Hank Murrow on fri 11 jan 02
>I am having problems evening out the temperature in my kiln. It is a gas
>kiln fueled by propane. The kiln has two forces air burners (MB500) in the
>back with a salt port above each burner. It is 54 Cubic Feet. The inside
>dimensions are 54 x 31.5 x 55. The kiln is hard brick with soft brick on
>the outside. I stack it two deep with shelves 12 x 24. I have tried to
>adjust the bagwall, open it up at bit, and adjust the stacking. The cold
>spots are on the bottom and the back. The shelves are 3" from the back 2
>1/2" in-between shelves and 2" in the front. This firing the bagwall has
>spaces in-between each brick with the spaces getting wider towards the back
>of the kiln, the bagwall is 3 bricks high on edge. This is the 6th or 7th
>time firing this kiln. I oxidize until 900 degrees C then reduce to 1000
>then neutral letting the kiln naturally reduce as it get to temp. Cone 10.
>I salt at 9 for 2 hours and then let the kiln oxidize for about 30 min,
>then I turn it off and open it up for 15 min then close it tight for the
>next day and open the following day. I am new at this and would love any
>input.
Dear Heather;
You did not mention whether there was a flue trough at the bottom
of the chamber, or if the flue exit is just at the back wall....even with
the floor. I wonder about the increased openings in the bag wall towards
the back of the kiln. I would have suggested increased openings towards the
front wall of the kiln. Gases speed up as they are forced to funnel through
tight openings, and this can cause a cooler temp in that region. That is
why with downdraft kilns it is a good idea to build in a flue trough under
the floor. It collects the gases under the floor and then shunts them out
the back wall.
You did not mention what kilnd of color you get with your firing
cycle. At Anderson Ranch back in the early 70s we found that a slow cool
would produce matter surfaces and very warm colors....browns and tans,
while a very quick cool would produce shiny surfaces and cold
colors...greys and grey-blues.
I hope we'll be able to help you sort this out in the course of a
few fires.
Cheers, Hank
Heather Bosworth on fri 11 jan 02
I am having problems evening out the temperature in my kiln. It is a gas
kiln fueled by propane. The kiln has two forces air burners (MB500) in the
back with a salt port above each burner. It is 54 Cubic Feet. The inside
dimensions are 54 x 31.5 x 55. The kiln is hard brick with soft brick on
the outside. I stack it two deep with shelves 12 x 24. I have tried to
adjust the bagwall, open it up at bit, and adjust the stacking. The cold
spots are on the bottom and the back. The shelves are 3" from the back 2
1/2" in-between shelves and 2" in the front. This firing the bagwall has
spaces in-between each brick with the spaces getting wider towards the back
of the kiln, the bagwall is 3 bricks high on edge. This is the 6th or 7th
time firing this kiln. I oxidize until 900 degrees C then reduce to 1000
then neutral letting the kiln naturally reduce as it get to temp. Cone 10.
I salt at 9 for 2 hours and then let the kiln oxidize for about 30 min,
then I turn it off and open it up for 15 min then close it tight for the
next day and open the following day. I am new at this and would love any
input.
Bosworth on sat 12 jan 02
Thank you for the suggestions. I do not have a flue trough (not much I can
do about that now), the part about the openings in the bag wall is
interesting. Figures my logic would be backwards. Does this mean that
opening the stack would also create a cool space?
Heather
----- Original Message -----
From: "Hank Murrow"
To:
Sent: Saturday, January 12, 2002 12:57 AM
Subject: Re: Kiln - even out temp.
> >I am having problems evening out the temperature in my kiln. It is a gas
> >kiln fueled by propane. The kiln has two forces air burners (MB500) in
the
> >back with a salt port above each burner. It is 54 Cubic Feet. The inside
> >dimensions are 54 x 31.5 x 55. The kiln is hard brick with soft brick on
> >the outside. I stack it two deep with shelves 12 x 24. I have tried to
> >adjust the bagwall, open it up at bit, and adjust the stacking. The cold
> >spots are on the bottom and the back. The shelves are 3" from the back 2
> >1/2" in-between shelves and 2" in the front. This firing the bagwall has
> >spaces in-between each brick with the spaces getting wider towards the
back
> >of the kiln, the bagwall is 3 bricks high on edge. This is the 6th or 7th
> >time firing this kiln. I oxidize until 900 degrees C then reduce to 1000
> >then neutral letting the kiln naturally reduce as it get to temp. Cone
10.
> >I salt at 9 for 2 hours and then let the kiln oxidize for about 30 min,
> >then I turn it off and open it up for 15 min then close it tight for the
> >next day and open the following day. I am new at this and would love any
> >input.
>
>
> Dear Heather;
>
> You did not mention whether there was a flue trough at the bottom
> of the chamber, or if the flue exit is just at the back wall....even with
> the floor. I wonder about the increased openings in the bag wall towards
> the back of the kiln. I would have suggested increased openings towards
the
> front wall of the kiln. Gases speed up as they are forced to funnel
through
> tight openings, and this can cause a cooler temp in that region. That is
> why with downdraft kilns it is a good idea to build in a flue trough under
> the floor. It collects the gases under the floor and then shunts them out
> the back wall.
>
> You did not mention what kilnd of color you get with your firing
> cycle. At Anderson Ranch back in the early 70s we found that a slow cool
> would produce matter surfaces and very warm colors....browns and tans,
> while a very quick cool would produce shiny surfaces and cold
> colors...greys and grey-blues.
>
> I hope we'll be able to help you sort this out in the course of a
> few fires.
>
> Cheers, Hank
>
>
____________________________________________________________________________
__
> 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.
Bosworth on sat 12 jan 02
I forgot to answer the question about color with the slow cooling. I am
getting glossy bright colors and warm tones. I do salt which helps with the
gloss. I heard that the quick cooling right after the kiln is turned off,
then the longer slow cooling at the bottom temp. does this? I'm not sure if
this is correct but it works for me.
Heather
> Thank you for the suggestions. I do not have a flue trough (not much I can
> do about that now), the part about the openings in the bag wall is
> interesting. Figures my logic would be backwards. Does this mean that
> opening the stack would also create a cool space?
>
> Heather
>
> ----- Original Message -----
> From: "Hank Murrow"
> To:
> Sent: Saturday, January 12, 2002 12:57 AM
> Subject: Re: Kiln - even out temp.
>
>
> > >I am having problems evening out the temperature in my kiln. It is a
gas
> > >kiln fueled by propane. The kiln has two forces air burners (MB500) in
> the
> > >back with a salt port above each burner. It is 54 Cubic Feet. The
inside
> > >dimensions are 54 x 31.5 x 55. The kiln is hard brick with soft brick
on
> > >the outside. I stack it two deep with shelves 12 x 24. I have tried to
> > >adjust the bagwall, open it up at bit, and adjust the stacking. The
cold
> > >spots are on the bottom and the back. The shelves are 3" from the back
2
> > >1/2" in-between shelves and 2" in the front. This firing the bagwall
has
> > >spaces in-between each brick with the spaces getting wider towards the
> back
> > >of the kiln, the bagwall is 3 bricks high on edge. This is the 6th or
7th
> > >time firing this kiln. I oxidize until 900 degrees C then reduce to
1000
> > >then neutral letting the kiln naturally reduce as it get to temp. Cone
> 10.
> > >I salt at 9 for 2 hours and then let the kiln oxidize for about 30 min,
> > >then I turn it off and open it up for 15 min then close it tight for
the
> > >next day and open the following day. I am new at this and would love
any
> > >input.
> >
> >
> > Dear Heather;
> >
> > You did not mention whether there was a flue trough at the
bottom
> > of the chamber, or if the flue exit is just at the back wall....even
with
> > the floor. I wonder about the increased openings in the bag wall towards
> > the back of the kiln. I would have suggested increased openings towards
> the
> > front wall of the kiln. Gases speed up as they are forced to funnel
> through
> > tight openings, and this can cause a cooler temp in that region. That is
> > why with downdraft kilns it is a good idea to build in a flue trough
under
> > the floor. It collects the gases under the floor and then shunts them
out
> > the back wall.
> >
> > You did not mention what kilnd of color you get with your firing
> > cycle. At Anderson Ranch back in the early 70s we found that a slow cool
> > would produce matter surfaces and very warm colors....browns and tans,
> > while a very quick cool would produce shiny surfaces and cold
> > colors...greys and grey-blues.
> >
> > I hope we'll be able to help you sort this out in the course of
a
> > few fires.
> >
> > Cheers, Hank
> >
> >
>
____________________________________________________________________________
> __
> > 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.
>
william schran on sat 12 jan 02
>You said - "The shelves are 3" from the back" - Try pushing the
>shelves closer to the back wall, maybe just an inch space.
Bill
>
>______________________________________________________________________________
>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.
Marvpots@AOL.COM on sun 13 jan 02
You also did not mention whether or not you are making adjustments with the
damper in order to even out heat distribution. With carefully observed
damper adjustments you should find a lick of flame comeing out of both the
top and bottom peep holes; if you are not geting this affect, change the
adjustment of the damper (i.e. degree of closing) until you do and see if
that does not help if not solve your problem.
Good luck!
Marvin Flowerman
marvpots@aol.com
| |
|
