mel jacobson on mon 22 oct 01
since hank changed my life as a potter, i have had
some burning questions:
1. when i fire down...i seem to get a wonderful
total firing...no losses. the strange part is that
i also am getting total kiln reduction. why would
firing down affect reduction?
2. when i fire, the back flu area that is always cool,
is no longer cool. the pots are well reduced and they
are all melted totally.
3. i realize that time has entered into this equation.
and i have other theories that i will not muddy this
question with. i would like others to respond to this.
it should make an interesting topic.
4. so, let us see what people have to say.
i am sure that this applies to electric kilns.
some basic settling problems could be solved
with just a little time at 1900.
mel
From:
Minnetonka, Minnesota, U.S.A.
web site: http://www.pclink.com/melpots
WHC228@AOL.COM on mon 22 oct 01
Mel
No one seems to talk about the length of the flame having anything to do with
the way a kiln fires. I suspect that during the time that you are firing down
that the flame is turned down and that makes it shorter. The tip of the flame
is the hottest part, and would move toward the bottom of the kiln and give a
different heat pattern.
I have routinely soaked my kilns at the mattering temperature and fired them
down for years. I makes the glazes look a lot nicer. I suspect that it gives
the glaze materials time to react with one another. I can't explain why your
pots look more reduced, but it could be that they were reduced and only
appeared not to be because they had not been at temperature long enough.
That is my guess.
Bill
Craig Martell on mon 22 oct 01
mel j axed:
>1. when i fire down...i seem to get a wonderful
>total firing...no losses. the strange part is that
>i also am getting total kiln reduction. why would
>firing down affect reduction?
Hello mel:
I'll throw out one possibility and then that can be thrown out by the rest
of the list. Know what I mean?
Many glazes don't "set", or become unreactive to atmosphere and other
stimuli until very low temperatures are reached. Downfiring will still
contribute positive results with extra heatwork and atmosphere.
see you when you get to Or. Craig Martell in the aforementioned state.
Hank Murrow on mon 22 oct 01
>since hank changed my life as a potter, i have had
>some burning questions:
>
>1. when i fire down...i seem to get a wonderful
>total firing...no losses. the strange part is that
>i also am getting total kiln reduction. why would
>firing down affect reduction?
****Cannot answer this question.
>2. when i fire, the back flu area that is always cool,
>is no longer cool. the pots are well reduced and they
>are all melted totally.
****Time, and perhaps the clean atmosphere during the soak mainly
affects this area.
>i am sure that this applies to electric kilns.
>some basic settling problems could be solved
>with just a little time at 1900.
>mel
****I have no experience at this temperature with electrics, but in
my doorless fiber kiln I fire about half my work @ C/10 in oxidation, and
find that the oxidizing soak during cooling can be used anywhere from 1800F
to 2100F to good effect. Pinholes disappear with a soak at the higher
temps, while color seems richer at the lower temps. Ditto for the C/10
reduction fires. I have not tried a soak which begins at 2100F and slowly
falls to 1800F over say, a six or eight hour period. Good experiment,
though.
Worrying about contributing to the delinquency of a Major, Hank in Eugene
Mark Mondloch on mon 22 oct 01
I had been having glaze problems in my propane MFT but seem to have gotten a
handle on my problems lately mostly with adjustments to my firing protocol.
One of the changes that I believe is making a big difference is that after I
shut the burners off, I open the damper and the top peep in the door. There
is enough draw from the chimney to suck into the peep at first. The draw
diminishes until about 1900 F when it seems to be equalize and no longer
sucks in.
I'm wondering if my improved results doing this is might be related to the
improved results of those who are firing down? My work is fairly large and
thick so this drop takes awhile even with the air drawing through - maybe 1
1/2 hours in my kiln so I don't think you'd really call this a crash cool.
But then maybe those who do crash cool are getting improved results from the
fresh atmosphere being introduced too?
I've heard it said that there is some reduction formed and/or sulfur release
going on during the initial stages of cool-down. Theory- perhaps that by
letting the top temp drop I am stopping any out-gassing from materials that
need that top temp to break down. But then by maintaining enough( but lower)
temp to keep the glaze melted and having a clean atmosphere moving through
the kiln, blemishes that had formed while still at peak temp have a chance
to heal over without any new ones being formed?
Sorry for the rambling nature of this but I've been pondering this stuff and
can't seem to wrap my mind around it. I appreciate the discussion.
out to check the kiln,
Sylvia
---
Mark & Sylvia Mondloch
Silver Creek Pottery & Forge
W6725 Hwy 144
Random Lake ,Wi 53075
HotArt@silvercreekpottery.com
http://www.silvercreekpottery.com
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