options in porcelain on tue 10 sep 02
I have a Bailey 18/12 natural gas kiln. I've finally
figured out how to reduce (sort of) but my pots are
oxidized on one side and reduced on the other. I know
this is caused by the lack of turbulence in the kiln
during reduction.
Through various articles I've read, I understand that
the gas needs to be mixed with air before entering the
kiln (this does not cause oxidation because you are
controlling reduction with the damper) so my last
firing I opened the air flaps on the blowers 1/2 inch
while reducing without increasing the fan speed.
The previous firing I kept them closed and had a
definite streaming problem. But opening the flaps
seemed to help but I was having trouble with the kiln
stalling.
So my question is: how do you close off the secondary
air (damper), get turbulence, and reduce all at the
same time while keeping the temperature firing to cone
9 1/2?
Ronda in Virginia
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KLeSueur@AOL.COM on tue 10 sep 02
<air (damper), get turbulence, and reduce all at the
same time while keeping the temperature firing to cone
9 1/2?>>
I would suggest you section off your blower openings into ten sections. Mark them: position #1, #2, etc. Do the same with your damper.
Then on your next firing record the positions of both. You are making too drastic of adjustments on your blowers. Closing them completely makes no sense. The gas needs air to combust. You should make small adjustments in each firing. Recording each and looking at the results until you get what you want. Every kiln fires differently. It's a learning process. But without records you are flying blind.
Compare it to baking. If you were baking a cake at 450 degrees and it didn't turn out, you wouldn't try the next time at 200 degrees (well maybe you would). You would lower the temperature each time by 25-50 degrees until you got the desired result.
There are lots of tools that can help. Pyrometers, co2 analyzers. But these are only tools. You'll have to learn it by doing it.
Kathi LeSueur
foxpots on wed 11 sep 02
Dear Ronda,
If you have a Bailey kiln you own Jim Bailey. They are experts on firing
their kilns (and loading them properly so they fire properly). I bought a
Bailey 48/31 last year. My husband fired it (and died last 9/12). I had to
learn to fire it. Called Bailey. Jim talked on the phone with me for a
week, making me stop firing it, change bricks around, start firing it again,
stop firing it, change stuff around; then the day I actually fired it, he
was on the phone with me ALL DAY LONG (that isn't yelling, it is in caps for
the sheer amazement of his contribution to my education). We kept up with
the temperature, minute by minute. I just can't tell you all that got
stuffed into my thick skull that day. Bottom line, call Bailey. They are
the experts on their kilns. I can't imagine that you would be sorry.
Good luck,
Jean Wadsworth Cochran
Fox Hollow Pottery
----- Original Message -----
From: "options in porcelain"
To:
Sent: Tuesday, September 10, 2002 4:26 PM
Subject: Gas Kiln & streaming
> I have a Bailey 18/12 natural gas kiln. I've finally
> figured out how to reduce (sort of) but my pots are
> oxidized on one side and reduced on the other. I know
> this is caused by the lack of turbulence in the kiln
> during reduction.
>
> Through various articles I've read, I understand that
> the gas needs to be mixed with air before entering the
> kiln (this does not cause oxidation because you are
> controlling reduction with the damper) so my last
> firing I opened the air flaps on the blowers 1/2 inch
> while reducing without increasing the fan speed.
>
> The previous firing I kept them closed and had a
> definite streaming problem. But opening the flaps
> seemed to help but I was having trouble with the kiln
> stalling.
>
> So my question is: how do you close off the secondary
> air (damper), get turbulence, and reduce all at the
> same time while keeping the temperature firing to cone
> 9 1/2?
>
> Ronda in Virginia
>
> __________________________________________________
> Yahoo! - We Remember
> 9-11: A tribute to the more than 3,000 lives lost
> http://dir.remember.yahoo.com/tribute
>
>
____________________________________________________________________________
__
> 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.
Liz Willoughby on thu 12 sep 02
Hello Ronda, Sorry to be late in replying to your question. Been
doing a lot of deleting lately, studio tour coming up.
I have a Bailey too, the next size up from yours. You should have a
manual that came with the kiln, if not, call Bailey's for one, and
yes talk to Jim, as Jean says. He helped me too, when I was having
trouble getting even reduction.
My flaps are open only 1/4 inch, with the fans on medium/high before
I go into reduction. To get a good reduction flame, you should CLOSE
your flaps, turn the fans on low, close the damper to around a 2 "
opening. It takes about an hour to get into good reduction, slinky
flame out the bottom peep, stronger one out the top peep, and a good
flame out the kiln through the "cage" above the damper. I then turn
the fans to medium and pull out the damper slightly. TINY
adjustments to the damper make a big difference. I leave the flaps
closed all the way to the end of the firing. I fire a lot of carbon
trap shinos, but also fire tenmokus and celadons. All thrive with
this method.
If the kiln starts stalling, I open the damper a little, and also
increase the gas. I try to keep the kiln climbing after going into
reduction to 40 degrees C. an hour.
Remember that there is a lot of secondary air coming in around the
burners. And also remember that just because the flaps are closed
does not mean that air is not getting in. The flaps are not really
snug against the fans.
If you would like, I will send you more about my firing to you privately.
Meticky Liz
>I have a Bailey 18/12 natural gas kiln. I've finally
>figured out how to reduce (sort of) but my pots are
>oxidized on one side and reduced on the other. I know
>this is caused by the lack of turbulence in the kiln
>during reduction.
>
>Through various articles I've read, I understand that
>the gas needs to be mixed with air before entering the
>kiln (this does not cause oxidation because you are
>controlling reduction with the damper) so my last
>firing I opened the air flaps on the blowers 1/2 inch
>while reducing without increasing the fan speed.
>
>The previous firing I kept them closed and had a
>definite streaming problem. But opening the flaps
>seemed to help but I was having trouble with the kiln
>stalling.
>
>So my question is: how do you close off the secondary
>air (damper), get turbulence, and reduce all at the
>same time while keeping the temperature firing to cone
>9 1/2?
>
>Ronda in Virginia
>
>__________________________________________________
>Yahoo! - We Remember
>9-11: A tribute to the more than 3,000 lives lost
>http://dir.remember.yahoo.com/tribute
>
>______________________________________________________________________________
>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.
Liz Willoughby
RR 1
2903 Shelter Valley Rd.
Grafton, On.
Canada
K0K 2G0
e-mail lizwill@phc.igs.net
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