Pamela Regentin on wed 21 feb 07
I just got a used West Coast updraft installed. It has eight atmospheric burners. Since there is no way to candle the kiln I was trying to figure out how to preheat. It looked like I'd have to set up a separate little burner of some kind (to stick up through a burner port) and to do that with a safety shut off, etc. it was going to cost upwards of $300. Just to preheat. Then I got advice from Clayart in Tacoma to forget about the preheat if everything was bisqued. I had intended to do a bisque in the updraft but scrapped it. So I have high fired once and I started by having the gas on as low as possible (scant 1/4") door open and tried to warm up slowly for 2-3 hours.
Mel, do you think this is sufficiently slowly enough for a preheat that spares the furniture, etc.? I definately need to protect my investment but it seems overkill to set up a preheat flame that will be so costly.
Thanks,
Pam
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Tom King on wed 21 feb 07
Good Morning people,
Firing a Propane downdraft to cone ten and have
thought it would be great to have this thing
above 300 F when I get started in the morning.
Kiln is 23 sf insulators/fiber fired by two
Ransome B3s (venturi) Cold to ten is 10 hrs. +/-
I was headed for a preheat setup until two
recent posts caught my attention:
1) someone said that their preheat burner gave them
a 600 degree variance top to bottom.
2) An old post of Mark Wards said that he thought
a preheat is a waste of time. I know he sells
one but I won't hold that against him. Opinion
may still stand.
I have seen Mels post about scrounging your own baso
and am leaning that way.
Any feedback on this would be appreciated. Thanks.
Be Well,
Tom King
Threereeds1@cox.net
Megan Mason on wed 21 feb 07
It is possible preheat is a waste of fuel, but I would have two Eclipse
burners piggy back on my blower powered propane gas burners ,one each
side of the chimney on the back. I set the 45cuft sprung arch downdraft
kiln one day, and when bricked up, put it on preheat for overnight by 8 pm
and settting them on low until near midnight, then full from then on. At 6 am
next morning, I turned the big boys on and stated firing and had a cherry
red glow in the entire kiln at that point.My firing in the summer was at body
reduction by dusk and ended up cone 10 down tip only by 10-11 pm and had
less than 1/2 cone difference at bottom,if at all.
I used the kilnshelf on the chimney and bricks in the door to vary the rise
as well as the air/fuel .I used witness cones at 3 levels, minimum and front
and back,one-two for body reduction and 3-4 for final glaze readings. I
am sure with the new devices there are more efficient firing methods.
Meg
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Lee Love on thu 22 feb 07
My woodkiln holds heat pretty good after it is closed up. I have
pre-heated with wood up to 300 or 400, closed it up and it is still
over 200*F in the morning.
Could you heat to a somewhat higher temp at night and just
shut the kiln up? Then you have no worries about burners going out
or anything while you sleep.
Because of some of these advantage in my current design,
when I build in Minnesota, even though I can't fire totally with
wood, where I will be living, I think I will put in fireboxes and air
ports for wood so I can do things like preheat and add wood at temp
after dark.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Jennifer Boyer on thu 22 feb 07
Hi Pam,
Remember that there are plenty of potters like me who don't preheat.
In fact the last time I DID preheat, one of my Crystars shelves
broke. I have fired my 40 cu ft downdraft propane kiln without
preheating for 30 years. Mark Ward sells burners and designs kilns
for a living and he doesn't suggest preheating. I try to keep my
initial temp rise to under 300/hr.
Jennifer
On Feb 22, 2007, at 1:45 AM, Pamela Regentin wrote:
> I just got a used West Coast updraft installed. It has eight
> atmospheric burners. Since there is no way to candle the kiln I was
> trying to figure out how to preheat. It looked like I'd have to set
> up a separate little burner of some kind (to stick up through a
> burner port) and to do that with a safety shut off, etc. it was
> going to cost upwards of $300. Just to preheat. Then I got advice
> from Clayart in Tacoma to forget about the preheat if everything
> was bisqued. I had intended to do a bisque in the updraft but
> scrapped it. So I have high fired once and I started by having the
> gas on as low as possible (scant 1/4") door open and tried to warm
> up slowly for 2-3 hours.
>
> Mel, do you think this is sufficiently slowly enough for a preheat
> that spares the furniture, etc.? I definately need to protect my
> investment but it seems overkill to set up a preheat flame that
> will be so costly.
>
> Thanks,
> Pam
>
*****************************
Jennifer Boyer
Thistle Hill Pottery
Montpelier, VT
http://thistlehillpottery.com
*****************************
William & Susan Schran User on thu 22 feb 07
On 2/22/07 1:45 AM, "Pamela Regentin" wrote:
> Mel, do you think this is sufficiently slowly enough for a preheat that s=
pares
> the furniture, etc.? I definately need to protect my investment but it s=
eems
> overkill to set up a preheat flame that will be so costly.
We don't preheat our gas fired kiln at school, turn it on and let it go.
Get to 1000=B0F in 2-3 hours.
We use Advancer shelves,
I was worried about shelves & thermal shock.
Folks at Smith-Sharpe calmed my fears.
As long as there is no direct flame on the shelves, it'll be ok.
Well into 2nd year of firing with these shelves, no problems
No pots, no shelves blown up.
Regarding a preheat in this West Coast Kiln - our Geil has a similar burner
arrangement - 8 burners underneath the kiln. Each burner has a shut off
valve. Do each of your burners have shutoffs? If so, you could simply light
two burners, opposite corners.
--=20
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Lee Love on thu 22 feb 07
On 2/22/07, Jennifer Boyer wrote:
> Mark Ward sells burners and designs kilns
> for a living and he doesn't suggest preheating.
Pete Pinnell, a glaze guru who makes incredible pots, had us all
rethinking candling at his workshop at Northern Clay Center.
Pete's thought was that going slow in the beginning was a waste of
time and energy. All the glaze work is done at higher temps and
that is where you should take your time.
A positive aspect of wood firing is that you normally can't rush
the kiln through 1100*C to 1300*C If you over stoke at 1100*c you
typically start loosing heat.
And related to traditional methods. New isn't always better.
It is one reason why our copies of the old Chinese glazes, using
industrial techniques, really don't hold a candle to the originals.
Sometimes, the process IS the secret.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
JoAnne Willemsen on thu 22 feb 07
To Lee Love,=0D=0A=0D=0AI spend about six hours preheating my wood fir=
e kiln the night before to about 700F, using wood in a "preheating cha=
mber" built expressly for that purpose. I close it up and then head f=
or bed. By morning the temperature has dropped to around 500F, all re=
ady to start climbing. I live in North Iowa (in the middle of nowhere=
) so my kiln has seen all kinds of nasty weather but ALWAYS preheats a=
bout the same, regardless of wind, rain or snow.=0D=0AHope this helps.=
..=0D=0A=0D=0AJo Anne Willemsen=0D=0AOld Oaks Pottery=0D=0A=0D=0A=0D=
=0A =
Pamela Regentin on thu 22 feb 07
Hi Jennifer,
Yes, I know that it is done but I'm wondering about the toll taken on the kiln and furniture as others have commented on. How slowly should the initial start-up go from cold? Do you go to 600* in only two hours and is that sufficiently safe for the kiln and furniture? Is this simply two schools of thought?
Thank you!
Pam
Jennifer Boyer wrote: Hi Pam,
Remember that there are plenty of potters like me who don't preheat.
In fact the last time I DID preheat, one of my Crystars shelves
broke. I have fired my 40 cu ft downdraft propane kiln without
preheating for 30 years. Mark Ward sells burners and designs kilns
for a living and he doesn't suggest preheating. I try to keep my
initial temp rise to under 300/hr.
Jennifer
On Feb 22, 2007, at 1:45 AM, Pamela Regentin wrote:
> I just got a used West Coast updraft installed. It has eight
> atmospheric burners. Since there is no way to candle the kiln I was
> trying to figure out how to preheat. It looked like I'd have to set
> up a separate little burner of some kind (to stick up through a
> burner port) and to do that with a safety shut off, etc. it was
> going to cost upwards of $300. Just to preheat. Then I got advice
> from Clayart in Tacoma to forget about the preheat if everything
> was bisqued. I had intended to do a bisque in the updraft but
> scrapped it. So I have high fired once and I started by having the
> gas on as low as possible (scant 1/4") door open and tried to warm
> up slowly for 2-3 hours.
>
> Mel, do you think this is sufficiently slowly enough for a preheat
> that spares the furniture, etc.? I definately need to protect my
> investment but it seems overkill to set up a preheat flame that
> will be so costly.
>
> Thanks,
> Pam
>
*****************************
Jennifer Boyer
Thistle Hill Pottery
Montpelier, VT
http://thistlehillpottery.com
*****************************
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Jennifer Boyer on thu 22 feb 07
I've been doing it this way a long time and my kiln is holding up
fine. I don't rush the first part of the firing. I start with
2 pilot burners for an hour
one burner on 2 lbs for an hour
two burners on 2 lbs for an hour
2.5 lbs for an hour
3 lbs for the rest of the firing
Most of my shelves I've had for about 15 years. I have a crack in one
of them. The kiln looks fine and there's nothing wrong with any of
the posts. I don't see a problem. But there are lots of opinions out
there, lots of ways to do it...
Take Care
Jennifer
On Feb 22, 2007, at 3:43 PM, Pamela Regentin wrote:
> Hi Jennifer,
>
> Yes, I know that it is done but I'm wondering about the toll taken
> on the kiln and furniture as others have commented on. How slowly
> should the initial start-up go from cold? Do you go to 600* in only
> two hours and is that sufficiently safe for the kiln and
> furniture? Is this simply two schools of thought?
>
> Thank you!
> Pam
>
>
> Jennifer Boyer wrote: Hi Pam,
> Remember that there are plenty of potters like me who don't preheat.
> In fact the last time I DID preheat, one of my Crystars shelves
> broke. I have fired my 40 cu ft downdraft propane kiln without
> preheating for 30 years. Mark Ward sells burners and designs kilns
> for a living and he doesn't suggest preheating. I try to keep my
> initial temp rise to under 300/hr.
>
> Jennifer
> On Feb 22, 2007, at 1:45 AM, Pamela Regentin wrote:
>
>> I just got a used West Coast updraft installed. It has eight
>> atmospheric burners. Since there is no way to candle the kiln I was
>> trying to figure out how to preheat. It looked like I'd have to set
>> up a separate little burner of some kind (to stick up through a
>> burner port) and to do that with a safety shut off, etc. it was
>> going to cost upwards of $300. Just to preheat. Then I got advice
>> from Clayart in Tacoma to forget about the preheat if everything
>> was bisqued. I had intended to do a bisque in the updraft but
>> scrapped it. So I have high fired once and I started by having the
>> gas on as low as possible (scant 1/4") door open and tried to warm
>> up slowly for 2-3 hours.
>>
>> Mel, do you think this is sufficiently slowly enough for a preheat
>> that spares the furniture, etc.? I definately need to protect my
>> investment but it seems overkill to set up a preheat flame that
>> will be so costly.
>>
>> Thanks,
>> Pam
>>
>
> *****************************
> Jennifer Boyer
> Thistle Hill Pottery
> Montpelier, VT
> http://thistlehillpottery.com
> *****************************
>
> ______________________________________________________________________
> ________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
>
>
> ---------------------------------
> Don't be flakey. Get Yahoo! Mail for Mobile and
> always stay connected to friends.
>
> ______________________________________________________________________
> ________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
*****************************
Jennifer Boyer
Thistle Hill Pottery
Montpelier, VT
http://thistlehillpottery.com
*****************************
Erik Harmon on fri 23 feb 07
Its an amazing, dramatic, and sometimes painful lesson to balance the fuel and air intake needs on a wood kiln and how its needs change as the firing proceeds. Its a wonderful thing. Erik
sacredclay wrote: aspect of wood firing is that you normally can't rush
> the kiln through 1100*C to 1300*C If you over stoke at 1100*c you
> typically start loosing heat.
>
>
> --
> Lee in Mashiko, Japan>
Why does that happen, the losing of the heat? I'd thought it would get
hotter until you stop feeding the kiln wood. Kathryn in NC
______________________________________________________________________________
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Lee Love on fri 23 feb 07
On 2/23/07, sacredclay wrote:
> aspect of wood firing is that you normally can't rush
> > the kiln through 1100*C to 1300*C If you over stoke at 1100*c you
> > typically start loosing heat.
>
> Why does that happen, the losing of the heat? I'd thought it would get
> hotter until you stop feeding the kiln wood. Kathryn in NC
Heat is a combination of fuel and oxygen. If you have too much
fuel, you loose heat because there isn't enough oxygen to burn the
fuel. The biggest problem folks new to woodfiring make is putting
too much wood in the firebox precicely because they think more fuel =
more heat. It is like pumping the gas pedal when your car is
flooded.
In my kiln, at 1100*C, you back off from 2kgs a stoke to 1.5kgs if
you want the heat to keep raising. When you get to around cone 8/9
you can go back to 2kgs.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Lee Love on fri 23 feb 07
On 2/23/07, Erik Harmon wrote:
> Its an amazing, dramatic, and sometimes painful lesson to balance the fuel and air intake
> needs on a wood kiln and how its needs change as the firing proceeds. Its a
>wonderful thing. Erik
Yes, unlike an electric kiln, you have to listen to what the kiln
needs. Rather than "mastering" a wood kiln, you learn to communicate
with it.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Erik Harmon on fri 23 feb 07
Lee Love wrote: Heat is a combination of fuel and oxygen. If you have too much
fuel, you loose heat because there isn't enough oxygen to burn the
fuel. The biggest problem folks new to woodfiring make is putting
too much wood in the firebox precicely because they think more fuel =
more heat. It is like pumping the gas pedal when your car is
flooded.
In my kiln, at 1100*C, you back off from 2kgs a stoke to 1.5kgs if
you want the heat to keep raising. When you get to around cone 8/9
you can go back to 2kgs.
Lee,
How rapidly are you stoking. Do you increase the amount air you allow in at some point or do you find that air is pretty stable the whole time and temperature gain just gradually builds. Also what kind of a damper system do you use.
Erik
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Lee Love on fri 23 feb 07
On 2/23/07, JoAnne Willemsen wrote:
>nasty weather but ALWAYS preheats about the same, regardless of wind,
rain or snow.
> Hope this helps...
Sometimes "old" is better than new isn't it? Don't have to be a
Luddite to recognize this. ;^)
Many of the "fixes" for electric kiln firing are simply making the
kiln behave like traditional kilns always have. But our prejudices
for "new" and "advanced" hold us back.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
sacredclay on fri 23 feb 07
aspect of wood firing is that you normally can't rush
> the kiln through 1100*C to 1300*C If you over stoke at 1100*c you
> typically start loosing heat.
>
>
> --
> Lee in Mashiko, Japan>
Why does that happen, the losing of the heat? I'd thought it would get
hotter until you stop feeding the kiln wood. Kathryn in NC
sacredclay on sat 24 feb 07
In rereading this post, I realized that I have no idea what kgs means.
Can you throw that one in too? Tahnks! Kathryn
> In my kiln, at 1100*C, you back off from 2kgs a stoke to 1.5kgs if
> you want the heat to keep raising. When you get to around cone 8/9
> you can go back to 2kgs.
>
>
>
> Lee,
>
>
Lee Love on sat 24 feb 07
On 2/24/07, sacredclay wrote:
> In rereading this post, I realized that I have no idea what kgs means.
> Can you throw that one in too? Tahnks! Kathryn
kilograms
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
Ivor and Olive Lewis on sat 24 feb 07
Lee Love made the following comment <through 1100*C to 1300*C If you over stoke at 1100*c you typically start =
loosing heat.>
Kathryn asked <thought it would get hotter until you stop feeding the kiln wood .>>
The key words are "Over stoke" which means adding excess fuel. It could =
apply equally well to Oil or Gas firing. If you add more fuel than can =
be consumed by available air entering the chamber you prevent burning =
due to back pressure from the gases being evolved. Air is prevented from =
getting into the chamber, so no heat generation giving time for cooling =
to start.
The cures are to open the damper wider, which may not be possible or =
restrict fuel flow to an optimum rate.
Best regards
Ivor Lewis.
Redhill,
South Australia.
Lee Love on sat 24 feb 07
On 2/24/07, Erik Harmon wrote:
> How rapidly are you stoking.
About every 7 minutes. But when you use less wood, you usually
have to stoke more often.
>Do you increase the amount air you allow in at some point or do you
find that air is pretty
> stable the whole time and temperature gain just gradually builds. Also what kind of a
>damper system do you use.
I usually only close the damper more, otherwise, you only
get oxidation. In the type of kiln I have, the fireboxes are open,
so there is a lot of air available.
I have a shelf in the chimney, but I also have a passive
damper in the front under the door, some bricks in the flue channel.
I start with the damper at 1/2 closed but do not close it more than
3/4ths.
--
Lee in Mashiko, Japan
Minneapolis, Minnesota USA
http://potters.blogspot.com/
"To affect the quality of the day, that is the highest of arts." -
Henry David Thoreau
"Let the beauty we love be what we do." - Rumi
John Rodgers on mon 26 feb 07
Tom,
I - among others - used to operate a 90 CU FT Minnesota Flattop out west
at 6,000 feet ASL or thereabouts. Used natural gas. We would candle the
kiln all night on the pilot lights, with the fans running, then at 4 am
in the morning, the burners would kick in on low as they were on timers
and solenoid valves. By the time people got to work at 7 am the kiln was
up to 1500 degrees. It would finish in the early to late afternoon,
depending on the load. The kiln was well adjusted and rarely were there
problems with cold or hot spots. That kiln never stalled even once
while I was there, and I was not the only operator. Reduction was
always good.
The one thing that made a big difference in performance was when we
changed out the straight line gas to the burners and installed that
calibrated orifice. That made a huge difference in our ability to fine
tune the fuel flow for best burn. Were I to build a gas kiln myself, I
would include the calibrated orifice from the get-go. It was a bit
expensive - like $175 as I remember - but worth every penny. I would
think it would also be appropriate to propane fired kilns as well.- that
have two or more burners.
Preheating does work. I would expect it to have it's greatest
efficiences in larger kilns, however, simply because of the greater mass
inside that must be heated.
Regards,
John Rodgers
Tom King wrote:
> Good Morning people,
>
> Firing a Propane downdraft to cone ten and have
> thought it would be great to have this thing
> above 300 F when I get started in the morning.
>
> Kiln is 23 sf insulators/fiber fired by two
> Ransome B3s (venturi) Cold to ten is 10 hrs. +/-
>
> I was headed for a preheat setup until two
> recent posts caught my attention:
>
> 1) someone said that their preheat burner gave them
> a 600 degree variance top to bottom.
>
> 2) An old post of Mark Wards said that he thought
> a preheat is a waste of time. I know he sells
> one but I won't hold that against him. Opinion
> may still stand.
>
> I have seen Mels post about scrounging your own baso
> and am leaning that way.
>
> Any feedback on this would be appreciated. Thanks.
>
> Be Well,
> Tom King
>
> Threereeds1@cox.net
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots@pclink.com.
>
>
>
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