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What bisque firing schedule do you use?


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#21 Mart

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Posted 04 April 2013 - 03:04 PM

I have a small 60 liter electric kiln and this is what I use: 100 C/h up to 600 (6 hours) and from there I go about 150 C/h up to 956 and then let it cool down naturally.
I use stoneware clay.

#22 MichaelP

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Posted 05 April 2013 - 12:02 AM

Rakuu,

Do you find your schedule safe in terms of drying? Ever had pieces explode? Do you have to take any extraordinary efforts to pre-dry the ware? Are your items small and thin?

Any reason you prefer such a low cone as 08 for bisque firing?

Thank you for sharing your experience.

Mike

#23 Mart

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Posted 08 April 2013 - 12:39 PM

Rakuu,

Do you find your schedule safe in terms of drying?

I must be because I never had any problems.

Ever had pieces explode?


No (...knocking madly on wood)

Do you have to take any extraordinary efforts to pre-dry the ware?

Not at all. Larger and thicker stuff sits around for longer (4-5 days), everything else is usually ready to go the next day or two.

Are your items small and thin?

Usually not. I think they are more like "average".

Any reason you prefer such a low cone as 08 for bisque firing?


The guy I buy my clay and glazes from uses this this schedule for bisque firing and looks like it works fine. I was thinking about moving to 1013 C range (cone 06?). I'll try and see what happens with the next patch Posted Image

#24 MichaelP

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Posted 08 April 2013 - 03:06 PM

Interesting! Thank you.

#25 Mart

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Posted 10 April 2013 - 07:37 AM

Interesting! Thank you.


If you have ideas how to fine tune it, please let me know. I do not mind getting it done faster :)

#26 LovesPurple

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Posted 10 April 2013 - 10:23 AM

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. Posted Image

#27 Mart

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Posted 10 April 2013 - 11:00 AM

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?

#28 MichaelP

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Posted 10 April 2013 - 11:05 AM

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. Posted Image

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?

#29 Mart

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Posted 10 April 2013 - 01:57 PM


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. Posted Image

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.

#30 neilestrick

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Posted 10 April 2013 - 02:47 PM

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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#31 Mart

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Posted 10 April 2013 - 05:01 PM

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? :)

#32 LovesPurple

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Posted 15 April 2013 - 02:58 PM


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. Posted Image

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.

#33 MichaelP

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Posted 15 April 2013 - 06:19 PM

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?

#34 Mart

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Posted 27 April 2013 - 03:33 AM

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. Posted Image 100 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.

#35 Studio 491

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Posted 27 April 2013 - 10:19 AM

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

#36 MichaelP

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Posted 27 April 2013 - 03:01 PM

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.

#37 Chris Throws Pots

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Posted 29 April 2013 - 11:53 AM


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. Posted Image 100 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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#38 Pres

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Posted 29 April 2013 - 12:11 PM



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. Posted Image 100 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.

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/


#39 Chris Throws Pots

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Posted 29 April 2013 - 03:37 PM

Pres,

Forgive my ignorance... water smoke?

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#40 MichaelP

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Posted 29 April 2013 - 07:22 PM

Thank you Chris. This is very clear and helpful.




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