Ingeborg Foco on thu 7 jan 10
I fired the dragon today. Mine is a downdraft and I have bag walls (two
burners on each side). I spent a lot of time today going thru my extensive
library searching bag walls. (I have been adjusting my bag walls in hopes o=
f
improving my firing results and shortening my firing times) It is
interesting that little is said about them except they are to deflect the
flame. Nothing about how high, the ratio to the size of the kiln, flue etc=
.
or anything else.
So, I ask, are there any bag wall experts out there. What is the optimum
height of a bag wall in relation to the interior kiln box. Is there a
formula that can generally be followed? I wasn't able to find much of
anything.
On a side note, my Fluke meter crapped out on me and I was literally workin=
g
in the dark: Something like Bob Dylan's song the name eludes me right at
this time something about figuring the mysteries of life/sex and working it
out in the dark ...that's not it but some of you might know the song if you
are old enough. I digress, I was working in the dark without a pyrometer o=
r
my beloved fluke dual read meter. Wow, it was like going back to the dark
ages. Only tomorrow will I know what actually happened. Just going by the
smell of the kiln and the drop of the cones, nothing else.
Ingeborg
--
Sincerely,
Ingeborg
http://www.thepottersworkshop.com
Steve Mills on fri 8 jan 10
Ingeborg
Bag walls unfortunately are the one item in a kiln where there appear to be
no rules, only seatofthepants stuff.
My approach with any new Gas kiln I build is to start without any, working
on the basis that flame path is going to be dictated by the way I pack it,
not by erecting barriers/deflectors.
The only time I have put them in was with my last production Kiln
(Downdraught 55 Cu Ft Gross) which was fired by two horizontally opposed
burners. I experienced a small amount of burn-out on a few wares located at
the point where the flames lifted out of the troughs. I cured that with 6
bricks on each side in an open chequer right at the end of each trough. If
the troughs had been a bit deeper I suspect that would not have been needed=
.
Steve M
2010/1/8 Ingeborg Foco
> I fired the dragon today. Mine is a downdraft and I have bag walls (two
> burners on each side). I spent a lot of time today going thru my extensi=
ve
> library searching bag walls. (I have been adjusting my bag walls in hopes
> of
> improving my firing results and shortening my firing times) It is
> interesting that little is said about them except they are to deflect the
> flame. Nothing about how high, the ratio to the size of the kiln, flue
> etc.
> or anything else.
>
> So, I ask, are there any bag wall experts out there. What is the optimum
> height of a bag wall in relation to the interior kiln box. Is there a
> formula that can generally be followed? I wasn't able to find much of
> anything.
>
> On a side note, my Fluke meter crapped out on me and I was literally
> working
> in the dark: Something like Bob Dylan's song the name eludes me right a=
t
> this time something about figuring the mysteries of life/sex and working =
it
> out in the dark ...that's not it but some of you might know the song if y=
ou
> are old enough. I digress, I was working in the dark without a pyrometer
> or
> my beloved fluke dual read meter. Wow, it was like going back to the dar=
k
> ages. Only tomorrow will I know what actually happened. Just going by t=
he
> smell of the kiln and the drop of the cones, nothing else.
>
> Ingeborg
>
>
>
>
>
> --
> Sincerely,
>
> Ingeborg
>
> http://www.thepottersworkshop.com
>
--
Steve
Bath
UK
www.mudslinger.me.uk
Loren JOnes on fri 8 jan 10
From my experience bag walls are perhaps unnecessary. When I started to lea=
=3D
rn how to fire a gas kiln it was with very little instruction. Trial by fir=
=3D
e if you will.Everyone I talked to had a different take.=3DA0The kiln had a=
b=3D
ag wall that went nearly half way up the interior of the kiln! The idea is =
=3D
that the higher the wall the more the flame has to work to get to the top o=
=3D
f the kiln. If you are having trouble with the=3DA0top being cold=3DA0you b=
uild=3D
it higher. Well, I didn't buy=3DA0that line of reasoning and tore the wall=
d=3D
own to=3DA0three=3DA0rows of brick.=3DA0Row one is solid, bricks=3DA0touchi=
ng. Next=3D
row they are spaced an inch or two apart the third row is half bricks spac=
=3D
ed 3 or 4 inches apart.This kiln=3DA0had two powered burners coming in from=
t=3D
he back of the kiln. I had a split set in the flame trough about 6 inches f=
=3D
rom the back to break up and deflect the flame.=3DA0The kiln fires just fin=
e,=3D
I tried adjusting the gap between the back wall of the kiln and the bottom
shelf to try and adjust for the cool spot. Never got that to go away. I tr=
=3D
y to put things back there that don't need alot of heat, iron oxide and suc=
=3D
h.=3DA0 I have had the opportunity to fire a number of kilns and have set u=
p =3D
the bag wall like that on all of them. Seems to work just fine. Best of luc=
=3D
k hope this helps, Loren=3D0Ahttp://www.lojoclayworks.com=3D0A=3D0A=3D0A=3D=
0A=3D0A_____=3D
___________________________=3D0AFrom: Ingeborg Foco M>=3D
=3D0ATo: Clayart@LSV.CERAMICS.ORG=3D0ASent: Thu, January 7, 2010 6:17:45 PM=
=3D0AS=3D
ubject: Bag Walls for downdraft kilns=3D0A=3D0AI fired the dragon today.=3D=
A0 Min=3D
e is a downdraft and I have bag walls (two=3D0Aburners on each side).=3DA0 =
I sp=3D
ent a lot of time today going thru my extensive=3D0Alibrary searching bag w=
al=3D
ls. (I have been adjusting my bag walls in hopes of=3D0Aimproving my firing=
r=3D
esults and shortening my firing times)=3DA0 It is=3D0Ainteresting that litt=
le i=3D
s said about them except they are to deflect the=3D0Aflame.=3DA0 Nothing ab=
out =3D
how high, the ratio to the size of the kiln, flue etc.=3D0Aor anything else=
.=3D
=3D0A=3D0ASo, I ask, are there any bag wall experts out there.=3DA0 What is=
the o=3D
ptimum=3D0Aheight of a bag wall in relation to the interior kiln box.=3DA0 =
Is t=3D
here a=3D0Aformula that can generally be followed?=3DA0 I wasn't able to fi=
nd m=3D
uch of=3D0Aanything.=3D0A=3D0AOn a side note, my Fluke meter crapped out on=
me an=3D
d I was literally working=3D0Ain the dark:=3DA0 Something like Bob Dylan's =
song=3D
=3DA0 the name eludes me right at=3D0Athis time something about figuring th=
e my=3D
steries of life/sex and working it=3D0Aout in the dark ...that's not it but=
s=3D
ome of you might know the song if you=3D0Aare old enough.=3DA0 I digress, I=
was=3D
working in the dark without a pyrometer or=3D0Amy beloved fluke dual read =
me=3D
ter.=3DA0 Wow, it was like going back to the dark=3D0Aages.=3DA0 Only tomor=
row wi=3D
ll I know what actually happened.=3DA0 Just going by the=3D0Asmell of the k=
iln =3D
and the drop of the cones, nothing else.=3D0A=3D0AIngeborg=3D0A=3D0A=3D0A=
=3D0A=3D0A=3D0A--=3D
=3D0ASincerely,=3D0A=3D0AIngeborg=3D0A=3D0Ahttp://www.thepottersworkshop.co=
m=3D0A=3D0A=3D0A=3D
=3D0A
Lee Love on fri 8 jan 10
On Thu, Jan 7, 2010 at 7:17 PM, Ingeborg Foco wro=
=3D
te:
> I fired the dragon today. =3DA0Mine is a downdraft and I have bag walls (=
tw=3D
o
> burners on each side).
Ingeborg, Which way do your burners point?
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Vince Pitelka on fri 8 jan 10
Ingebord -
The only circumstance in which you need bagwalls in a downdraft or updraft
kiln is when the burner ports are in the side walls and the flames would
otherwise impinge directly on the wares. In that case, the normal model is
to have a solid row of bricks at the level of the burner ports, and then as
checkered (alternating gaps between bricks) wall for two more layers. In a
kiln where the bottom tends to fire cold, some people will place a brick in
front of each burner port, but then leave some gaps even in the first layer=
.
There is no hard and fast rule other than keeping the flames from impinging
directly on the wars, and this is something that must be tuned to your
particular kiln.
In kilns where the burner ports are on the outer edges of the front or back
wall, so that the flames are directed in along the side walls and are not
aimed at the ware, there is no need for bagwalls. The same is true of a
kiln where the burners ports are in the floor at the outer edges of the
interior, and the flames rise along the inner walls.
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net; wpitelka@tntech.edu
http://iweb.tntech.edu/wpitelka
Ingeborg Foco on fri 8 jan 10
Hi All,
Thanks all for the input. I should have given you more info so here's the
story:
I've been having problems with one burner pumping out a lot of soot. This
has been going on for a while and finally figured out it's the lizards that
climb in and plug things up. I now have a thorough inspection of the four
burners (taking them apart and getting the miserable critters out of there
before each firing ) that worked but I still have a sooting problem. I
have taken the pipes apart thinking something is constricting...clean as a
whistle. So now I am messing with the bag walls as well as the burner
orifices Is that the plural of orifice?
I tend to have a cold spot by the flue exit and often the entire shelf is
much colder than the rest of the kiln. Yesterdays firing ^9 didn't even
bend in that area. Everything on that shelf needs to be refired.
The middle seems to be hotter and the bottom is hot as well...top is cooler=
.
Lauren, I would not take the bag walls out completely and here's my reason.
In the early 80's I bought an oxi probe from Nils Lou. It is also not
working! Everything seems to be falling apart. I drove to his place in
Oregon and he showed me his studio, his Minnesota flat top and told me to
get rid of my bag walls. He is very anti bag walls. The kiln I had was
much smaller but on the same idea as what I have now. I went home took th=
e
bag walls out and WOWE, the worst firing ever. Nils said I would save on
fuel consumption well guess what, I used an unbelievable amount of fuel for
that little kiln. So, my take on that is when you have a downdraft with
side burners you need bag walls to deflect and direct the flame.
The question is how high a bag wall and the spaces in between the bricks.
Hank, I will try your suggestions and hopefully that will solve the cold
spot and the sooting. And I think the Bob Dylan song was "Night Moves"
Thanks
Ingeborg
> So, I ask, are there any bag wall experts out there. What is the optimum
> height of a bag wall in relation to the interior kiln box. Is there a
> formula that can generally be followed? I wasn't able to find much of
> anything.
>
>
>
>
>
>
>
>
> --
> Sincerely,
>
> Ingeborg
>
> http://www.thepottersworkshop.com
>
Ingeborg Foco on sat 9 jan 10
David, Hank and all,
Please accept my apology for making you all fly all over the place. I
always seem to be on the run and trying to get lots of things done. Sorry.
As for Nils and my visit to his studio. I would be very foolish to claim
"he said she said" of something that transpired most likely 25 years ago.
He is very much against bag walls and I reread his book today at the shop.
He does say if you have side burners to have a couple of target bricks set
up to deflect the flame from the wares but states bag walls are a waste of
energy.
The sooting, well at first it was the lizards but I have that sort of under
control. (they can still climb in there during the firing since the air
plates stay relatively cool and I am now onto them and have figured that
out. I shut that burner down, get the bugger out with long tweezers and
proceed with the firing)
This kiln lived in Camas, Washington for a number of years. It was situate=
d
high on a hill top and worked quite well with only about 1/2 cone differenc=
e
from top to bottom or anywhere else. For me, 1/2 cone is good enough. In
other words, it functioned quite well. Then I moved to SW Florida.
I disassembled the kiln moved it to St. James City and reassembled it. All
of the bricks were numbered, lots of pictures taken and I am positive it i=
s
reassembled correctly. For whatever reason, it has never really been happy
here in SW Florida. I know the climate is different...hot humid, The
chimney is shorter than in Camas, there are no trees or walls to interfere
with the draft like in Camas which would seem like a plus. It has never
fired evenly from top to bottom since I've been here and I suspect I have
created some of the problems by twitching things trying to get it to run
like it used to. Does that make sense? In Camas, the top and middle were
the same cone and the bottom was a bit colder. Now the top is cold, the
middle hot and the bottom kind of hot and everything else is always a crap
shoot. I place a lot of cone packs throughout the kiln.
I've always fired with propane so that isn't anything new. Please don't as=
k
me exactly what changes I've made. I take long and elaborate notes and the=
n
two months later I re read them and quite frankly can't make heads or tails
out of anything. I don't know it I am partially dyslexic or just plain
inept. Could be a little bit of both. I have adjusted the orifices, the
bag walls and well that's really it. What else is there.
I've tried to adjust the burners acoustically, but honestly even though my
hearing is good, it is hard for me to distinguish a difference in the
pitch. I look at the flame to see if I'm getting a good burn and I've
adjusted the burners by testing time/temp with a volt meter. I hope I'm
explaining this so it makes sense to you.
At this point, I think I should try Hank and Shane's suggetion and work wit=
h
the bag wall some more.
Ingeborg
On Sat, Jan 9, 2010 at 2:58 AM, David Woof wrote:
> Hi Ingeborg,
>
> you are right, the "whole story" helps form an on target reply. You had
> folks flying off like a flock of disoriented canada geese.
>
>
>
> Respectfully, Did you tell Nils that you had side burners? I'm betting
> Nils told you more than just to take out the bag walls and that you may h=
ave
> forgotten or disregarded the part about size of exit flue and stack as we=
ll
> as his nifty double venturi at the base of the stack. (Understand the
> principal of the venturi effect before building one.)
>
>
>
> It is just common sense to put in a target/baffle/diffusing brick for sid=
e
> burners to prevent direct impingement on the "target pots".. too much baf=
fle
> however and one back pressures the burners causing sooting or
> failure/premature burnout damage to the burners.
>
>
>
> In my experience those cold spots you refer to are usually the consequenc=
e
> of too large an exit opening. Nils is adamant that restriction there cau=
ses
> turbulence in the gasses attempting to exit and so mixes the kiln atmosph=
ere
> at this point thus evening the heat distribution. He is proven right and=
he
> has a formula.
>
>
>
> I recently inspected a kiln that "didn't fire well at all". Fellow had
> taken out the bag wall and then placed the first shelf higher than the fl=
oor
> level exit flue with empty space below(no pots) and then was questioning =
the
> lack of a bag wall for the firing disaster. Pay better attention I gues=
s.
>
>
>
> In the back of my exit flue venturi box I build a door that allows me to
> reach in and fine tune this exit area by splitting the exit with a 1"x 4
> 1/2" x 9" brick stood on end and shaved to be loose enough to be turned o=
n a
> dusting of alumina as a vane to open or close this area a bit more or les=
s.
> I like to build in controls that I may never use but for just that one in
> ten year occasion of necessity I have this capability available.
>
>
>
> Same reason I always have a two bricks (4 1/2" x 9") hole at the front to=
p
> of a downdraft just in case I ever want to pull them to create an updraft
> condition to mix or move heat and atmosphere within the kiln.
>
>
>
> David Woof
>
>
>
>
>
David Woof on sat 9 jan 10
Hi Ingeborg=3D2C =3D20
you are right=3D2C the "whole story" helps form an on target reply. You had=
f=3D
olks flying off like a flock of disoriented canada geese.
=3D20
Respectfully=3D2C Did you tell Nils that you had side burners? I'm betting=
N=3D
ils told you more than just to take out the bag walls and that you may have=
=3D
forgotten or disregarded the part about size of exit flue and stack as wel=
=3D
l as his nifty double venturi at the base of the stack. (Understand the pr=
=3D
incipal of the venturi effect before building one.)
=3D20
It is just common sense to put in a target/baffle/diffusing brick for side =
=3D
burners to prevent direct impingement on the "target pots".. too much baffl=
=3D
e however and one back pressures the burners causing sooting or failure/pre=
=3D
mature burnout damage to the burners.
=3D20
In my experience those cold spots you refer to are usually the consequence =
=3D
of too large an exit opening. Nils is adamant that restriction there cause=
=3D
s turbulence in the gasses attempting to exit and so mixes the kiln atmosph=
=3D
ere at this point thus evening the heat distribution. He is proven right a=
=3D
nd he has a formula.
=3D20
I recently inspected a kiln that "didn't fire well at all". Fellow had tak=
=3D
en out the bag wall and then placed the first shelf higher than the floor l=
=3D
evel exit flue with empty space below(no pots) and then was questioning the=
=3D
lack of a bag wall for the firing disaster. Pay better attention I guess=
=3D
.
=3D20
In the back of my exit flue venturi box I build a door that allows me to re=
=3D
ach in and fine tune this exit area by splitting the exit with a 1"x 4 1/2"=
=3D
x 9" brick stood on end and shaved to be loose enough to be turned on a du=
=3D
sting of alumina as a vane to open or close this area a bit more or less. I=
=3D
like to build in controls that I may never use but for just that one in te=
=3D
n year occasion of necessity I have this capability available.=3D20
=3D20
Same reason I always have a two bricks (4 1/2" x 9") hole at the front top =
=3D
of a downdraft just in case I ever want to pull them to create an updraft c=
=3D
ondition to mix or move heat and atmosphere within the kiln.
=3D20
David Woof
=3D20
________________________________________________________________________
4a. Re: Bag Walls for downdraft kilns
Posted by: "Ingeborg Foco" ingeborg.foco@GMAIL.COM=3D20
Date: Fri Jan 8=3D2C 2010 3:33 pm ((PST))
=3D20
Hi All=3D2C
=3D20
=3D20
=3D20
Thanks all for the input. I should have given you more info so here's the
story:
=3D20
I've been having problems with one burner pumping out a lot of soot. This
has been going on for a while and finally figured out it's the lizards that
climb in and plug things up. I now have a thorough inspection of the four
burners (taking them apart and getting the miserable critters out of there
before each firing ) that worked but I still have a sooting problem. I
have taken the pipes apart thinking something is constricting...clean as a
whistle. So now I am messing with the bag walls as well as the burner
orifices Is that the plural of orifice?
=3D20
I tend to have a cold spot by the flue exit and often the entire shelf is
much colder than the rest of the kiln. Yesterdays firing ^9 didn't even
bend in that area. Everything on that shelf needs to be refired.
The middle seems to be hotter and the bottom is hot as well...top is cooler=
=3D
.
=3D20
Lauren=3D2C I would not take the bag walls out completely and here's my rea=
so=3D
n.
In the early 80's I bought an oxi probe from Nils Lou. It is also not
working! Everything seems to be falling apart. I drove to his place in
Oregon and he showed me his studio=3D2C his Minnesota flat top and told me =
to
get rid of my bag walls. He is very anti bag walls. The kiln I had was
much smaller but on the same idea as what I have now. I went home took the
bag walls out and WOWE=3D2C the worst firing ever. Nils said I would save o=
n
fuel consumption well guess what=3D2C I used an unbelievable amount of fuel=
f=3D
or
that little kiln. So=3D2C my take on that is when you have a downdraft with
side burners you need bag walls to deflect and direct the flame.
=3D20
The question is how high a bag wall and the spaces in between the bricks.
Hank=3D2C I will try your suggestions and hopefully that will solve the col=
d
spot and the sooting. And I think the Bob Dylan song was "Night Moves"
=3D20
Thanks
=3D20
Ingeborg
=3D20
> So=3D2C I ask=3D2C are there any bag wall experts out there. What is the =
opti=3D
mum
> height of a bag wall in relation to the interior kiln box. Is there a
> formula that can generally be followed? I wasn't able to find much of
> anything.
>Sincerely=3D20
=3D20
Ingeborg
=3D20
=3D20
_________________________________________________________________
Hotmail: Trusted email with powerful SPAM protection.
http://clk.atdmt.com/GBL/go/196390707/direct/01/=3D
Lee Love on sat 9 jan 10
Thanks for explaining the direction of your burners. If your
burners come in from the front or back, or face upward from the floor,
bagwalls are not so necessary.
What kind of burners do you have? Another variable is
the size of your burner ports. If they are large, a lot of secondary
air can come in through them.
Nice thing about a large flue exit, is that it is easy to make
smaller, by putting bricks in it.
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D97tha=
t is, "T=3D
he
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Jess McKenzie on sun 10 jan 10
This is a great List! We'd heard of spiders
sabatoging venturi burners. Now, we've learned of
lizard lurking. And we're grateful for the new
knowledge.
We'd like to reciprocate by sharing another "firing"-
related frustration we learned off-List. It's an
Alaska story:
One summer, an acquaintance in Fairbanks disassembled
his old Mercedes, and stored the engine parts in his
garage. In late fall, he entered the heated garage,
installed rings and other parts, reassembled the car,
and hit the starter.
The engine came to life. It purred like a big cat.
Then it stopped.
It refused to start again despite anything he tried.
After exhausting (a clue!) his mechanical repertory,
he happened to glance into a dark corner of the
garage. He noticed the large bag of popcorn. He saw
a hole in the bag. He saw the tiny tracks. ...
Eventually, he checked the muffler, to find it full
of white puffs of popsorn. He's certain that a
family of voles had used his muffler as a storage
bin. And once the muffler heated up ...
He still wonders why the voles didn't just leave the
corn in the bag until they needed it.
~joan and jess
in Sequim, where we have moles but no voles and only
a KS-1027 to guard.
........................
Ingeborg Foco wrote, in
part:
"... The sooting, well at first it was the lizards
but I have that sort of under control. (they can
still climb in there during the firing since
the air plates stay relatively cool and I am now onto
them and have figured that out. I shut that burner
down, get the bugger out with long tweezers and
proceed with the firing) ..."
Ingeborg Foco on sun 10 jan 10
Hi Jess,
What a great story.
Isn't it something the wild life we have to put up with:)
Here's another one: After getting my kiln installed and doing a late firin=
g
(in winter) I went to the kiln room to check the instruments and tweak the
burners and as I looked up from my log book there was a HUGE yellow snake
taking advantage of the warmth. I was new and didn't know the type of snak=
e
it was but fortunately there was a bug screen between me and him. I'm not
really afraid of snakes but didn't know if it was poisonous.
I quickly educated myself on snakes and found it to be a "rat" snake very
beneficial to the environment since the rats around here seem big enough to
carry off small potters:)
As for the lizards, tourists love them and often when I sell a vase and wra=
p
it, out roll the lizard eggs, I don't charge for them.
Ingeborg
On Sun, Jan 10, 2010 at 12:27 PM, Jess McKenzie wrote=
:
> This is a great List! We'd heard of spiders
> sabatoging venturi burners. Now, we've learned of
> lizard lurking. And we're grateful for the new
> knowledge.
>
> We'd like to reciprocate by sharing another "firing"-
> related frustration we learned off-List. It's an
> Alaska story:
>
> One summer, an acquaintance in Fairbanks disassembled
> his old Mercedes, and stored the engine parts in his
> garage. In late fall, he entered the heated garage,
> installed rings and other parts, reassembled the car,
> and hit the starter.
>
> The engine came to life. It purred like a big cat.
> Then it stopped.
>
> It refused to start again despite anything he tried.
> After exhausting (a clue!) his mechanical repertory,
> he happened to glance into a dark corner of the
> garage. He noticed the large bag of popcorn. He saw
> a hole in the bag. He saw the tiny tracks. ...
>
> Eventually, he checked the muffler, to find it full
> of white puffs of popsorn. He's certain that a
> family of voles had used his muffler as a storage
> bin. And once the muffler heated up ...
>
> He still wonders why the voles didn't just leave the
> corn in the bag until they needed it.
>
> ~joan and jess
> in Sequim, where we have moles but no voles and only
> a KS-1027 to guard.
> ........................
>
> Ingeborg Foco wrote, in
> part:
> "... The sooting, well at first it was the lizards
> but I have that sort of under control. (they can
> still climb in there during the firing since
> the air plates stay relatively cool and I am now onto
> them and have figured that out. I shut that burner
> down, get the bugger out with long tweezers and
> proceed with the firing) ..."
>
--
Sincerely,
Ingeborg
http://www.thepottersworkshop.com
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