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#1 Isculpt

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Posted 06 October 2012 - 09:36 AM

I have always fired sculptures with walls that varied from 1/4" to 1/2" or more, so I've used a long bisquing schedule suggested to me by a very cautious functional potter friend. Probably too cautious, at 8 hours with the lid open and then 2 hours with lid lowered, then 4 hours on low and 4 hours on medium then whatever it takes to reach desired cone. But today I'm firing some small jewelry pendants that vary from 1/8"-1/4" in thickness. Can someone suggest a suitable electric firing schedule? I'm taking them to 04 to bisque and then on the next firing to 06 after underglazing, and then 06 again after washing them in copper carbonate to get the nice metallic blacks in the crevices. I wish I didn't have to fire 3 times, but I've found that underglazing my green sculptures ends up softening some details, and it's not possible to put the copper carbonate on top of the unfired underglazes since it has to be wiped off so that the cc remains only in the crevices. So as usual, I'm under the gun and looking for a way to cut some time!!

#2 OffCenter

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Posted 06 October 2012 - 10:10 AM

I have always fired sculptures with walls that varied from 1/4" to 1/2" or more, so I've used a long bisquing schedule suggested to me by a very cautious functional potter friend. Probably too cautious, at 8 hours with the lid open and then 2 hours with lid lowered, then 4 hours on low and 4 hours on medium then whatever it takes to reach desired cone. But today I'm firing some small jewelry pendants that vary from 1/8"-1/4" in thickness. Can someone suggest a suitable electric firing schedule? I'm taking them to 04 to bisque and then on the next firing to 06 after underglazing, and then 06 again after washing them in copper carbonate to get the nice metallic blacks in the crevices. I wish I didn't have to fire 3 times, but I've found that underglazing my green sculptures ends up softening some details, and it's not possible to put the copper carbonate on top of the unfired underglazes since it has to be wiped off so that the cc remains only in the crevices. So as usual, I'm under the gun and looking for a way to cut some time!!


No matter what anyone suggest here, you will still have to test to find what works best for your work. I know it sucks to take the time and "waste" the electricity but in the long run if you cut your firing time in half or even just shorten it by 20% or so it will save you lots of time and electricity. I'm firing a medium-sized kiln 2/3 empty every day now for over a week testing to see how much time I can cut off the cooling cycle for some iron saturate glazes. I have a test kiln but it is so small that test results don't translate to my mid and large kilns.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#3 JBaymore

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Posted 06 October 2012 - 10:31 AM

No matter what anyone suggest here, you will still have to test to find what works best for your work.


What he said!

And start off the structuring of the testing by studying up on exactly what happens when in a firing (tons of books on that stuff), so that your testing procedures make sense and are not just random.



best,

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

http://www.JohnBaymore.com

#4 Ace

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Posted 06 October 2012 - 07:20 PM

I have always fired sculptures with walls that varied from 1/4" to 1/2" or more, so I've used a long bisquing schedule suggested to me by a very cautious functional potter friend. Probably too cautious, at 8 hours with the lid open and then 2 hours with lid lowered, then 4 hours on low and 4 hours on medium then whatever it takes to reach desired cone. But today I'm firing some small jewelry pendants that vary from 1/8"-1/4" in thickness. Can someone suggest a suitable electric firing schedule? I'm taking them to 04 to bisque and then on the next firing to 06 after underglazing, and then 06 again after washing them in copper carbonate to get the nice metallic blacks in the crevices. I wish I didn't have to fire 3 times, but I've found that underglazing my green sculptures ends up softening some details, and it's not possible to put the copper carbonate on top of the unfired underglazes since it has to be wiped off so that the cc remains only in the crevices. So as usual, I'm under the gun and looking for a way to cut some time!!


How large is your kiln ?? You are either making an awful lot of pendants or else you must have quite a small kiln - which I presume is electric??
Assuming your work is truly dry before you bisque - you still need a minimum 1 hour pre heat - if in doubt take 4 hour pre heat with lid cracked a couple of inches - then you should schedule to fire to cone 04 over 10 - 12 hours with a one hour soak at temperature.
For your next (after bisque) fire to 06 - again give it a one hour pre heat and take it to 06 over 6 - 7 hours with a minimum 1 hour soak at max temperature.... This schedule should be the same for your final glaze firing.....
Good luck

#5 SmartsyArtsy

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Posted 06 October 2012 - 09:27 PM

One hour preheat for small completely dry ware? That seems very excessive to me I heat up slowly and never preheat pieces that are dry. And up to 1/4"


As for soaking at 04' does this ensure out gassing to prevent happening during glaze fire?

#6 DAY

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Posted 07 October 2012 - 05:33 AM

Remember, different clays have differing amounts of organic matter that need to burn out.<div>As others have said, testing will reveal the answer to your question!</div><div>Caution suggests firing inside a sagger, should an explosion occur.</div><div>I have read of a technique where wet greenware is fast fired in a wet (steam?) atmosphere.</div><div>Mister Google is the gentleman I always check with before embarking upon any new activity.<img src="http://ceramicartsda...fault/cool.gif" alt="B)" class="bbc_emoticon"></div>

#7 Isculpt

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Posted 09 October 2012 - 01:43 AM


I have always fired sculptures with walls that varied from 1/4" to 1/2" or more, so I've used a long bisquing schedule suggested to me by a very cautious functional potter friend. Probably too cautious, at 8 hours with the lid open and then 2 hours with lid lowered, then 4 hours on low and 4 hours on medium then whatever it takes to reach desired cone. But today I'm firing some small jewelry pendants that vary from 1/8"-1/4" in thickness. Can someone suggest a suitable electric firing schedule? I'm taking them to 04 to bisque and then on the next firing to 06 after underglazing, and then 06 again after washing them in copper carbonate to get the nice metallic blacks in the crevices. I wish I didn't have to fire 3 times, but I've found that underglazing my green sculptures ends up softening some details, and it's not possible to put the copper carbonate on top of the unfired underglazes since it has to be wiped off so that the cc remains only in the crevices. So as usual, I'm under the gun and looking for a way to cut some time!!


How large is your kiln ?? You are either making an awful lot of pendants or else you must have quite a small kiln - which I presume is electric??
Assuming your work is truly dry before you bisque - you still need a minimum 1 hour pre heat - if in doubt take 4 hour pre heat with lid cracked a couple of inches - then you should schedule to fire to cone 04 over 10 - 12 hours with a one hour soak at temperature.
For your next (after bisque) fire to 06 - again give it a one hour pre heat and take it to 06 over 6 - 7 hours with a minimum 1 hour soak at max temperature.... This schedule should be the same for your final glaze firing.....
Good luck



After John and Jim told me to "go **** myself"... well, it took me bit of time to come out of my swoon.. But now that I think on it, I blieve that their four letter word was "TEST"! As a compromise, with time running short etc, etc, I scrounged up some how to textbooks and read that I should never candle at the begining of firing nor soak at the end of firing. So tell me, what is the purpose of soaking in a bisque fire? And how do you intercept a cone sitter kiln to keep it from turning off when the tdesired emp has been reached so that you CAN soak??


Jayne

#8 DAY

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Posted 09 October 2012 - 06:04 AM

You can re-set a kiln setter After it trips simply by lifting the 'tripper' and carefully positioning the cone rest on it- just as you do with a cone in the kiln. Then push the button, and the kiln will go back on. STAY THERE! A good plan is to practice this with a cold, empty kiln.

#9 OffCenter

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Posted 09 October 2012 - 08:51 AM



I have always fired sculptures with walls that varied from 1/4" to 1/2" or more, so I've used a long bisquing schedule suggested to me by a very cautious functional potter friend. Probably too cautious, at 8 hours with the lid open and then 2 hours with lid lowered, then 4 hours on low and 4 hours on medium then whatever it takes to reach desired cone. But today I'm firing some small jewelry pendants that vary from 1/8"-1/4" in thickness. Can someone suggest a suitable electric firing schedule? I'm taking them to 04 to bisque and then on the next firing to 06 after underglazing, and then 06 again after washing them in copper carbonate to get the nice metallic blacks in the crevices. I wish I didn't have to fire 3 times, but I've found that underglazing my green sculptures ends up softening some details, and it's not possible to put the copper carbonate on top of the unfired underglazes since it has to be wiped off so that the cc remains only in the crevices. So as usual, I'm under the gun and looking for a way to cut some time!!


How large is your kiln ?? You are either making an awful lot of pendants or else you must have quite a small kiln - which I presume is electric??
Assuming your work is truly dry before you bisque - you still need a minimum 1 hour pre heat - if in doubt take 4 hour pre heat with lid cracked a couple of inches - then you should schedule to fire to cone 04 over 10 - 12 hours with a one hour soak at temperature.
For your next (after bisque) fire to 06 - again give it a one hour pre heat and take it to 06 over 6 - 7 hours with a minimum 1 hour soak at max temperature.... This schedule should be the same for your final glaze firing.....
Good luck



After John and Jim told me to "go **** myself"... well, it took me bit of time to come out of my swoon.. But now that I think on it, I blieve that their four letter word was "TEST"! As a compromise, with time running short etc, etc, I scrounged up some how to textbooks and read that I should never candle at the begining of firing nor soak at the end of firing. So tell me, what is the purpose of soaking in a bisque fire? And how do you intercept a cone sitter kiln to keep it from turning off when the tdesired emp has been reached so that you CAN soak??


Jayne


Gee, Jane, testing isn't that bad! I knew you'd get responses like the one above that recommends a ridiculous schedule so better to find out for yourself how fast you can fire. If you don't have time to test then just do a ridiculously slow firing. Maybe I missed something but I don't understand why you'd candle or soak at all. For what you're firing, I'd bisque by taking an hour or so to get to 220 then turn the kiln on high and leave it. If there is some reason you need to soak a bisque (and I can't imagine what it would be), do what Day said. You will have to rig up something (like leaning a metal rod against it) to keep the tripper up. Obviously, if you leave and forget the kiln, you will probably destroy the kiln and burn down the building and the fire could then spread to an orphanage.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#10 JBaymore

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Posted 09 October 2012 - 09:20 AM

After John and Jim told me to "go **** myself"...


Jayne,

Neither Jim nor I came anywhere near saying something like that (above) to you. I'm sorry if you felt that way, but that was perfectly sound and useful advice given the nature of what you described. And it was not stated in a particulary negative way either. Sometimes really good advice is not what you want to hear. Being "under the gun" and doing something that you've never done before on the basis of some untested recommendations from books or forums or friends is akin to going to Vegas and "letting it ride on red 22".

The prudent thing to do research / listen to the advice.... and then TEST before commiting to something that matters. The phrase "under the gun" you used says it mattered. But some pople DO go to Vegas and play roulette.....so to each his or her own. All any of us here can do from afar is try to help. It is up to the individual to accept or reject the ideas presented.

I too often see students getting ready for their senior thesis shows suddenly decide to try something new on some pieces slated for the show with no time left to re-make the work if the firing does not work out well. Sometimes that Vegas roulette wheel favors them,...... most times not. Drives me nuts when I see them do this. But they usually learn from the mistake ;) .

The reason that the "It depends" answer to everything about ceramics is always correct, is that there are a HUGE number of variables that we are manipulating/controlling throughout the process. Many of those variables affect the results. Many of those variables are critical to the results. Miss one detail in giving the "advice"..... and the results will not be what one expects. So taking in advice and then testing is THE way to get the ends you want.

In a field like medicine, it would be very difficult for a skilled physician to diagnose and accurately treat a patient utilizing this medium as a means to gather information. Lacking test data....... it is far more likely that he/she would not hit the bullseye a lot of the time. Taking an air transport type aircraft (737) that had an incapacitated pilot, and talking down to a landing even an experienced private license pilot by a pilot on the ground is not an easy taske and would bne very likely not to end well. It is no differnt for ceramics.

Yes.... there was a four letter word involved........ TEST. :)


On to the new questions................

Typically the kiln sitter is not the way to control the shutting off of the kiln at the end of the firing... although it seems to have become that to many people. It is really best as a "fail safe" device to shut off the kiln if neither the computerized controller (if there is one) nor the potter has shut off the kiln when it was suppoese to be shut off (via watching witness cones). The cone that is placed in the sitter prongs is then selected as a slightly HIGHER cone than the one to which the firing is intended to go. It prevents the kiln from "running away" too badly on the firing. It is another piece of the redundency that the kiln sitter with a firing duration timer provides.

So you should be able to soak at the end of the firing easily, because the kiln is not being shut off by the sitter.

And remember that cones do not measure temperature..... they measure heat work. What we care about is the effects on the ceramic chemistry provided by the application of heat energy. We can (within reason) get the same effects on the chemsirty by firing over a longer time to a lower temperature that we do firing over a shorter time to a higher temperature. That is indicated on the cone charts when you notice that the cone end point termpetures listed there are in columns organized by "rate of climb".

So a "soak" at a particular temperature will result in cones further melting. (It affects the ceramic chemistry the same way.... which is what cones are for.) So if you wait until cone 08 is tip to base ("down"), and then soak at whatever temperature is indicated on the pyrometer, you can expect that cone 07 will also be heading down soon. A soak should be happening before the end point cone is reached......... and should be bringing the firing TO the desired end point cone.


As to WHY someone might (effectively) decide TO soak.............

Remember, if you do a soak and you don't NEED to do that... you are simply wasting time and energy (hence, money).

Soaking can allow the temperature in the kiln to even out. Thermal lag in the various areas of density of the kiln's load will sometimes (often) result in varied heat penetration into the load. This allows the firing to become more even.

Soaking can give more time for certain chemical reactions to take place if they were not given appropriate time before that.


As to what is often known as "candling"..................

This is often a practice that is using the kiln not to "fire" the work, but as a drying unit. (Industry often uses unit that are called "driers".) The purpose is simply to make sure that the last of the water of formation has been driven off before you go above 212 F and any water present turns to steam. A tiny bit of water turns instantly to a large volume of steam... and we all know what that does if it happens within the walls of a clay object.

Another reason for possibly "candling" comes from fuel fired kilns of an older generation. The draft on a fuel fired kiln is determined to a very large extent on the temperature of the effluent exiting the exit flues at the top (for updraft) or the top of the chimney (for crossdraft of downdraft). Draft circulation on fuel kilns also has the impact of circulating the hot gase evenly throughout the kiln, thereby assuring even firing. So candling was used to help get the gases exiting the kiln hot enough to establish a draft patern that was appropriate to getting that particular kiln to fire well (as in "evenly"). On wood fueled kilns it was important to get the draft to flow well to get any primary air supply so that larger amounts of wod could be burned to advance the temperature.

So this aspect has no real application to an electric fired kiln. And it has little application to a forced air gas or oil kiln where the draft is established by mechanical means (the blower(s).


If I say "don't candle".......and your ware is wet.... you are not going to be happy. If I say don't soak, and your ware is a high carbon content clay and your electric kiln has poor ventilation system... you are not going to be happy. If I say "always candle" and your kiln does not need that..... you are wasting time and money. And so on.



When I do consulting work for kiln or ceramic technical clients, I ask more questions of them than they ask of me. It is exactly like being a doctor and trying to accurately diagnose something realatively complex. The doctor is going to recommend some testing before reaching the final diagnosis and treatment.

Hope that stuff helps.

best,

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

http://www.JohnBaymore.com

#11 Isculpt

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Posted 09 October 2012 - 11:05 AM

Jim & John, thank you both for your constant help and advice. And John, I was teasing :lol: about the four-letter word, poking fun at myself for looking for the easy way out. Thank you for the long and thorough answer!!!!!

#12 metal and mud

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Posted 09 October 2012 - 12:15 PM

After John and Jim told me to "go **** myself"...


Jayne,

Neither Jim nor I came anywhere near saying something like that (above) to you. I'm sorry if you felt that way, but that was perfectly sound and useful advice given the nature of what you described. And it was not stated in a particulary negative way either. Sometimes really good advice is not what you want to hear. Being "under the gun" and doing something that you've never done before on the basis of some untested recommendations from books or forums or friends is akin to going to Vegas and "letting it ride on red 22".

The prudent thing to do research / listen to the advice.... and then TEST before commiting to something that matters. The phrase "under the gun" you used says it mattered. But some pople DO go to Vegas and play roulette.....so to each his or her own. All any of us here can do from afar is try to help. It is up to the individual to accept or reject the ideas presented.

I too often see students getting ready for their senior thesis shows suddenly decide to try something new on some pieces slated for the show with no time left to re-make the work if the firing does not work out well. Sometimes that Vegas roulette wheel favors them,...... most times not. Drives me nuts when I see them do this. But they usually learn from the mistake ;) .

The reason that the "It depends" answer to everything about ceramics is always correct, is that there are a HUGE number of variables that we are manipulating/controlling throughout the process. Many of those variables affect the results. Many of those variables are critical to the results. Miss one detail in giving the "advice"..... and the results will not be what one expects. So taking in advice and then testing is THE way to get the ends you want.

In a field like medicine, it would be very difficult for a skilled physician to diagnose and accurately treat a patient utilizing this medium as a means to gather information. Lacking test data....... it is far more likely that he/she would not hit the bullseye a lot of the time. Taking an air transport type aircraft (737) that had an incapacitated pilot, and talking down to a landing even an experienced private license pilot by a pilot on the ground is not an easy taske and would bne very likely not to end well. It is no differnt for ceramics.

Yes.... there was a four letter word involved........ TEST. :)


On to the new questions................

Typically the kiln sitter is not the way to control the shutting off of the kiln at the end of the firing... although it seems to have become that to many people. It is really best as a "fail safe" device to shut off the kiln if neither the computerized controller (if there is one) nor the potter has shut off the kiln when it was suppoese to be shut off (via watching witness cones). The cone that is placed in the sitter prongs is then selected as a slightly HIGHER cone than the one to which the firing is intended to go. It prevents the kiln from "running away" too badly on the firing. It is another piece of the redundency that the kiln sitter with a firing duration timer provides.

So you should be able to soak at the end of the firing easily, because the kiln is not being shut off by the sitter.

And remember that cones do not measure temperature..... they measure heat work. What we care about is the effects on the ceramic chemistry provided by the application of heat energy. We can (within reason) get the same effects on the chemsirty by firing over a longer time to a lower temperature that we do firing over a shorter time to a higher temperature. That is indicated on the cone charts when you notice that the cone end point termpetures listed there are in columns organized by "rate of climb".

So a "soak" at a particular temperature will result in cones further melting. (It affects the ceramic chemistry the same way.... which is what cones are for.) So if you wait until cone 08 is tip to base ("down"), and then soak at whatever temperature is indicated on the pyrometer, you can expect that cone 07 will also be heading down soon. A soak should be happening before the end point cone is reached......... and should be bringing the firing TO the desired end point cone.


As to WHY someone might (effectively) decide TO soak.............

Remember, if you do a soak and you don't NEED to do that... you are simply wasting time and energy (hence, money).

Soaking can allow the temperature in the kiln to even out. Thermal lag in the various areas of density of the kiln's load will sometimes (often) result in varied heat penetration into the load. This allows the firing to become more even.

Soaking can give more time for certain chemical reactions to take place if they were not given appropriate time before that.


As to what is often known as "candling"..................

This is often a practice that is using the kiln not to "fire" the work, but as a drying unit. (Industry often uses unit that are called "driers".) The purpose is simply to make sure that the last of the water of formation has been driven off before you go above 212 F and any water present turns to steam. A tiny bit of water turns instantly to a large volume of steam... and we all know what that does if it happens within the walls of a clay object.

Another reason for possibly "candling" comes from fuel fired kilns of an older generation. The draft on a fuel fired kiln is determined to a very large extent on the temperature of the effluent exiting the exit flues at the top (for updraft) or the top of the chimney (for crossdraft of downdraft). Draft circulation on fuel kilns also has the impact of circulating the hot gase evenly throughout the kiln, thereby assuring even firing. So candling was used to help get the gases exiting the kiln hot enough to establish a draft patern that was appropriate to getting that particular kiln to fire well (as in "evenly"). On wood fueled kilns it was important to get the draft to flow well to get any primary air supply so that larger amounts of wod could be burned to advance the temperature.

So this aspect has no real application to an electric fired kiln. And it has little application to a forced air gas or oil kiln where the draft is established by mechanical means (the blower(s).


If I say "don't candle".......and your ware is wet.... you are not going to be happy. If I say don't soak, and your ware is a high carbon content clay and your electric kiln has poor ventilation system... you are not going to be happy. If I say "always candle" and your kiln does not need that..... you are wasting time and money. And so on.



When I do consulting work for kiln or ceramic technical clients, I ask more questions of them than they ask of me. It is exactly like being a doctor and trying to accurately diagnose something realatively complex. The doctor is going to recommend some testing before reaching the final diagnosis and treatment.

Hope that stuff helps.

best,

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


This discussion is very relevant for me, in fact I was planning on posting a query today about soaking.


I have an "Old Lady" Paragon electric kiln, one I call Old Lady because an old lady had it sitting in her garage for years and years and it's really old. I bought it nearly two years ago and, knowing nothing about what I was doing, commenced to learn to make pottery and use the kiln. For about a year she worked just fine, then the element connectors needed to be replaced, which I did, and the bricks needed to be patched, which I did. I got a pyrometer to monitor temperature inside the kiln--a real steep learning curve! I was happy with my works. Then my ^6 glazes stopped looking pretty and I noticed the temperature inside the kiln dropped 400 degrees in the first hour after the kiln sitter tripped. Those in the forum recommended performing a soak by re-setting the kiln sitter; I found how to do this exactly in a book on electric kiln firing whose name escapes me now. It didn't give exact details, so for my last glaze load I stayed by the kiln, waited until the sitter tripped and immediately turned the kiln back on, set the temperature to medium and set the timer for 4 hours. The glazes in this load, with this test, were gorgeous. The temperature dropped 200 degrees in 4 hours, so it was essentially successful. (I think.)

My question is: Does this soak--if it is that--make sense? Is it better to leave the temp at high and shut it off at a certain period of time or could this result in overfiring? It seems like the latter is true. I know someone will say--if it worked, it worked, and continue doing it that way, but I would like some opinions from you experienced potters out there. Is 4 hours too long? I have a nice big load nearly ready to fire this Saturday.




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