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What bisque firing schedule do you use?


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#41 Pres

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Posted 29 April 2013 - 09:01 PM

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.

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


#42 Chris Throws Pots

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Posted 01 May 2013 - 07:11 AM


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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handcrafted in Burlington, Vermont

 

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#43 Ravenware Studio

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Posted 01 May 2013 - 02:07 PM

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.
Ravenware Studio

#44 neilestrick

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Posted 01 May 2013 - 02:09 PM

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

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Posted 18 May 2013 - 12:06 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"?


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

#46 CarolR

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Posted 22 May 2013 - 09:10 PM

Attached File  image.jpg   77.32KB   8 downloads

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!

#47 OffCenter

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Posted 23 May 2013 - 08:07 AM

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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
E pur si muove.

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




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