Peter Atwood on wed 12 jul 00
Ronda,
Although I am by no means an expert, some things that I have tried in the
past when trying to get to know a new kiln might be helpful to you. It seems
that every kiln is different and so may require various adjustments to what
you have learned from other firings in other kilns. The Baileys have an
excellent reputation and are supposed to be very even firing kilns according
to one local woman that I spoke with.
The first thing I would do is accept that the first couple of firings will
be rocky, but it sounds like you already have anticipated mixed results.
The second thing I would do is to make up several test batches of glazes
that are especially sensitive to reduction. I don't know what kind of glazes
you like and how heavy of a reduction that you desire. For the sake of
argument, a copper red or celadon will give you a pretty absolute indication
of reduction or oxidation. I have often fired those type of glazes and had
one side of the pot show strong reduction while the other was completely
oxidized. Same thing from shelf to shelf. Those pots gave me clues that
maybe my pots were too close together or my shelves were stacked in such a
way that circulation was inhibited.
Look closely at the pots you just fired. Are they definitely devoid of
reduction? If your body reduction happened at 010 for 30 minutes then you
should have seen some evidence. You could try lengthening the reduction to
60 or even 90 minutes.
It sounds like you use porcelain. Are you certain there is no reduction
occurring on it? I have noticed that sometimes reduced porcelain just looks
grey but sometimes that grey is subtle.
Maybe the glazes that you used and expected to see reduction in were ones
that worked better with an iron bearing body. Some glazes that I use such as
some rutile glazes need that fluxing from extra iron in the body to achieve
the desired results.
I'm shooting in the dark here but there are some things to chew on.
When we got our new Olympic Downdraft 9 we were convinced that it was a
piece of junk. We tested it numerous times and finally began to see some
even firings and then some really great results. I'm not sure that a
borrowed schedule from someone with the same kiln could have done it for us.
We needed to figure it out for ourselves. Of course, we are in a co-op
situation so the damage control was spread out amongst 10 people so no one
was losing a whole kiln load. Perhaps you are a production person with much
to lose.
Finally, call Bailey and see if they have support people to give you a
general guideline. I wish you the best!
Peter Atwood
Date: Tue, 11 Jul 2000 05:34:43 -0700
From: options in porcelain
Subject: Reduction firing
I just finished my first reduction firing in my Bailey
18/12 downdraft natural gas kiln and while nothing
melted to the kiln shelves I obviously missed getting
reduction. I did a 30 minute body reduction at ^010
(yellow flame, 5" backpressure from top spy port) then
another 45 minute one at ^9 bending to ^9 down. I do
not have an oxyprobe so I am trying to wing it based
on damper settings and flame color. Gas pressure is
not a problem.
Does anyone have a schedule they follow for reduction
firing this particular model of kiln? Do I need to do
reduction longer?
I fired a larger model of the Bailey kiln at school
and we had worked out a schedule that gave great
reduction. So I am at a loss as to where I went wrong.
I would also like to know the relationship between the
gas and blower fans. What setting does the fan need to
be on during firing? I started on low with the pilots
and eased up to med-low for the entire firing. Seemed
like if I turned them up on high the temp went down.
Ronda
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