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TonyC

NEW RESULTS: L&L CNOS Adjustment Needed?

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Well...it looks like I need to refire and check the thermocouples under slower final segment heating conditions.   

For the record, all of my pots came out okay.   None of the glazes ran which actually surprised me after I saw the cones and saw the final temp.    Let's see what the next step tells us.   Thank you again for all of the feedback.

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5 minutes ago, TonyC said:

Well...it looks like I need to refire and check the thermocouples under slower final segment heating conditions.   

For the record, all of my pots came out okay.   None of the glazes ran which actually surprised me after I saw the cones and saw the final temp.    Let's see what the next step tells us.   Thank you again for all of the feedback.

That's the important thing, pots look good, it's a win!

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4 hours ago, TonyC said:

I fired the kiln this weekend for cone 6 glazes and have some results which prompt more questions for me.    I used self supporting cones this time.

       Setup:  Fast Glaze, Cone 6, 2232 F, No CNOS or TNOS adjustments, no Hold

       Final Reading:  2263 F, Total Time 4 hr 58 min,  Actual cones bent 5,6 AND 7 (See Pic)

I am confused that my final reading is so high.   Shouldn't the system have stopped at 2232 F?    My Hold time was set at 0.     As you can see, the Cone 7 is completely bent over (left to right - 5,6,7; front row - top shelf; back row - first shelf).    

Can anyone help explain? 

Have a look at the Orton Cone Chart, cone 6 self supporting cones info is in the first peach coloured column on the left. Run down to cone 6 on the left of the column then go along to the 3 figures for the final temp to reach cone 6. At the top of the column there are 3 heating rates, 27F, 108F and 270F. The final temp needed if you go at 27F / hour for the last 200 degrees is 2165, @ 108F it's 2232F and @270 it's 2269. If you just speed through the firing the glazes can look okay but the clay itself might not be fully mature if you have thick bottoms or walls. 108F/hour is a good safe rate to go at. 

One other thing, I'm seeing some bloats on your cones. When cones are fired really fast the outer skin of the cone can seal over and then the binders used in the making of the cones can't escape and you get bloats. For this reason I wouldn't trust your last set of cones as being accurate.(read the bit on the attachment to the right of the chart, it has a good explanation of cone behaviour)

 

 

 

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2 minutes ago, Min said:

Have a look at the Orton Cone Chart, cone 6 self supporting cones info is in the first peach coloured column on the left. Run down to cone 6 on the left of the column then go along to the 3 figures for the final temp to reach cone 6. At the top of the column there are 3 heating rates, 27F, 108F and 270F. The final temp needed if you go at 27F / hour for the last 200 degrees is 2165, @ 108F it's 2232F and @270 it's 2269. If you just speed through the firing the glazes can look okay but the clay itself might not be fully mature if you have thick bottoms or walls. 108F/hour is a good safe rate to go at. 

One other thing, I'm seeing some bloats on your cones. When cones are fired really fast the outer skin of the cone can seal over and then the binders used in the making of the cones can't escape and you get bloats. For this reason I wouldn't trust your last set of cones as being accurate.(read the bit on the attachment to the right of the chart, it has a good explanation of cone behaviour)

This is excellent information.   Thank you for noticing the cone bloating.   I plan to fire again using the Slow Glaze setting on my kiln where it finishes at 108F/hr.    I will keep everyone here posted on my new findings in a few days.   

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4 hours ago, neilestrick said:

  Also make sure your thermocouples are touching the ends of the tubes, otherwise they're further insulated from the heat.

Just checked the system and made sure that the thermocouple is touching the end of the ceramic tube.    I did notice that the tube could move (pulled forward) based on some spacers that are used in the system.   I am not sure if they need to be there in order to offset assembly away form outer kiln wall (for temp control??).   If not, I would remove 2 of the spacers.   I will take a pic and welcome your opinion as I didn't put the initial kiln together.  Pic 1 shows tube pulled forward against kiln outer wall...Pic 2 shows tube pushed back so that TC touches tube wall.   Not sure why the spacers are there other than to keep the unit further from the kiln wall.

TC Pulled Forward.jpg

TC Pushed Back.jpg

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6 minutes ago, neilestrick said:

@TonyC Do not remove the spacers. Just loosen the two screws that hold the TC in the block (the two screws in the middle), push the TC forward to the end of the tube, and tighten the screws.

Done.   So it is okay to have the TC lead exposed between the 2 ceramics?   I previously was more concerned about having ceramic tube (right) butt up against the ceramic  piece (left unit).   Check out pic.

TC.jpg

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Looks like the default cone 6 value in the cone table is 2199. If you are checking thermocouples when you remove them snap a picture of the first inch or two and post. I will look through the manual tonight and see if anything stands out.

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2 minutes ago, Bill Kielb said:

Looks like the default cone 6 value in the cone table is 2199. If you are checking thermocouples when you remove them snap a picture of the first inch or two and post. I will look through the manual tonight and see if anything stands out.

I didn't remove the thermocouples, but just ensured that they are pushed to the end of the tube.   See my last posting as I did adjust the way the thermocouples are set in place (thanks to Neil Estrick).     

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Neil, Bill, and others are addressing the settings vs witness cones and seem to focused on tweaking the controller settings.  That is OK, I guess, but before getting too deep in the that rabbit hole,

you should not be distracted from the two most important questions following any kiln firing: 

1. Has the clay body been fired to a state that the water absorption meets your requirements?  An absorption value near zero is the target recommended by Ron Roy the co-author of "Mastering Cone 6 Glazes", the handbook for cone 6 firing range.

2. Are the glazes mature?  Again see the handbook to evaluate the glazes.

If the answer to question 1 is yes, then the firing settings you used in this firing will get your clay body properly fired the next time you fire  If the answer is no, then the settings need to be adjusted to reach that target.    The same goes for question 2, 

but get question to yes, before working on question 2. 

LT

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9 minutes ago, Magnolia Mud Research said:

Neil, Bill, and others are addressing the settings vs witness cones and seem to focused on tweaking the controller settings.  That is OK, I guess, but before getting too deep in the that rabbit hole,

you should not be distracted from the two most important questions following any kiln firing: 

1. Has the clay body been fired to a state that the water absorption meets your requirements?  An absorption value near zero is the target recommended by Ron Roy the co-author of "Mastering Cone 6 Glazes", the handbook for cone 6 firing range.

2. Are the glazes mature?  Again see the handbook to evaluate the glazes.

If the answer to question 1 is yes, then the firing settings you used in this firing will get your clay body properly fired the next time you fire  If the answer is no, then the settings need to be adjusted to reach that target.    The same goes for question 2, 

but get question to yes, before working on question 2. 

LT

I would rather have the kiln firing accurately, then adjust the firing schedule as needed to reach the two goals you have mentioned above.

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14 minutes ago, Magnolia Mud Research said:

you should not be distracted from the two most important questions following any kiln firing: 

1. Has the clay body been fired to a state that the water absorption meets your requirements?  An absorption value near zero is the target recommended by Ron Roy the co-author of "Mastering Cone 6 Glazes", the handbook for cone 6 firing range.

2. Are the glazes mature?  Again see the handbook to evaluate the glazes.

LT

Thanks for a different perspective.    How am I testing for No. 1?    There were some cups, a bowl and a vase.   Not sure what my absorption requirement is other than the obvious.   Please share further what you mean.  Thank you.

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tony, hope you can work this out.   just a question.  why are you firing so fast, were you told to or do you have a specific reason to do so?   i have the same kiln you do and have always fired it at slow glaze because i single fire.  i am not advocating you fire at slow glaze, just wondering why you chose to fire so fast.

and, do not forget to let the person who gave you the wrong advice about cones know how it should be done.  you might save someone else a lot of trouble.

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Tony, 

The details for absorption test is in the Mastering Cone 6 Glazes. 

The test outline may be on Ron Roy’s website.  Search for Ron Roy pottery.

a quick test is to see how long it takes a mug kept full of water to leak onto a piece of paper.  Less than a month is NOT passing the test.☺️

 I will not be where I can look for the procedure until midweek earliest.  Let me know if I should start looking  after Thursday.

Neil, I will agree that we don’t agree on when one should start meeting specs.  That’s for another discussion thread.

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13 minutes ago, Magnolia Mud Research said:

Tony, 

The details for absorption test is in the Mastering Cone 6 Glazes. 

The test outline may be on Ron Roy’s website.  Search for Ron Roy pottery.

a quick test is to see how long it takes a mug kept full of water to leak onto a piece of paper.  Less than a month is NOT passing the test.☺️

 I will not be where I can look for the procedure until midweek earliest.  Let me know if I should start looking  after Thursday.

Neil, I will agree that we don’t agree on when one should start meeting specs.  That’s for another discussion thread.

https://ceramicartsnetwork.org/daily/ceramic-supplies/pottery-clay/testing-123-how-to-test-clay-bodies-to-find-the-right-sculpture-or-pottery-clay-for-your-work/

The weight method is one I've seen used.

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1 hour ago, oldlady said:

tony, hope you can work this out.   just a question.  why are you firing so fast, were you told to or do you have a specific reason to do so?   i have the same kiln you do and have always fired it at slow glaze because i single fire.  i am not advocating you fire at slow glaze, just wondering why you chose to fire so fast.

and, do not forget to let the person who gave you the wrong advice about cones know how it should be done.  you might save someone else a lot of trouble.

I had no special reason.   I read some comments along the way which made it sound like it didn't really matter.     I also think that my last Slow Bisque took so long that I was hoping something faster would make up for it.      I'm being kind...I think I was simply impatient :) .     

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1 hour ago, liambesaw said:

I just read this and can clearly perform the test.   I don't know what the results represent though.   Is there an 'absorption level' that should be achieved as a minimum?   What will the results 'tell' me?   

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3 minutes ago, TonyC said:

I just read this and can clearly perform the test.   I don't know what the results represent though.   Is there an 'absorption level' that should be achieved as a minimum?   What will the results 'tell' me?   

Will tell you how vitrified your clay is.  Some clays just don't vitrify well, so your mile may vary.  Basically if you fire to the rated cone of your clay, it won't leak water if the absorption rate is 2% or less.  If it's above 2%, the clay may weep.  I think magnolia was trying to say as long as your clay body is fired to maturity, that is the main concern.  Most clay manufacturers post the absorbancy,  it's good if you can compare your results to theirs.

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7 minutes ago, TonyC said:

I just read this and can clearly perform the test.   I don't know what the results represent though.   Is there an 'absorption level' that should be achieved as a minimum?   What will the results 'tell' me?   

I appear to have found an answer to my own question.   Important if the articles will be used in the microwave.   I just read that an absorption >2-3% can potentially cause problems in the microwave.   I will have to test for this as I suspect the mugs are going to get nuked.

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3 minutes ago, liambesaw said:

Will tell you how vitrified your clay is.  Some clays just don't vitrify well, so your mile may vary.  Basically if you fire to the rated cone of your clay, it won't leak water if the absorption rate is 2% or less.  If it's above 2%, the clay may weep.  I think magnolia was trying to say as long as your clay body is fired to maturity, that is the main concern.  Most clay manufacturers post the absorbancy,  it's good if you can compare your results to theirs.

Thanks.  I just read something similar which described the criticality of vitrification, especially for articles being microwaved.   Thanks for your feedback.   What a great site this is :)

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1 minute ago, TonyC said:

I appear to have found an answer to my own question.   Important if the articles will be used in the microwave.   I just read that an absorption >2-3% can potentially cause problems in the microwave.   I will have to test for this as I suspect the mugs are going to get nuked.

Iron rich bodies and iron rich glazes like temmoku are also something that behave poorly in a microwave.  Mainly they just get hot.

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