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MichaelP

What bisque firing schedule do you use?

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LovesPurple    0

I have a pretty simplistic approach to bisque firing. I put my bone dry "masterpieces" in my oven, turn the oven light on, and leave it overnight. In the morning I load the kiln and fire to 04. With my old kiln I just turned the knobs every hour. I started with 0 (low), then 10, 30, 50, 70, 100 - then just waited for the sitter to trip (I put an 03 bar in the sitter). I had no idea what I was doing when I started, and never had a problem.

 

Now, I am a little spoiled and have a firemate controller on one kiln and a digital on the other - love the fact that I can just tell it to go to 04 and let it do it's thing! With both, it takes about 4 hours to bisque fire to 04. I go much slower when I glaze fire. rolleyes.gif

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Mart    23

I have a Bentrup TC88 controller and this only speaks in Centigrades and hours :)

I changes mine to 0->600°C in 6h and 2 h 30 min -> 1013°C. This is something like cone 06

 

Is this too long for bisque?

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MichaelP    21

I have a pretty simplistic approach to bisque firing. I put my bone dry "masterpieces" in my oven, turn the oven light on, and leave it overnight. In the morning I load the kiln and fire to 04.

 

Now, I am a little spoiled and have a firemate controller on one kiln and a digital on the other - love the fact that I can just tell it to go to 04 and let it do it's thing! With both, it takes about 4 hours to bisque fire to 04. I go much slower when I glaze fire. rolleyes.gif

 

So you don't use any ramp and soak with your digitally controlled ovens? You dry the wares in your oven, and then just shoot from the ambient temperature straight to Cone 04 in the kiln at full speed, correct?

 

How long do you use this speedy approach for? What kind of item do you make?

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Mart    23

I have a pretty simplistic approach to bisque firing. I put my bone dry "masterpieces" in my oven, turn the oven light on, and leave it overnight. In the morning I load the kiln and fire to 04.

 

Now, I am a little spoiled and have a firemate controller on one kiln and a digital on the other - love the fact that I can just tell it to go to 04 and let it do it's thing! With both, it takes about 4 hours to bisque fire to 04. I go much slower when I glaze fire. rolleyes.gif

 

So you don't use any ramp and soak with your digitally controlled ovens? You dry the wares in your oven, and then just shoot from the ambient temperature straight to Cone 04 in the kiln at full speed, correct?

 

How long do you use this speedy approach for? What kind of item do you make?

 

 

Sorry but I am sure I must be missing something because I am not a native English speaker. :)

You dry the wares in your oven , and then just shoot from the ambient temperature straight to Cone 04 in the kiln at full speed, correct?

 

No, I let them dry before I place anything in to the kiln. Then I let the kiln heat up 100C per hour up to 600 C (1112F / cone 022) (total 6 hours) and from there I go a bit more that 160 C/h up to 1013C or 1855F (cone 06?) (about 2.5 h), soak 3 min at 1013C and let it cool naturally. Cooling takes about 14+ h so the whole process is 24 h. I usually crack the lid around 150C to speed up the cooling.

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neilestrick    1,379

I think people over think the bisque schedule. There is so much variability within the range of acceptable firing schedules that I think you're more than likely to have no problems with most schedules. For most pots of average size and thickness:

 

1. For manual kilns, an hour on low, an hour on medium, then high till done.

2. For digital kilns, Fast Bisque on L&L & other Bartlett controllers with that option, or Medium speed on Skutt & others with that option. These programs have been tested, and work for most clay bodies in most situations. That's why they're in the controller.

3. If your pots are not totally dry, dry them out on low or with a preheat.

4. If your pots are really thick or really large, fire slower.

 

You can, of course, fire pretty fast if your pots and your clay can handle it. I've been known to pull handles on mugs, put them immediately into the kiln, dry them for 4 hours, then do a 4 hour bisque firing. My porcelain has no problem with it, but I don't know if my stoneware would be clean enough from a firing that fast. And I certainly wouldn't trust most student pots.

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Mart    23

I think people over think the bisque schedule. There is so much variability within the range of acceptable firing schedules that I think you're more than likely to have no problems with most schedules. For most pots of average size and thickness:

 

1. For manual kilns, an hour on low, an hour on medium, then high till done.

2. For digital kilns, Fast Bisque on L&L & other Bartlett controllers with that option, or Medium speed on Skutt & others with that option. These programs have been tested, and work for most clay bodies in most situations. That's why they're in the controller.

3. If your pots are not totally dry, dry them out on low or with a preheat.

4. If your pots are really thick or really large, fire slower.

 

You can, of course, fire pretty fast if your pots and your clay can handle it. I've been known to pull handles on mugs, put them immediately into the kiln, dry them for 4 hours, then do a 4 hour bisque firing. My porcelain has no problem with it, but I don't know if my stoneware would be clean enough from a firing that fast. And I certainly wouldn't trust most student pots.

 

 

Low? High? Medium? Huhh... Can you please translate "Fast Bisque", "Medium speed" etc to something understandable like temperatures in C or F and time in hours to reach the temperature? :)

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LovesPurple    0

I have a pretty simplistic approach to bisque firing. I put my bone dry "masterpieces" in my oven, turn the oven light on, and leave it overnight. In the morning I load the kiln and fire to 04.

 

Now, I am a little spoiled and have a firemate controller on one kiln and a digital on the other - love the fact that I can just tell it to go to 04 and let it do it's thing! With both, it takes about 4 hours to bisque fire to 04. I go much slower when I glaze fire. rolleyes.gif

 

So you don't use any ramp and soak with your digitally controlled ovens? You dry the wares in your oven, and then just shoot from the ambient temperature straight to Cone 04 in the kiln at full speed, correct?

 

How long do you use this speedy approach for? What kind of item do you make?

 

 

Oh, heavens no! I put it in the oven the night before to make sure it is absolutely bone dry. When I had my old kiln I would turn it up a little every hour until it was going full blast. The Firemate controller I have on my "new" kiln ramps it up at a safe speed, which happens to be faster than what I was doing manually. And, my kilns are small.

 

I make a lot of tiles and small stuff.

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MichaelP    21

I wonder if stoneware will have enough time to get rid/ougas all organic impurities if ramping from the anbient to Cone 04 takes only 4 hours.

 

Do you use stoneware and glaze it routinely? Do you glaze at about cone 5-6 or use a low temp stuff? Did you notice glazing defects indicative of incomplete impurities burnout?

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Mart    23

I wonder if stoneware will have enough time to get rid/ougas all organic impurities if ramping from the anbient to Cone 04 takes only 4 hours.

 

Do you use stoneware and glaze it routinely? Do you glaze at about cone 5-6 or use a low temp stuff? Did you notice glazing defects indicative of incomplete impurities burnout?

 

 

 

I only use stoneware clay that can be fired up to 1300C and glazes cone 6-9 (1240-1280C).

What I understand is that 500C-800C (cone 022-015?) range is really important because this is when you finally get rid of all the organic matter including carbon, sulfur etc. Pro's write it's good to go through that temp range "slowly" but they never bother explaining what "slowly" means in this context. angry.gif100 C per h? 150 C/h? What is "slowly"?

 

 

BTW, I changes my bisque firing schedule and now I go up to 1013 C (06) .

 

This is my bisque firing schedule:

From ambient to 600C in 300 minutes, and from 600C to 1013C in 150 minutes and then letting it cool naturally.

 

What do you think about this schedule? Is there any point adding a 1-3 min soak at the top temperature?

I personally like the result. Pieces are strong enough and easy to glaze.

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Studio 491    0

I have a small, old, reconditioned electric kiln with two knobs. I bisque to cone 08 and glaze fire to cone 6.

I have spreadsheet I have used to track my firings (I found I cannot post it here). I would be happy to send this to you. It's not perfect, but it is a start.

 

-Jane

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MichaelP    21

I have a small, old, reconditioned electric kiln with two knobs. I bisque to cone 08 and glaze fire to cone 6.

I have spreadsheet I have used to track my firings (I found I cannot post it here). I would be happy to send this to you. It's not perfect, but it is a start.

 

-Jane

 

Thank you for the offer, Jane. Please check your PM.

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I wonder if stoneware will have enough time to get rid/ougas all organic impurities if ramping from the anbient to Cone 04 takes only 4 hours.

 

Do you use stoneware and glaze it routinely? Do you glaze at about cone 5-6 or use a low temp stuff? Did you notice glazing defects indicative of incomplete impurities burnout?

 

 

I only use stoneware clay that can be fired up to 1300C and glazes cone 6-9 (1240-1280C).

What I understand is that 500C-800C (cone 022-015?) range is really important because this is when you finally get rid of all the organic matter including carbon, sulfur etc. Pro's write it's good to go through that temp range "slowly" but they never bother explaining what "slowly" means in this context. angry.gif100 C per h? 150 C/h? What is "slowly"?

 

 

 

Insuffucient offgassing, and the resulting bloating issues that only make themselves known after the glaze firing, have been an issue at the studio where I work. Last summer we introduced a new clay body (Laguna #65) which presented lots of bloating... which in turn presented the need for lots of research and troubleshooting by me.

 

To note, we are primarily an educational studio, running very tightly packed kilns, often with many thick pots within the load. The advice from Laguna was to slow down the bisque. I didn't have to tweak much... mostly in that critical range leading up to 1600F. The suggested "slow" was 200F/Hour (93C/Hour).

 

While I eventually gave up on the #65 clay (swapping it for #66 which has presented none of the bloating issues) I have a bisque program I am quite happy with:

50F/Hour to 200F - Hold 4:00

200F/Hour to 1600F - No Hold

500F/Hour to 1800F - Hold 0:15

 

The exhaust is mounted to the lowest ring of the kiln. I leave the top peep open to create a stronger draft to help clear out the offgassed organics.

 

If you are firing your bisque with a looser pack, or full of pots you know to be totally bone dry, you could probably safely shave time from the front end of this program... a short hold, or not hold at all after the first ramp.

 

Hope this helps some.

 

Chris

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Pres    896

I wonder if stoneware will have enough time to get rid/ougas all organic impurities if ramping from the anbient to Cone 04 takes only 4 hours.

 

Do you use stoneware and glaze it routinely? Do you glaze at about cone 5-6 or use a low temp stuff? Did you notice glazing defects indicative of incomplete impurities burnout?

 

 

I only use stoneware clay that can be fired up to 1300C and glazes cone 6-9 (1240-1280C).

What I understand is that 500C-800C (cone 022-015?) range is really important because this is when you finally get rid of all the organic matter including carbon, sulfur etc. Pro's write it's good to go through that temp range "slowly" but they never bother explaining what "slowly" means in this context. angry.gif100 C per h? 150 C/h? What is "slowly"?

 

 

 

Insuffucient offgassing, and the resulting bloating issues that only make themselves known after the glaze firing, have been an issue at the studio where I work. Last summer we introduced a new clay body (Laguna #65) which presented lots of bloating... which in turn presented the need for lots of research and troubleshooting by me.

 

To note, we are primarily an educational studio, running very tightly packed kilns, often with many thick pots within the load. The advice from Laguna was to slow down the bisque. I didn't have to tweak much... mostly in that critical range leading up to 1600F. The suggested "slow" was 200F/Hour (93C/Hour).

 

While I eventually gave up on the #65 clay (swapping it for #66 which has presented none of the bloating issues) I have a bisque program I am quite happy with:

50F/Hour to 200F - Hold 4:00

200F/Hour to 1600F - No Hold

500F/Hour to 1800F - Hold 0:15

 

The exhaust is mounted to the lowest ring of the kiln. I leave the top peep open to create a stronger draft to help clear out the offgassed organics.

 

If you are firing your bisque with a looser pack, or full of pots you know to be totally bone dry, you could probably safely shave time from the front end of this program... a short hold, or not hold at all after the first ramp.

 

Hope this helps some.

 

Chris

 

 

Sounds primitive, but I water smoke until my hand no longer feels any moisture in the air coming from the kiln. then I check the same way on my climb to 1000 F. If any dampness is felt, I hold for a while. My bisques are very tightly packed usually getting 3-4 glaze loads per bisque.

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Pres    896

Pres,

 

Forgive my ignorance... water smoke?

 

 

Sorry, old foggie language. Firing the kiln with lid propped, or peeps out. Some call it candling, I have always known it as water smoking, all a matter of semantics.

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Pres,

 

Forgive my ignorance... water smoke?

 

Sorry, old foggie language. Firing the kiln with lid propped, or peeps out. Some call it candling, I have always known it as water smoking, all a matter of semantics.

 

Thanks, Pres!

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good question!

 

as many answers as potters firing. answering for someone truly new to this and assuming they have a manual kiln i offer the following.

 

my first kiln, a paragon electric about 18 inches inside diameter and about 18 inches deep, came with an instruction book when i bought it in 1972. it said to put the bottom switch on low for one hour followed by the middle switch on low one hour later and the top switch on low one hour later. lid propped an inch and all peephole plugs out.

 

 

then follow the same sequence with the medium switches and at the end of the six hours since the beginning, start putting the high switches on. at that point check for possible water vapor leaving through the peepholes and the top using a mirror to see if it clouds up. finding NO steam on the mirror, proceed. once the bottom high switch goes on, the peephole plugs go in and the top is closed. do not burn yourself at this point and carefully lower the top with a long, strong metal tool so you do not bang it closed. removing the prop is tricky too, be prepared to get it safely to a safe surface until it cools. kitchen tongs, long ones, work here. they will bend if you try to use them to lower the lid.

 

 

the firing after all the switches are on high should only be a few,( 3- 5) hours depending on your element's age and condition. i fire to cone 04 these days since losing 3 loads to underfired bisque in 1990. have never had anything go wrong using this schedule even now with a much bigger automatic kiln fired to cone 6 with raw glazed work and the occasional refire on a piece i didn't like all in the same firing. now that i said that watch what will happen to the next one!!

 

here in florida i have a smaller manual kiln with a timer as well as a kiln sitter. never having a timer i set it for 10 hours the first time i fired this used kiln and learned that 5 hours is enough. have no idea of the element's condition. though i prefer to spray glaze and fire raw, i have to bisque here and take everything north to glaze it at home in a larger space.

 

 

hope this helps someone new.OOOHHH! YES!!! if you are new, start right and keep a log of exactly what you do so if anything happens you can repeat or avoid it.

 

 

 

Dear Old Lady,

 

 

I use an electric Skutt kiln and would like to know if you plug even the top peep hole while firing? The good "ol instruction manual thinks leaving the top hole open during both bisque and glaze firing. I am fairly new with electric kiln firing. Please advise? Thank You.

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neilestrick    1,379

Leave the top peep open for the entire firing unless your kiln has a downdraft vent, in which case all peeps should be plugged.

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Mart    23

I wonder if stoneware will have enough time to get rid/ougas all organic impurities if ramping from the anbient to Cone 04 takes only 4 hours.

 

Do you use stoneware and glaze it routinely? Do you glaze at about cone 5-6 or use a low temp stuff? Did you notice glazing defects indicative of incomplete impurities burnout?

 

 

 

I only use stoneware clay that can be fired up to 1300C and glazes cone 6-9 (1240-1280C).

What I understand is that 500C-800C (cone 022-015?) range is really important because this is when you finally get rid of all the organic matter including carbon, sulfur etc. Pro's write it's good to go through that temp range "slowly" but they never bother explaining what "slowly" means in this context. angry.gif100 C per h? 150 C/h? What is "slowly"?

 

 

BTW, I changes my bisque firing schedule and now I go up to 1013 C (06) .

 

This is my bisque firing schedule:

From ambient to 600C in 300 minutes, and from 600C to 1013C in 150 minutes and then letting it cool naturally.

 

What do you think about this schedule? Is there any point adding a 1-3 min soak at the top temperature?

I personally like the result. Pieces are strong enough and easy to glaze.

 

 

Correction: This actually 700-900 and as I'w read, some of the sulfur can actually hang around up to 1149 C

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CarolR    0

post-41049-136927461003_thumb.jpg

 

I'm having some problems with bisque firings and would like to run this by you...

 

I use stoneware which I underglaze at leather hard, then I sgraffito the piece. I let it get to bone dry and do the bisque in an old kiln - it has 4 on/off switches; the manual said to flip one switch an hour and then wait till the kiln sitter turns it off (^04). then I apply clear glaze to the cooled work and fire to ^5 using a newer kiln with an electronic controller.

 

Then I started having a problem. After the glaze firing some of my pieces had areas, usually circular, where the it looks like the glaze has pulled away, taking the under glaze with it. So there's a small area, sometimes several all near each other, where the clay body is exposed. In the photo, hopefully you can see the white spots, center right. Because I use their products, I called Amaco for help. I was told my bisque firing was too fast, that out gassing was not complete. And I was told a bisque to ^04 should take 10-12 hours! So now, hearing about these fast bisques, I'm confused.

 

I was an advocate of bisqueing as fast as possible - my little old kiln could fire off in 5 hours. But lately that doesn't seem to be working for me, so I'm going to to do a really slow bisque next time, as Amaco recommends. But why is it that some of you have no problems with a fast bisque? Wouldn't incomplete out gassing affect your glazes? Any thoughts on this? Thanks!

post-41049-136927461003_thumb.jpg

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OffCenter    82

post-41049-136927461003_thumb.jpg

 

I'm having some problems with bisque firings and would like to run this by you...

 

I use stoneware which I underglaze at leather hard, then I sgraffito the piece. I let it get to bone dry and do the bisque in an old kiln - it has 4 on/off switches; the manual said to flip one switch an hour and then wait till the kiln sitter turns it off (^04). then I apply clear glaze to the cooled work and fire to ^5 using a newer kiln with an electronic controller.

 

Then I started having a problem. After the glaze firing some of my pieces had areas, usually circular, where the it looks like the glaze has pulled away, taking the under glaze with it. So there's a small area, sometimes several all near each other, where the clay body is exposed. In the photo, hopefully you can see the white spots, center right. Because I use their products, I called Amaco for help. I was told my bisque firing was too fast, that out gassing was not complete. And I was told a bisque to ^04 should take 10-12 hours! So now, hearing about these fast bisques, I'm confused.

 

I was an advocate of bisqueing as fast as possible - my little old kiln could fire off in 5 hours. But lately that doesn't seem to be working for me, so I'm going to to do a really slow bisque next time, as Amaco recommends. But why is it that some of you have no problems with a fast bisque? Wouldn't incomplete out gassing affect your glazes? Any thoughts on this? Thanks!

 

 

04 is a pretty high bisque so I think Amaco is wrong. The cone you should bisque to depends on the clay. I use a lot of different clays and for some I only bisque to cone 015 to save time and elect. Others to cone 08. Only one clay I use, Lizella Red, needs to be fired to cone 04. It has a lot of organic matter in it and other impurities so I bisque that high to get rid of that and avoid out-gassing. I fire all my bisques as fast as possible. Just slow, depending on how big and thick the pots are, to 250 degrees (to be sure I'm well-past boiling point) and then full-speed to finish. You do a lot of work on your mugs so it is probably something as simple as oil from your hands on bisqued ware or other contaminant or incompatible underglaze, etc.

 

Jim

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