Marcia Selsor on wed 8 apr 98
Dear Ellen,
I hope we can get some responses from high altitude firers. I have been using
natural draught burners for a long time. I am still convinced that one needs a
strong draught for control. I fire gas with the damper 1/2-1/4 (reduction)
open most of the time. The kilns are so controllable we have a mark on the
damper shelf for beginners to follow
when firing. To figure the natural draught as was mentioned on here several
years ago, I brun paper in the chimney and when the ashes fly up, I think it
is tall enough.
What do others think? It would be helpful to hear about many different
experiences with gas kilns. Where are the folks from Missoula or the Bray?
Marcia in Montana
Orion/Baker wrote:
>
> ----------------------------Original message----------------------------
> I saw Marcia's piece today saying that she needed to raise the height of a
> wood burning kiln's chimney in order to get it to draw at 6,000 ft. I
> didn't doubt her for a minute when she said that flames shot out the top --
> I'm sure that by speeding up the airflow, the entire combustion area got
> quite a hustle -- the entire flame got stretched forward (upstream), and I
> bet they really had to step up stoking speed to keep that dragon burning!
> (I love a good fire, and I bet it was a hoot!)
>
> But "thin air" is "thin air," and even fast moving or compressed thin air
> is still "thin" in terms of ratio of nitrogen:oxygen, etc. The higher you
> go in the mountains, the harder it is to keep any flame burning efficiently
> -- gas or wood. Beyond some altitudes, there may be no way that anyone can
> get their kiln up to full temperature -- no matter how hard they blow on
> the coals!
>
> What I was trying to share in the pieces I wrote about orifice sizing and
> gas through-put (draught), was an approach to making gas firing at altitude
> as efficient and controllable as possible, keeping as much heat in the kiln
> chamber as long as you can (the place where it will do the most good).
>
> I wonder how high (altitude) anyone's regularly done wood firing -- and
> how/if they could get to Cone 10, Cone 6, whatever...
>
> Best to all,
>
> Ellen Baker - Glacier, WA
> orion@telcomplus.net
Ben Shelton on thu 9 apr 98
A buddy of mine fires propane to ^10 at about 7800 ft. Until recently he
was using natural draft burners. Until recently though. For some as of yet
unexplained reason, his firings went bad. No reduction, bad draft..... So
he went to the hardware store and built four small forced air burners and
viola. Good reduction and even, fast firing. We still have no idead what
caused his kiln to fire differently after three years of great performance
but we tried almost everything to fix it including adding height to the
chimney. About 7ft added to total about 16ft. That failed so he went to
forced air. You may want to consider it....
Michelle H. Lowe on thu 9 apr 98
> To figure the natural draught as was mentioned on here several
>years ago, I brun paper in the chimney and when the ashes fly up, I think it
>is tall enough.
>What do others think? It would be helpful to hear about many different
>experiences with gas kilns. Where are the folks from Missoula or the Bray?
I'm not at high altitude but thought I'd lend my 2c
I have a 20 cu foot downdraft propane-fired car kiln here that I built in
early 1997. It's got a venturi flu and hardly any stack at all beyond the
top of the kiln. I read Nils book and when I first started firing it, I
thought I'd see how it fired before I built the stack up any higher, since
he says you don't need a stack to get draft with this type of flu, and the
kiln I based my design on has very little stack. Been firing it almost a
year now (next month). I have fired it 18 times (I think) and have no
problem getting it up to temp, however, it does take inordinately long to
get to temp (the 10 firings to cone 10 have taken 14-19 hours, bisque temp
takes 12+). I thought I'd try a higher stack, eventually, to see if that
might speed things up a bit, but wasn't sure if that would help in this
case. Have to get a welder out to put some supports on the chimney first
because winds here tend to blow the brick down if I try just stacking it dry.
Do you think that it's worth a try? Or should I be putting in an
adjustable regulator?
Mishy, who isn't really all *that* upset with 14-19 hour firings, but
thinks it is a bit long for a 20 cu ft kiln
Michelle Lowe, potter in the Phoenix desert \|/ |
mishlowe@indirect.com -O- | |
mishlowe@aztec.asu.edu /|\ | | |
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http://www.amug.org/~mishlowe ____ |
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( )
<__>
DIANA PANCIOLI, ASSOC. PROF. on thu 9 apr 98
Dear Ellen:"
I used natural draught burners on two kilns, not at high altitude, but
sometimes with a good wind across the chimney to make trouble. I was
taught that the chimney had to be a certain distance above the roof peak
nearest. Because both my kilns were "inside" I did build chimneys that
were, if I remember correctly, at least 18 inches above the roof peak.
The chimneys and burners worked very well. I love the quiet of
inspirating burners. I left the damper open at the beginning of the fire
to get the chimney warm, then used the damper as one normally would to
control the atmosphere in the kiln.
Diana
EMU
On Wed, 8 Apr 1998, Marcia Selsor wrote:
> ----------------------------Original message----------------------------
> Dear Ellen,
> I hope we can get some responses from high altitude firers. I have been using
> natural draught burners for a long time. I am still convinced that one needs a
> strong draught for control. I fire gas with the damper 1/2-1/4 (reduction)
> open most of the time. The kilns are so controllable we have a mark on the
> damper shelf for beginners to follow
> when firing. To figure the natural draught as was mentioned on here several
> years ago, I brun paper in the chimney and when the ashes fly up, I think it
> is tall enough.
> What do others think? It would be helpful to hear about many different
> experiences with gas kilns. Where are the folks from Missoula or the Bray?
> Marcia in Montana
>
> Orion/Baker wrote:
> >
> > ----------------------------Original message----------------------------
> > I saw Marcia's piece today saying that she needed to raise the height of a
> > wood burning kiln's chimney in order to get it to draw at 6,000 ft. I
> > didn't doubt her for a minute when she said that flames shot out the top --
> > I'm sure that by speeding up the airflow, the entire combustion area got
> > quite a hustle -- the entire flame got stretched forward (upstream), and I
> > bet they really had to step up stoking speed to keep that dragon burning!
> > (I love a good fire, and I bet it was a hoot!)
> >
> > But "thin air" is "thin air," and even fast moving or compressed thin air
> > is still "thin" in terms of ratio of nitrogen:oxygen, etc. The higher you
> > go in the mountains, the harder it is to keep any flame burning efficiently
> > -- gas or wood. Beyond some altitudes, there may be no way that anyone can
> > get their kiln up to full temperature -- no matter how hard they blow on
> > the coals!
> >
> > What I was trying to share in the pieces I wrote about orifice sizing and
> > gas through-put (draught), was an approach to making gas firing at altitude
> > as efficient and controllable as possible, keeping as much heat in the kiln
> > chamber as long as you can (the place where it will do the most good).
> >
> > I wonder how high (altitude) anyone's regularly done wood firing -- and
> > how/if they could get to Cone 10, Cone 6, whatever...
> >
> > Best to all,
> >
> > Ellen Baker - Glacier, WA
> > orion@telcomplus.net
>
WardBurner on fri 10 apr 98
<thinks it is a bit long for a 20 cu ft kiln>>
Time is a function of the BTU's per cubic foot. More BTU's; a faster firing
(assuming you have a properly built kiln). Back when I had a 60 cubic foot
fiber car kiln, I fired it to cone 10 in 40 minutes one time, just to
see......You had to know fast dad's car would go didn't you?
Mishy, if you want to go faster you just need more powerful burners.
Marc Ward
Ward Burner Systems
PO Box 333
Dandridge, TN 37725
USA
423.397.2914 voice
423.397.1253 fax
wardburner@aol.com
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