Keba M Hitzeman on sun 30 dec 07
Bob,
With my little Olympic electric kiln, I bisque:
Low, propped open - 45 minutes
Low, lid closed - 1 hour
Medium - 1 hr. 30 min
High - until it trips.
This is what my friends at the local pottery shop suggested, and it has
worked very well for me. I have an under-kiln Ventmaster to the outside, so
I leave all the peeps in during the firing.
Keba
====================================
Keba Hitzeman
Dayton OH
Spanish - http://keba.hitzeman.com
Clay - http://yellowroomarts.blogspot.com
Coffee - coffee@enigma22.com
"The only thing necessary for the triumph of evil is for good men to do
nothing"
- Edmund Burke
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Bob Johnson
Sent: Sunday, December 30, 2007 19:07
To: CLAYART@LSV.CERAMICS.ORG
Subject: questions on efficient bisque firing
Does anyone have suggestions on an efficient bisque firing schedule for a
smallish electric kiln (an old Cress B-29-H, with a capacity of about 17" x
22")? I have lost the manual, so I don't know any more the exact firing
schedule the manufacturer recommended. And I have always suspected that I
was firing too conservatively and using too much energy. What I usually do
is this:
* Turn it on low with the lid open about 1-1/2" for a couple of hours.
* Turn up to medium for 2 more hours, with the lid open to the first
notch (about 1/2")
* Turn to high, close the lid, insert the peep-hole plugs, and continue
firing until the sitter turns it off---usually about 3 more hours.
Specifically, I'd be interested in your ideas on the following:
* Can I speed this up? If so, how much? If the pots are dry, is there
danger of breakage, if firing too fast? (Quartz inversion and all that?)
* Do I need to keep the lid propped open in the first part of the cycle?
(I do so because somebody, long ago, told me that one needs to let the
chemical water escape: Is this true?)
Thanks in advance!
Bob
Southern Oregon
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Bob Johnson on sun 30 dec 07
Does anyone have suggestions on an efficient bisque firing schedule for a smallish electric kiln (an old Cress B-29-H, with a capacity of about 17" x 22")? I have lost the manual, so I don't know any more the exact firing schedule the manufacturer recommended. And I have always suspected that I was firing too conservatively and using too much energy. What I usually do is this:
* Turn it on low with the lid open about 1-1/2" for a couple of hours.
* Turn up to medium for 2 more hours, with the lid open to the first notch (about 1/2")
* Turn to high, close the lid, insert the peep-hole plugs, and continue firing until the sitter turns it off---usually about 3 more hours.
Specifically, I'd be interested in your ideas on the following:
* Can I speed this up? If so, how much? If the pots are dry, is there danger of breakage, if firing too fast? (Quartz inversion and all that?)
* Do I need to keep the lid propped open in the first part of the cycle? (I do so because somebody, long ago, told me that one needs to let the chemical water escape: Is this true?)
Thanks in advance!
Bob
Southern Oregon
Maggie Jones on mon 31 dec 07
A while back someone suggested holding a small mirror over the top peep
to detect steam while the kiln is still on low. It works like a charm.
No steam means its ready to go up to medium. I have learned over the yrs
with the smaller kilns that if there is any steam in there, things blow
up 15 min after going up to medium!
Maggie
On Sun, 30 Dec 2007 20:06:53 -0500 Keba M Hitzeman
writes:
> Bob,
>
> With my little Olympic electric kiln, I bisque:
>
> Low, propped open - 45 minutes
> Low, lid closed - 1 hour
> Medium - 1 hr. 30 min
> High - until it trips.
>
> This is what my friends at the local pottery shop suggested, and it
> has
> worked very well for me. I have an under-kiln Ventmaster to the
> outside, so
> I leave all the peeps in during the firing.
>
> Keba
>
>
> ====================================
>
> Keba Hitzeman
> Dayton OH
>
> Spanish - http://keba.hitzeman.com
> Clay - http://yellowroomarts.blogspot.com
> Coffee - coffee@enigma22.com
>
> "The only thing necessary for the triumph of evil is for good men to
> do
> nothing"
> - Edmund Burke
>
>
> -----Original Message-----
> From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Bob
> Johnson
> Sent: Sunday, December 30, 2007 19:07
> To: CLAYART@LSV.CERAMICS.ORG
> Subject: questions on efficient bisque firing
>
> Does anyone have suggestions on an efficient bisque firing schedule
> for a
> smallish electric kiln (an old Cress B-29-H, with a capacity of
> about 17" x
> 22")? I have lost the manual, so I don't know any more the exact
> firing
> schedule the manufacturer recommended. And I have always suspected
> that I
> was firing too conservatively and using too much energy. What I
> usually do
> is this:
> * Turn it on low with the lid open about 1-1/2" for a couple of
> hours.
> * Turn up to medium for 2 more hours, with the lid open to the
> first
> notch (about 1/2")
> * Turn to high, close the lid, insert the peep-hole plugs, and
> continue
> firing until the sitter turns it off---usually about 3 more hours.
> Specifically, I'd be interested in your ideas on the following:
> * Can I speed this up? If so, how much? If the pots are dry, is
> there
> danger of breakage, if firing too fast? (Quartz inversion and all
> that?)
> * Do I need to keep the lid propped open in the first part of the
> cycle?
> (I do so because somebody, long ago, told me that one needs to let
> the
> chemical water escape: Is this true?)
> Thanks in advance!
>
> Bob
> Southern Oregon
>
>
_________________________________________________________________________
___
> __
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change
> your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
>
_________________________________________________________________________
_____
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change
> your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
>
Mike Gordon on mon 31 dec 07
Bob,
I don't see any reason to change your schedule if your not having any
cracks or things blowing up. Put a mirror in front of the top peep
hole, or over the opening of the lid, and see if there is moisture fog
on it. That will tell you if there is still moisture in the clay.
Electricity is cheap compared to losing a kiln load to save a few $ on
electricity. I have a Cress that size but I only do low fire glaze in
it. I'll look for the manual later today & let you know. Mike Gordon
On Dec 30, 2007, at 4:07 PM, Bob Johnson wrote:
> Does anyone have suggestions on an efficient bisque firing schedule
> for a smallish electric kiln (an old Cress B-29-H, with a capacity of
> about 17" x 22")? I have lost the manual, so I don't know any more the
> exact firing schedule the manufacturer recommended. And I have always
> suspected that I was firing too conservatively and using too much
> energy. What I usually do is this:
> * Turn it on low with the lid open about 1-1/2" for a couple of
> hours.
> * Turn up to medium for 2 more hours, with the lid open to the
> first notch (about 1/2")
> * Turn to high, close the lid, insert the peep-hole plugs, and
> continue firing until the sitter turns it off---usually about 3 more
> hours.
> Specifically, I'd be interested in your ideas on the following:
> * Can I speed this up? If so, how much? If the pots are dry, is
> there danger of breakage, if firing too fast? (Quartz inversion and
> all that?)
> * Do I need to keep the lid propped open in the first part of the
> cycle? (I do so because somebody, long ago, told me that one needs to
> let the chemical water escape: Is this true?)
> Thanks in advance!
>
> Bob
> Southern Oregon
>
> _______________________________________________________________________
> _______
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, or change
> your
> subscription settings here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
Bob Johnson on tue 1 jan 08
Thanks to everyone who had some thoughts on this.
In fact, I had been using the "mirror method" that several of you suggested, although I was getting some indication of water even when the temp got well over 400 degrees. I assume this is chemical water or, perhaps, atmospheric condensation from the studio. I still don't understand this, but it must not make too much difference. And I don't quite know where the chemical water goes, if the lid is closed and the peep plugs are in.
I think what I will do in the future is check the temp with a pyrometer and, over ~ 400 or so, just turn it up to high.
Happy New Year to all!
Bob
---in Southern Oregon
At 1/1/2008 01:15 PM, Snail Scott wrote:
>>-----Original Message-----
>>From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Bob
>>Johnson
>>Sent: Sunday, December 30, 2007 19:07
>>Does anyone have suggestions on an efficient bisque firing schedule...
>
>
>The critical phase is driving off the water through the lower
>temperatures. Getting to - and through - the 200 F mark is
>where slowness and caution are rewarded. Once you are
>past the first 400 degrees or so, you can go pretty quickly
>and smoothly up. If you go too fast, you'll have to do a long
>soak to make up for it, since you want to be sure to have a
>nice clean burnout. How long it 'long enough' depends
>entirely on your clay, though: some clay bodies are 'dirtier'
>than others, and need more burnout time. Quartz inversion
>is of very little concern when firing greenware. It's mainly an
>issue when firing (and cooling) high-fired clay.
>
>I like a nice long candling period, and (on my manual kiln)
>I set the top ring to low with the lid propped open about
>the thickness of a brick. I start this in late evening and then
>begin firing in earnest the next morning. Really, this is
>longer than necessary, even for my thick handbuilt work,
>but I'll use the extra power (not a lot on one-ring-low) and
>by candling overnight, I can be sure the kiln will reach
>temperature conveniently during working time the next day.
>
>In the morning, I shut the lid and leave it for about a half-hour
>to let the temperature equalize a bit, then turn the remaining
>rings to low and wait an hour. I give it usually no more than
>a half-hour on medium, then straight to high. It doesn't heat
>so quickly that I worry much about going too fast - in most
>electric kilns it's just not possible. I don't bother leaving a
>peephole open, since I figure the gaps around my lid give
>a similar amount of ventilation in a more distributed way. ;-)
>
>My own candling schedule is based on my own convenience,
>and thinly-thrown work of coarse clay may need no more
>than an hour of candling. Tighter clay bodies, thicker work,
>and damp clay will require proportionately more time.
>
>You are wasting energy leaving the lid propped open after
>the first hour or so - a peep (or a gap) is plenty of venting
>for any remaining moisture. Greenware breakage, in my
>experience, is always caused by moving too quickly past
>the 200-degree mark, never due to firing too fast thereafter.
>Incomplete burnout will show up in glaze defects later on,
>but most electric kilns (if loaded even moderately full) just
>don't fire fast enough for that to be much of a problem.
>
>In my opinion, 'medium' only exists to cushion the shock to
>the elements of suddenly being turned to 'high'; it's not really
>a necessary step for firing. I mainly use the 'medium' setting
>to even out an uneven glaze firing, turning any section that's
>hotter than the rest down to 'medium' until it all even out,
>and I can turn it all to high to finish up. I also use 'medium'
>to control the rate of cooling, by turning everything to
>'medium' after my cones read the proper heat-work, letting
>my matte glazes develop as I wish. I seldom spend much
>time on 'medium' otherwise. I don't know it anyone out there
>shares my opinion on this, but it works for me.
>
>Spend the extra time on low power, up to about 400 degrees,
>but then kick it into gear.
>
> -Snail
>
>______________________________________________________________________________
>Clayart members may send postings to: clayart@lsv.ceramics.org
>
>You may look at the archives for the list, post messages, or change your
>subscription settings here: http://www.acers.org/cic/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Snail Scott on tue 1 jan 08
> -----Original Message-----
> From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Bob
> Johnson
> Sent: Sunday, December 30, 2007 19:07
> Does anyone have suggestions on an efficient bisque firing schedule...
The critical phase is driving off the water through the lower
temperatures. Getting to - and through - the 200 F mark is
where slowness and caution are rewarded. Once you are
past the first 400 degrees or so, you can go pretty quickly
and smoothly up. If you go too fast, you'll have to do a long
soak to make up for it, since you want to be sure to have a
nice clean burnout. How long it 'long enough' depends
entirely on your clay, though: some clay bodies are 'dirtier'
than others, and need more burnout time. Quartz inversion
is of very little concern when firing greenware. It's mainly an
issue when firing (and cooling) high-fired clay.
I like a nice long candling period, and (on my manual kiln)
I set the top ring to low with the lid propped open about
the thickness of a brick. I start this in late evening and then
begin firing in earnest the next morning. Really, this is
longer than necessary, even for my thick handbuilt work,
but I'll use the extra power (not a lot on one-ring-low) and
by candling overnight, I can be sure the kiln will reach
temperature conveniently during working time the next day.
In the morning, I shut the lid and leave it for about a half-hour
to let the temperature equalize a bit, then turn the remaining
rings to low and wait an hour. I give it usually no more than
a half-hour on medium, then straight to high. It doesn't heat
so quickly that I worry much about going too fast - in most
electric kilns it's just not possible. I don't bother leaving a
peephole open, since I figure the gaps around my lid give
a similar amount of ventilation in a more distributed way. ;-)
My own candling schedule is based on my own convenience,
and thinly-thrown work of coarse clay may need no more
than an hour of candling. Tighter clay bodies, thicker work,
and damp clay will require proportionately more time.
You are wasting energy leaving the lid propped open after
the first hour or so - a peep (or a gap) is plenty of venting
for any remaining moisture. Greenware breakage, in my
experience, is always caused by moving too quickly past
the 200-degree mark, never due to firing too fast thereafter.
Incomplete burnout will show up in glaze defects later on,
but most electric kilns (if loaded even moderately full) just
don't fire fast enough for that to be much of a problem.
In my opinion, 'medium' only exists to cushion the shock to
the elements of suddenly being turned to 'high'; it's not really
a necessary step for firing. I mainly use the 'medium' setting
to even out an uneven glaze firing, turning any section that's
hotter than the rest down to 'medium' until it all even out,
and I can turn it all to high to finish up. I also use 'medium'
to control the rate of cooling, by turning everything to
'medium' after my cones read the proper heat-work, letting
my matte glazes develop as I wish. I seldom spend much
time on 'medium' otherwise. I don't know it anyone out there
shares my opinion on this, but it works for me.
Spend the extra time on low power, up to about 400 degrees,
but then kick it into gear.
-Snail
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