Sharon Wetherby on mon 6 jun 11
June,
My firing buddy and I also fire with the primary air controllers wide open
from the start and through the finish. It has been a long learning process=
!
What used to take 13 or more hours to fire our downdraft kiln to cone 10,
now takes less than 8 hours. We had a lot of help and moral support from
Nils Lou via several e-mail messages and his book The Art of Firing. Here'=
s
a condensed description of how we fire now. We start firing with the
pressure gauges set on 3, air controllers wide open, and the dampers open.
We get a nice blue flame and no smell of gas. We watch our Oxyprobes like =
a
hawk once the kiln is hot enough that they start registering. We start
backing off the gas when the atmosphere gets too heavy and/or we smell gas.
Then if the atmosphere drops too low, we ease in the dampers by about a
pencil width. Our little kiln stalls if we set the gas too high or close
the dampers too much. When both top/bottom cone 10s are down, we shut off
the gas and leave the kiln open for about 10 minutes before closing the
dampers/spy openings (per Nils book). When the temperature drops to 1900
degrees F, we open the dampers a little and relight the gas (soft fluffy
flame) for about 15 minutes. Then we shut down and pack the openings. We
get nicely reduced pieces all through the kiln. This procedure works for
us, but every kiln is different. Here's a link to a picture of our kiln
http://lmrapotterystudio.com/pages/glazenfire.html Scroll down about
halfway from the top of the page.
Cheers,
Sharon Wetherby
Fort Worth, TX
>>>>>>>
Date: Sun, 5 Jun 2011 11:16:34 +0100
From: Steve Mills
original.mudslinger@GMAIL.COM
Subject: Re: Could use some help with backburning on Olympic gas kiln
burners
Dear June ,
I assume by shutters you mean the rotating air controls on the burners. I
fired a 7 cube version for a while, and found that wide open was the most
effective option, controlling atmosphere at the flue opening with two piece=
s
of kiln shelf to make a variable slot. If I shut the air down in any way I
was fighting my way up through a continuous reduction which in no way helpe=
d
gas economy.
My two-penny-worth.
Steve Mills
Bath UK
June on mon 6 jun 11
Thanks Sharon,
I didn't have any stall problems with the kiln - just the back burning from=
the minute the kiln was lit. The backburning continued no matter what the =
shutter setting and it only happened with one burner - the one next to the =
pilot burner.
Since the backburning was present no matter what the settings, I settled on=
the shutters about 3/8" for the whole firing, with damper fully open until=
I started reduction around cone 08. I had no problem with temperature clim=
b. If anything, at the beginning the kiln wanted to go too fast!
Warm regards,
June
http://wwww.shambhalapottery.blogspot.com
http://groups.yahoo.com/group/sodasaltfiring/
http://www.shambhalapottery.com
----- Original Message -----
From: Sharon Wetherby
To: Clayart@LSV.CERAMICS.ORG
Sent: Mon, 06 Jun 2011 16:09:24 -0000 (UTC)
Subject: Re: Backburning on Olympic Gas Kiln Burners
June,
My firing buddy and I also fire with the primary air controllers wide open
from the start and through the finish. It has been a long learning process=
!
What used to take 13 or more hours to fire our downdraft kiln to cone 10,
now takes less than 8 hours. We had a lot of help and moral support from
Nils Lou via several e-mail messages and his book The Art of Firing. Here'=
s
a condensed description of how we fire now. We start firing with the
pressure gauges set on 3, air controllers wide open, and the dampers open.
We get a nice blue flame and no smell of gas. We watch our Oxyprobes like =
a
hawk once the kiln is hot enough that they start registering. We start
backing off the gas when the atmosphere gets too heavy and/or we smell gas.
Then if the atmosphere drops too low, we ease in the dampers by about a
pencil width. Our little kiln stalls if we set the gas too high or close
the dampers too much. When both top/bottom cone 10s are down, we shut off
the gas and leave the kiln open for about 10 minutes before closing the
dampers/spy openings (per Nils book). When the temperature drops to 1900
degrees F, we open the dampers a little and relight the gas (soft fluffy
flame) for about 15 minutes. Then we shut down and pack the openings. We
get nicely reduced pieces all through the kiln. This procedure works for
us, but every kiln is different. Here's a link to a picture of our kiln
http://lmrapotterystudio.com/pages/glazenfire.html Scroll down about
halfway from the top of the page.
Cheers,
Sharon Wetherby
Fort Worth, TX
>>>>>>>
Date: Sun, 5 Jun 2011 11:16:34 +0100
From: Steve Mills
original.mudslinger@GMAIL.COM
Subject: Re: Could use some help with backburning on Olympic gas kiln
burners
Dear June ,
I assume by shutters you mean the rotating air controls on the burners. I
fired a 7 cube version for a while, and found that wide open was the most
effective option, controlling atmosphere at the flue opening with two piece=
s
of kiln shelf to make a variable slot. If I shut the air down in any way I
was fighting my way up through a continuous reduction which in no way helpe=
d
gas economy.
My two-penny-worth.
Steve Mills
Bath UK
douglas fur on mon 6 jun 11
June
" The backburning continued no matter what the shutter setting and it only
happened with one burner - the one next to the pilot burner."
I think you're on to it here- the pilot could be stealing gas capacity from
that burner. Back burning is when the flame burns back down the colum of
gasses faster than those gasses are moving out of the burner tube. At star=
t
up, with low draft, most of the energy of those gasses is from the gas jet
leaving the orifice. So there's a possibility the pilot is taking enough ga=
s
away from that burner to impact the velocity of gasses in the burner tube.
A constriction near the end of the burner tube forces the gasses to hurry u=
p
to get through the smaller hole. Screen could do this but I'd wonder about
zinc galvanizing burning off.... A flame retention tip, or a sponge brick
"cork" with a hole 3/4 the size of the tube diameter could do the same.
DRB
Seola Creek
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