Paul on fri 27 dec 02
Hello,
i am intersted in hearing how some people even out there firings. My kiln
has two burners coming in the back with two right- angle bricks positioned
vertically on each side as the only bagwall. They are about two-thirds the
length of the flame trench away from the burners (close to the front wall of
kiln) and i am finding that the front of the kiln is up to two full cones
hotter than the back, especially on the bottom. The kiln is also coated with
ITC and the cones drop very fast, though often do not look overfired, even
with ^11 down flat.
Anyway, i have moved the target bricks forward and back, with varying
results but always a considerable cone differential between front and back.
I stack the kiln accordingly, but can not help but wonder if some potters
out there have figured this out allready, basically how to "balance" this
type of kiln.
One things i can add is that i cut the exit flue down in half; it was over
81 square inches and causing dead spots close to it, so that helped a lot.
It also made it a lot easier to get an even reduction.
So if anyone has had this experience and can offer and suggestions, i would
be most thankful to hear. Thanks.
Paul B
Paul on thu 29 jul 04
Hello,
I posted this before and got a lot of good advice which did help, but
still I have an issue where the front-middle gets to temp long before
the whole top section. In most cases I can stack around this because
some glazes need to go hotter than others, but there still always seems
to be a few pieces that got a little to hot, and a few others that
needed more heat and in some cases have to be re-fired. Mainly I am
wondering, for those with kilns that fire "dead even", how do you do it?
I have two burners coming in from the back on a downdraft 70 cu.ft car
kiln. I was advised to work with the damper by being careful not to keep
it open too much, as it can pull heat down from the top of the kiln too
much. I did try this but I generally have a heavy reduction for most of
the firing (from cone 012 - cone 9) so the damper is almost never more
than 1/3 open anyway, and I think this did help somewhat but does not
seem to be the main issue.
I have also been building up a bagwall, it is up to 4 courses now
(bricks laying on their sides) and again, some good results but not
completely solved yet.
As for target bricks, I have one about 12" tall in the flame trench to
try to direct the flames up, about halfway between the burners and the
front of the flame trench.
I also do not stack as high up as I was, so there is plenty of space up
top.
So I am just trying to gather a little more info on this to see if I can
get it to even out a bit more. Mainly it is just because sometimes I
have pots that need to be fired and can not always be put in the ideal
part of the kiln, and I would like to eliminate the risk of overfiring
or underfiring.=20
If anyone else has anything to add I would be most thankful to hear.
Thanks!
Paul B
Falmouth, KY
Ben Shelton on mon 2 aug 04
Paul,
What are the dimensions of your kiln?
What kind of burners?
Man, The front middle is usually the coolest part of most kilns, especially
those with lose stack doors.
My first thought is that your flames need to be directed up more so than
they are now.
Ben
>I posted this before and got a lot of good advice which did help, but
>still I have an issue where the front-middle gets to temp long before
>the whole top section. In most cases I can stack around this because
>some glazes need to go hotter than others, but there still always seems
>to be a few pieces that got a little to hot, and a few others that
>needed more heat and in some cases have to be re-fired. Mainly I am
>wondering, for those with kilns that fire "dead even", how do you do it?
>
>I have two burners coming in from the back on a downdraft 70 cu.ft car
>kiln. I was advised to work with the damper by being careful not to keep
>it open too much, as it can pull heat down from the top of the kiln too
>much. I did try this but I generally have a heavy reduction for most of
>the firing (from cone 012 - cone 9) so the damper is almost never more
>than 1/3 open anyway, and I think this did help somewhat but does not
>seem to be the main issue.
>
>I have also been building up a bagwall, it is up to 4 courses now
>(bricks laying on their sides) and again, some good results but not
>completely solved yet.
>
>As for target bricks, I have one about 12" tall in the flame trench to
>try to direct the flames up, about halfway between the burners and the
>front of the flame trench.
>
>I also do not stack as high up as I was, so there is plenty of space up
>top.
>
>So I am just trying to gather a little more info on this to see if I can
>get it to even out a bit more. Mainly it is just because sometimes I
>have pots that need to be fired and can not always be put in the ideal
>part of the kiln, and I would like to eliminate the risk of overfiring
>or underfiring.
>
>If anyone else has anything to add I would be most thankful to hear.
>Thanks!
>
>Paul B
>
>Falmouth, KY
>
>___________________________________________________________________________
___
>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.
June Perry on tue 3 aug 04
If the damper setting doesn't correct it, then use the middle for tighter
stacking of plates and low pieces. That works for us in a kiln which has the same
problem.
In my old Geil kiln, the damper setting could cause that problem, so you
might want to fine tune that, once you get the top and bottom firing evening
through the bag wall adjustment.
Also, a nice slow firing with steady temperature rise often corrects a lot of
these nagging problems.
Regards,
June Perry
http://www.angelfire.com/art2/shambhalapottery/
| |
|
