Jack Evert on sun 10 jan 99
Greetings! I am new to Clayart. I have just converted an old electric kiln
into a gas kiln. I did this by drilling holes in the top and placing on my
Raku, soft brick Hearth and combustion chamber. I have 9 one inch holes in
the top. The opening into the chamber is 2 "h x 4"wide. I have fired a
couple of bisques and it works fine. But when I looked at my 04 cones, I
noticed the top one just bend and the bottom melted. The kiln is about 18"
deep x 20+" across. Anyway, I have decided to try a high fire cone 10. I am
using a small burner which came with my Zen Raku Kiln. I am assuming the
difference in temp will continue. I was wonder what I might to try to even it
out. I thought I might fill one of the holes. I did rearrange the combustion
chamber, moving the brick I place in front of the burner more to the center of
the chamber but still blocking the flame. Originally, when I noticed the
difference in temp, I had the brick in front of the flame but also up against
one side. As one looked down into the chamber it the brick came off the side
wall and in front of the burner. Now, looking down, there is space all around
the brick, which still remains in front of the burner. Three stilts are in
the chamber, rise about the floor of the kiln and are what I place the first
shelf on. The gap between the floor and the shelve is only about 1/4" I Hope
that is enough info. Any words, wisdom or warnings would be appreciated.
One more antidote. Went "shopping" today at the area Salvation Army and Good
Will stores for pottery stuff. Got a great gram scale for $4, an old sifter
(with arm which turns the hand and bar which cleans top and bottom of screen!
Kinda small, but only $4) I got a fireplace popcorn maker. I think I will
try to find some mess screen and make my own sieve. I just couldn't see
spending $20 plus for a screen/shifter. Bought some $3 coveralls, some misc.
tools or items for measuring, scoring and pouring! It was great fun.
Thanks for being there.
Jack Evert
Issaquah, WA
Formerly of Chicago, Minnesota, PA and studied at Luther College with Dean
Schwartz, '73, Helped move Jim Rowe of Rowe Pottery to Cambridge WI in 74 and
finally apprenticed with "The Minnesota Potter" Jasper Bond!)
jacpottery@aol.com
Thonas C. Curran on tue 12 jan 99
Jack Evert wrote about temperature difference between top and bottom of
electric kiln he converted to gas:
Jack, I have an small updraft Wrap portable gas kiln purchased maybe 20
years ago in order to do copper reds. It has always fired about cone 10
on bottom shelf, cone 6 or so at the top. I just use a variety of
glazes to compensate. When I was only doing small scale pottery,
everything was OK except for the fact I had little success with the
copper reds when compared with the time expended. After I started
playing down at Skidmore College and using their facilities for R and R
(is that rejuvenation and reduction kilns?), I got my Wrap out again for
raku, and then this year I tried the cone 10 firing with taller pieces.
One piece only about 8" high was fired to maturity at base and
underfired on top. Now I limit my at home studio reduction firing to
smaller pieces about 6" or less and things are fine...even though the
kiln still fires at cone 6 on top and 10 on bottom. I do limit copper
red experiments to fewer pieces per load and include less chancy glaze
trials and pots so there's always something in the load I can depend on
to keep discouragement away. ( I have also learned to place a kiln
shelf on top of the top shelf load except for when I raku...about an
inch or even a tad less between kiln lid and the shelf. That makes a
difference.) Perhaps other Clayarters will have better info, but I
share mine for what it's worth.
Carolyn aka CNC
Bert Stevens on tue 12 jan 99
try raising the bottm shelf a little and open the top up a little more,
more holes or bigger holes...use a piece of kiln shelf as damper....
>Date: Sun, 10 Jan 1999 08:17:05 EST
>Reply-To: Ceramic Arts Discussion List
>From: Jack Evert
>Subject: How Do I Even out the Firing?
>To: CLAYART@LSV.UKY.EDU
>
>----------------------------Original
message----------------------------
>Greetings! I am new to Clayart. I have just converted an old electric
kiln
>into a gas kiln. I did this by drilling holes in the top and placing
on my
>Raku, soft brick Hearth and combustion chamber. I have 9 one inch
holes in
>the top. The opening into the chamber is 2 "h x 4"wide. I have fired
a
>couple of bisques and it works fine. But when I looked at my 04 cones,
I
>noticed the top one just bend and the bottom melted. The kiln is
about 18"
>deep x 20+" across. Anyway, I have decided to try a high fire cone
10. I am
>using a small burner which came with my Zen Raku Kiln. I am assuming
the
>difference in temp will continue. I was wonder what I might to try to
even it
>out. I thought I might fill one of the holes. I did rearrange the
combustion
>chamber, moving the brick I place in front of the burner more to the
center of
>the chamber but still blocking the flame. Originally, when I noticed
the
>difference in temp, I had the brick in front of the flame but also up
against
>one side. As one looked down into the chamber it the brick came off
the side
>wall and in front of the burner. Now, looking down, there is space all
around
>the brick, which still remains in front of the burner. Three stilts
are in
>the chamber, rise about the floor of the kiln and are what I place the
first
>shelf on. The gap between the floor and the shelve is only about 1/4"
I Hope
>that is enough info. Any words, wisdom or warnings would be
appreciated.
>
>One more antidote. Went "shopping" today at the area Salvation Army
and Good
>Will stores for pottery stuff. Got a great gram scale for $4, an old
sifter
>(with arm which turns the hand and bar which cleans top and bottom of
screen!
>Kinda small, but only $4) I got a fireplace popcorn maker. I think I
will
>try to find some mess screen and make my own sieve. I just couldn't
see
>spending $20 plus for a screen/shifter. Bought some $3 coveralls, some
misc.
>tools or items for measuring, scoring and pouring! It was great fun.
>
>Thanks for being there.
>
>Jack Evert
>Issaquah, WA
>Formerly of Chicago, Minnesota, PA and studied at Luther College with
Dean
>Schwartz, '73, Helped move Jim Rowe of Rowe Pottery to Cambridge WI in
74 and
>finally apprenticed with "The Minnesota Potter" Jasper Bond!)
>jacpottery@aol.com
>
Bert Stevens
b_a_stevens@hotmail.com
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
Stephen Mills on tue 12 jan 99
Jack stop using the brick baffle. Instead angle the burner so that the
flame circulates clockwise around the Kiln, and set your wares on SQUARE
shelves whose corners miss the sides by 1/2 an inch to 1 inch. the fire
climbs up the Kiln in a flat spiral and is partially deflected into the
pots by the shelf corners. With the baffle brick system the heat is held
down and then heads for the skies, missing your pots in the process. The
system I've described above works for me, from cone 06 to cone 10. I do
Raku and Stoneware in the same Kiln
Steve
Bath
UK
In message , Jack Evert writes
>----------------------------Original message----------------------------
>Greetings! I am new to Clayart. I have just converted an old electric kiln
>into a gas kiln. I did this by drilling holes in the top and placing on my
>Raku, soft brick Hearth and combustion chamber. I have 9 one inch holes in
>the top. The opening into the chamber is 2 "h x 4"wide. I have fired a
>couple of bisques and it works fine. But when I looked at my 04 cones, I
>noticed the top one just bend and the bottom melted. The kiln is about 18"
>deep x 20+" across. Anyway, I have decided to try a high fire cone 10. I am
>using a small burner which came with my Zen Raku Kiln. I am assuming the
>difference in temp will continue. I was wonder what I might to try to even it
>out. I thought I might fill one of the holes. I did rearrange the combustion
>chamber, moving the brick I place in front of the burner more to the center of
>the chamber but still blocking the flame. Originally, when I noticed the
>difference in temp, I had the brick in front of the flame but also up against
>one side. As one looked down into the chamber it the brick came off the side
>wall and in front of the burner. Now, looking down, there is space all around
>the brick, which still remains in front of the burner. Three stilts are in
>the chamber, rise about the floor of the kiln and are what I place the first
>shelf on. The gap between the floor and the shelve is only about 1/4" I Hope
>that is enough info. Any words, wisdom or warnings would be appreciated.
>
>One more antidote. Went "shopping" today at the area Salvation Army and Good
>Will stores for pottery stuff. Got a great gram scale for $4, an old sifter
>(with arm which turns the hand and bar which cleans top and bottom of screen!
>Kinda small, but only $4) I got a fireplace popcorn maker. I think I will
>try to find some mess screen and make my own sieve. I just couldn't see
>spending $20 plus for a screen/shifter. Bought some $3 coveralls, some misc.
>tools or items for measuring, scoring and pouring! It was great fun.
>
>Thanks for being there.
>
>Jack Evert
>Issaquah, WA
>Formerly of Chicago, Minnesota, PA and studied at Luther College with Dean
>Schwartz, '73, Helped move Jim Rowe of Rowe Pottery to Cambridge WI in 74 and
>finally apprenticed with "The Minnesota Potter" Jasper Bond!)
>jacpottery@aol.com
>
--
Steve Mills
Bath
UK
home e-mail: stevemills@mudslinger.demon.co.uk
work e-mail: stevemills@bathpotters.demon.co.uk
own website: http://www.mudslinger.demon.co.uk
BPS website: http://www.bathpotters.demon.co.uk
Thonas C. Curran on wed 13 jan 99
Dear Steve, Thanks so much for the posting on evening out the temp. on
the gas kiln
firings! My response to Jack's question was less helpful because it
told him to use diff. glazes for top and bottom. I can hardly wait for
temperatures around here to moderate so I can try your suggestions in my
portable kiln! Cheers from Carolyn aka CNC
orion on wed 13 jan 99
I agree with Steve (in Bath) regarding flame direction/deflection -- great
circulation is essential!
But you may also want to consider how evenly your ware (including shelves!)
is distributed, from top to bottom; also from shelf-edge inward. When the
kiln is first heating, densely packed areas tend to act as a "heat sink" --
taking longer to come up to temperature than sparely loaded areas. Later
in the firing, these dense areas may actually become radiant "hot spots"
compared to the less densely packed ones.
So much to consider, always! Good firings to all :))
Ellen Baker -- Glacier, WA
orion@telcomplus.net
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