays that way for an hour ... Or takes off.

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the presentation was likely "over the heads" of probably 90% of the people in the room. As soon as the calculus slides went onto the screen.

 

I'd like to see that John

 

I was thinking of writing a computer program that calculated total “heat work†for a particular ramp.

The simplest thing would be just to sum degree hours over the significant part of the run. The question being, what is significant in heat work. Is it the last few hundred degrees or should you start form quartz inversion?

 

This doesn't seem right either because there seems to be a significant difference between holds and ramps before reaching max temperature and holds and descending ramps after for each different glaze.

 

The main thing I would be looking for is whether this information would give you any more of an idea of how you might proceed than cones or peep hole fire color or

any of the other things mentioned.

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As I see it, there are other area's that are not viewed in the heat work discussion, body mass and glaze thickness as well as the lifespan of thermocouples and elements.

I think the issue is accepting the wide range of possibilities and learning by experience the how's and why's of firing. It can not be reduced to a firing schedule where others have taken the responsibility (by way of program firing) instead of the individual putting in the years of work to learn.

The fluxes in one clay body vs another with change the results of heat work on one clay body vs another. These issues will alway demand that the potter be more in control than the program. .

Just another 2 cents in the pot.

Wyndham

Min and Patsu like this

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I understand the concept of heat work. What I don't understand is what's the merit of soaking for an extended period of time to reach a certain cone as opposed to just raising the kiln to that temperature more quickly. Given that there are merits of this  approach, how far can you push it and why? I know that Stephen Hill's firing schedules make a lot of use of soaking.

 

I know that I can test all the stuff for 10 years but at 69, I need more of a shortcut

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... The fluxes in one clay body vs another with change the results of heat work on one clay body vs another. These issues will alway demand that the potter be more in control than the program. .

Just another 2 cents in the pot.

Wyndham

Exactly and those events are far from random or require magic. Everything that happens, in any material we work with, can be defined by temperature and time. The question is, how can one measure this temperature and do it reliably - repeat it over and over again.

For example, me yard stick is temperature and time, numbers on the controller screen. It's just a value, like those eyeballed degrees of bent cones, you can barely see in raging inferno from that tiny peephole of your kiln.

 

If you change the clay body and are sharp enough, to figure out how change the firing schedule on fist try, you deserve fine result. Rest of us/them, must fail few times and only then, hopefully, adjust the schedule accordingly to succeed.

 

I highly recommended this brutal experiment - pull all the modern gadgets from your kiln and fire it "blind", fully loaded with your best work. Use your eyes, nose and gut feeling, see what happens. Find out, are you really fit for the job or not.

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I highly recommended this brutal experiment - pull all the modern gadgets from your kiln and fire it "blind", fully loaded with your best work. Use your eyes, nose and gut feeling, see what happens. Find out, are you really fit for the job or not. 

 

I used to do that with the wood kiln, and sometimes with the gas kiln, but it's nearly impossible to see what's happening in my electric kiln. The peeps are tiny! I get your point, though. But I don't necessarily think going 'pure' is really a judge of firing skill. By that argument we should do away with all tools, and handbuild everything and fire it in pits. There's nothing wrong with modern gadgets if you understand what they are doing, and not just blindly trusting/using them. I don't turn off spell check even though I don't need it...

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I understand the concept of heat work. What I don't understand is what's the merit of soaking for an extended period of time to reach a certain cone as opposed to just raising the kiln to that temperature more quickly. Given that there are merits of this  approach, how far can you push it and why? I know that Stephen Hill's firing schedules make a lot of use of soaking.

 

I know that I can test all the stuff for 10 years but at 69, I need more of a shortcut

 

Firing to a lower temperature and soaking can add richness to a glaze, and can also extend element life. I noticed a 25% increase in element life when I started soaking cone 6 for 40 minutes to get to cone 8, instead of firing all the way to cone 8. Two things cause wear on elements: high temperature and cycling on and off. In my very unscientific test, firing hotter wore them out faster than cycling to hold temp.

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Docweathers - in the book Mastering Cone 6 Glazes, John & Roy illustrate how various glazes change when they are allowed to soak. For myself, I like to know the whole kiln has reached temp, not just the area near the thermocouple. Soaking gives me more even firings top to bottom.

 

Mart - I always say that every potter should help to fire a wood kiln at least once ... Just to hear how it speaks to you, to give your full attention to a process, to finally feel why they call it FIRING a kiln. Then go home and give your electric kiln a hug. : - )

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neil, you're right about the wearing out of elements. The closer they get to their max temp about 2385 or so, the shorter the life. I wonder about the dimishing return on longer firing at lower temp for better life span vs wearing out of relays over a prolong firing, something to consider.

Wyndham

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Guest JBaymore

Then go home and give your electric kiln a hug. : - )

 

:lol:  :lol:  :lol: With the complexities of firing noborigama, sometimes I very much feel that way, Chris.  :lol:  :lol:  :lol:

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well yes, firing glazes requires dealing with multiple variables beyond time and temperature, but for any given gaze there should be an optimum ramp that gives the best results at the least cost which might be found by heat work calculations rather than pure trial and error.

 

I bisque fires some pieces for a woman who said that her mentor uses a 16 hour cycle up to cone 014.  I asked here how thick the pieces were that he fired and she said they were ordinard pots and mugs. I told here I would not do it unless she let me fire them with my regular 5 hour bisque cycle. She was very uneasy with this but guess what? They turned out fine anyway. I can't imagine the wasted time and energy  this guy has been using.But by god, I suppose he can say he never lost a pot!

 

We are much better at predicting weather since we developed computers than when grandpa felt his joints acting up. I see no reasone why firing ceramics should remain a black art.

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