mel jacobson on fri 27 aug 99
smoke never means reduction.
it means that your flames are starved for oxygen.
i have seen kilns covered with soot, carbon everywhere.
and not a well reduced kiln ever.
a well reduced kiln should not be smoking at all.
you want the smoke, carbon inside the kiln, not outside.
a back pressure flame of about 5 inches from the spy ports is more
than enough.
no smoke should ever come from your stack...ever.
my neighbors of 38 years have never, never known when i fire.
they just do not notice.
you would have to line up the stack top with some trees to see the
heat waves coming out to know.
reduction is controlled by primary air, secondary air. flu and gas pressure.
put those in perfect combination...and bingo...good reduction.
mel.mn
http://www.pclink.com/melpots
from minnetonka, minnesota, u.s.a.
Cameron on sat 28 aug 99
To Mel Jacobson
Thank you , thank you, thank you. Finally someone who gets it!
You do not need smoke to have good reduction, in fact smoke
doesn't mean you have reduction evenly inside the kiln.
You can get very strong reduction with 0.5% CO and that does not
produce smoke. For years I have been telling folks to do it right
and forget the smoke, yet even at a famous, large university in
the same kiln room where the ceramic engineering department fires,
there is a kiln all blackened by smoke, totally unnecessary.
This data was worked out decades ago at Battelle Memorial
Institute to answer just this question about smoke and how much CO
is needed to get pottery reduced.
Cameron
--
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Stanley Irvin on sun 29 aug 99
Mel,
I just read your comments on getting good reduction. My experience with my
kiln is that if I don't get at least some small amount of smoke from my
chimney, then I don't get good reduction on the pots. My firing cycle is
about 16 hours long with about 9 hours of reduction. I live in an inner
city neighborhood and worry about neighbors seeing visible smoke from my
chimney. What you are saying makes sence but I'm wondering what, if
anything, you do with secondary air to create a reduction atmosphere other
than with the obvious damper adjustment. Also, do you have any suggestions
for what this situation points to in terms of my kiln design (flue, gas
pressure, secondary air, etc) that might be adjusted to improve the
reduction I am getting?
Many thanks,
Stan Irvin
Austin, Texas
David Hendley on sun 29 aug 99
| smoke never means reduction.
| it means that your flames are starved for oxygen.
Mel is speaking only about gas kilns, I presume, but
don't take that word 'never' as an absolute.
Smoke DOES mean reduction in a wood-fired kiln.
A wood-firer continually 'reads' the smoke and it's
a necessary part of a reduction firing.
When I first switched from gas to wood my first
firings were not properly reduced because I was still
going by the 'no-smoke' gas rules.
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: mel jacobson
To:
Sent: Friday, August 27, 1999 1:04 PM
Subject: reduction
| ----------------------------Original message----------------------------
| smoke never means reduction.
| it means that your flames are starved for oxygen.
|
| i have seen kilns covered with soot, carbon everywhere.
| and not a well reduced kiln ever.
|
| a well reduced kiln should not be smoking at all.
| you want the smoke, carbon inside the kiln, not outside.
|
| a back pressure flame of about 5 inches from the spy ports is more
| than enough.
|
| no smoke should ever come from your stack...ever.
| my neighbors of 38 years have never, never known when i fire.
| they just do not notice.
|
| you would have to line up the stack top with some trees to see the
| heat waves coming out to know.
|
| reduction is controlled by primary air, secondary air. flu and gas
pressure.
| put those in perfect combination...and bingo...good reduction.
| mel.mn
|
| http://www.pclink.com/melpots
| from minnetonka, minnesota, u.s.a.
|
Earl Brunner on sun 29 aug 99
I have a Geil Model 802 Fiber down draft kiln with about 8 c.f. of stacking
space. I have a harder time getting reduction in thebottom part of the kiln
than the top. I REALLY have to starve the kiln to get any backwash out of the
bottom plug at all. When I close the damper down that much then I have instant
and significant heat loss through out the kiln. This then slows down the whole
firing. It would interest me to see just how much an oxyprobe would help. I'm
not sure a new toy would be good for my marrage right now though.....
Stanley Irvin wrote:
> ----------------------------Original message----------------------------
> Mel,
> I just read your comments on getting good reduction. My experience with my
> kiln is that if I don't get at least some small amount of smoke from my
> chimney, then I don't get good reduction on the pots. My firing cycle is
> about 16 hours long with about 9 hours of reduction. I live in an inner
> city neighborhood and worry about neighbors seeing visible smoke from my
> chimney. What you are saying makes sence but I'm wondering what, if
> anything, you do with secondary air to create a reduction atmosphere other
> than with the obvious damper adjustment. Also, do you have any suggestions
> for what this situation points to in terms of my kiln design (flue, gas
> pressure, secondary air, etc) that might be adjusted to improve the
> reduction I am getting?
>
> Many thanks,
> Stan Irvin
> Austin, Texas
--
Earl Brunner
http://coyote.accessnv.com/bruec
mailto:bruec@anv.net
Robert Santerre on tue 31 aug 99
Hi Earl,
I have the same kiln. Also had the same problems, plus the top was always coole
than the bottom (by as much as 1-1.5 cones). I called Paul Geil and described t
problem. he suggested raising the burners . I now have the burners almost flus
with the outside metal skin of the bottom of the kiln. This has evened out the
kiln considerably (only 0.5 cone cooler at the top) and it made the reduction mo
even as well (like you. I still have to damp down the exit flue considerably to
enough back pressure to get the flame licking out of the bottom front peephole,
I don't have problems with temp. dropping). I have an oxyprobe placed in the ex
flue space just as it leaves the firing chamber. This is surely telling me what
the oxygen level is in the bottom of the kiln. I also watch to get about a 6-8"
flame out of the top of the flue (corresponds to about 0.6-0.65 on the oxy probe
Fiddling with all these indicators I manage to get pretty even firings and
reduction. Call Paul Geil, he's knowledgeable and helpful.
Good luck, Bob
////////////////////////////////////////////////////////////////////////////////
Earl Brunner wrote:
> ----------------------------Original message----------------------------
> I have a Geil Model 802 Fiber down draft kiln with about 8 c.f. of stacking
> space. I have a harder time getting reduction in thebottom part of the kiln
> than the top. I REALLY have to starve the kiln to get any backwash out of the
> bottom plug at all. When I close the damper down that much then I have instan
> and significant heat loss through out the kiln. This then slows down the whol
> firing. It would interest me to see just how much an oxyprobe would help. I'
> not sure a new toy would be good for my marrage right now though.....
>
> Stanley Irvin wrote:
>
> > ----------------------------Original message----------------------------
> > Mel,
> > I just read your comments on getting good reduction. My experience with my
> > kiln is that if I don't get at least some small amount of smoke from my
> > chimney, then I don't get good reduction on the pots. My firing cycle is
> > about 16 hours long with about 9 hours of reduction. I live in an inner
> > city neighborhood and worry about neighbors seeing visible smoke from my
> > chimney. What you are saying makes sence but I'm wondering what, if
> > anything, you do with secondary air to create a reduction atmosphere other
> > than with the obvious damper adjustment. Also, do you have any suggestions
> > for what this situation points to in terms of my kiln design (flue, gas
> > pressure, secondary air, etc) that might be adjusted to improve the
> > reduction I am getting?
> >
> > Many thanks,
> > Stan Irvin
> > Austin, Texas
>
> --
> Earl Brunner
> http://coyote.accessnv.com/bruec
> mailto:bruec@anv.net
Ray Aldridge on wed 1 sep 99
At 01:34 PM 8/29/99 EDT, you wrote:
>----------------------------Original message----------------------------
>| smoke never means reduction.
>| it means that your flames are starved for oxygen.
>
>Mel is speaking only about gas kilns, I presume, but
>don't take that word 'never' as an absolute.
>Smoke DOES mean reduction in a wood-fired kiln.
>A wood-firer continually 'reads' the smoke and it's
>a necessary part of a reduction firing.
>When I first switched from gas to wood my first
>firings were not properly reduced because I was still
>going by the 'no-smoke' gas rules.
>
This may also be true of oil-fired kilns. At any rate, I've had great
difficulty in getting even reduction without smoke in my small oil-fired
salt kiln. It could, I freely admit, just be that I don't know what I'm
doing.
Ray
Snail Scott on sat 18 may 02
At 08:35 AM 5/17/02 -0700, you wrote:
>...there was this old tale about potters got better reduction on
>overcast\rainy days. In a sense this is true but not really.
> When it is overcast there is more atmospheric pressure and less oxygen
>in the air.
This corresponds to my experience also. We didn't
call it 'better' reduction, though, but 'too damn
much reduction!'(Enough to prevent the kiln from
reaching temperature if the barometer dropped below
about 29.5.) Not enough secondary (or primary) air
in those old Alpine updrafts to cope with altitude,
I think. This notion is supported by the fact that
the kiln which was fitted with new burners (with wide
flame-retention tips which filled the burner ports)
was the worst offender. The kilns with the straight-
tube burners was nearly always able to reach
temperature regardless of the weather. The refitted
one wouldn't top ^7 on a stormy day, and couldn't
be pulled out of reduction above about ^2. Just not
enough 'air' in the atmosphere!
-Snail
Ivor and Olive Lewis on sat 11 aug 07
Dear Lee Love,
I recall that most bottled gases have a slight contamination with water. =
When I was in the Sintering Lab we had to dry our Hydrogen that was used =
to give us a highly reducing atmosphere.=20
You say would make body reduction more difficult. At cone 10plus, it reduces. >
Could you please explain this statement. It seems to be an unusual sort =
of Chemistry.
As I understand things, if Water reacts with Oxygen the result is =
Hydrogen Peroxide But if water is reduced you will be left with =
Hydrogen. Is this really what you mean ? Perhaps you could let me have =
a copy of that article.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
. =20
Lee Love on sat 11 aug 07
On 8/11/07, Ivor and Olive Lewis wrote:
> Could you please explain this statement. It seems to be an unusual sort of Chemistry.
Hi Ivor, it is in the article I have shared with you previously
from ceramics techincal.
--
Lee in Minneapolis, Minnesota USA
discussion on Beauty:
http://journals.fotki.com/togeika/beauty/
http://mashikopots.blogspot.com/
"Let the beauty we love be what we do." - Rumi
Dale Neese on fri 9 nov 07
Earlier when I began firing my kiln, Olsen 24 updraft, I found out that to
get the bottom clay reduced I needed to have all the burners at full turn up
pressure at red heat before beginning reduction at cone 09. I was following
the firing schedule that was provided and followed it to the letter but some
pots in areas near and around the bottom lacked the color. I contributed
that to too much secondary air coming in around the burners at cone 09
before my last couple of propane pressure turn ups on the remaining burners.
My kiln has 10 burners. I believed that those pots suffered from not being
evenly hot as other pots in the stack. I had no problem before reaching
reduction temperature of 09 even though I had a couple increases left on two
of the remaining burners underneath the stack. Now at beginning of red heat,
before reduction, all 10 of my burners are operating at final recommended
pressures. The kiln is cooking! This has helped take away the cold spots or
uneven areas of reduction in the bottom of the kiln stack. Then when I ease
the damper in at reduction the 2-4 inch flame at the bottom peep is stronger
but not so strong that there are copious amounts of smokey carbon coming
with it. But you can smell reduction and see carbon on the peep plugs
I leave the kiln to climb and don't make any adjustments until cone 7 tips
in the bottom, I pull the damper slightly to allow heat to rise. When cone 9
is down in the bottom I alternate with the damper open in oxidation
atmosphere for 5 minutes at a time, clearing the atmosphere to see the
remaining cones. Back to reduction until 10 is down in the bottom. Plug the
bottom peep cause there is nothing more you can do there. Concentrate on
watching when cone 10 goes flat in the top about 10 minutes later. Back all
the burners down to the same 1 inch of pressure, ease the damper in, not
enough to cause reduction, and let it soak for 5 minutes tops. Every part of
the kiln seems to radiate this almost white hot heat. Turn the main valve
off to the gas and close the kiln up. Done
Dale Tex
"across the alley from the Alamo"
San Antonio, Texas USA
http://ezproxy.stedwards.edu/hum/art/student/index.html
Scroll down to next exhibition
jonathan byler on mon 11 jul 11
nils,
where is a good place to locate the probe on an oxyprobe for an
initial attempt? I have bailey shuttle pro kilns with the burners
coming in from the rear at the bottom of the kiln. I was thinking
about the middle of the door somewhere? or maybe near where the
thermocouple is located midway up the back wall. or is it possible to
locate it in the flue below the damper? I figure if there is
reduction in the kiln, there ought to be in the flue also.
thanks,
jon byler
auburn university, AL
On Jul 11, 2011, at 10:32 AM, Nils Lou wrote:
> Robin, your account of firing ox-blood is a perfect example of over
> reduction producing a muddy color. Read Mel's posts on that history.
> For example, you stated that if a little reduction is good, more is
> better.
>
> Nope
>
> .83 on the o-probe is way too rich and wasteful of fuel. Try .55 to .
> 65 on
> the next batch and see the difference. It will surprise you and you
> will
> use much less fuel.
>
> As for fixing the first batch, try firing one piece to C6 in an
> electric, ie.,
> neutral atmosphere. Might help. Let us all know what happens. --nils
Nils Lou on mon 11 jul 11
Robin, your account of firing ox-blood is a perfect example of over
reduction producing a muddy color. Read Mel's posts on that history.
For example, you stated that if a little reduction is good, more is better.
Nope
.83 on the o-probe is way too rich and wasteful of fuel. Try .55 to .65 on
the next batch and see the difference. It will surprise you and you will
use much less fuel.
As for fixing the first batch, try firing one piece to C6 in an electric, i=
=3D
e.,
neutral atmosphere. Might help. Let us all know what happens. --nils
John Britt on wed 13 jul 11
Bailey sells oxiprobes:
http://www.baileypottery.com/kilns/oxyanalyzer.htm
johnbrittpottery.com
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