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reduction and smoke ; was : several thoughts in a row

updated mon 29 may 06

 

Lee Love on sun 28 may 06


In clayart@yahoogroups.com, David Beumee wrote:

> Pete Pinnell taught a glaze class at Anderson Ranch in 1989, and his
> knowledge and understanding about reduction firing were a revelation.

I was fortunate to be able to do a glaze chemistry and firing
workshop with Pete about 13 years ago at Northern Clay Center. (An
aside: I have to add to the long list of people that
are"Minnesota/Wisconsin State Treasures" (I don't think any steal the
thunder of the others): I think Peter Leach did a lot to enhance the
clay culture in the region when he lead the effort to create the
Northern Clay Center. Many of the best potters, ceramic artists and
scholars from around the world were brought to the Twin Cities because
of that institution.

Back to Pete...

He is a glaze wizard and his firing with the carbon monoxide
sniffer (said his oxiprobe was too expensive to haul around), opened
the eyes of everyone who participated. He can tweak reduction by
putting a small piece of insulating blanket at the seam where the
damper enters the kiln.

The other thing I have realized since I started firing with wood
exclusively, is that our notions about reduction firing seemed to be all
based upon firing gas and oil kilns. Traditionally, you did not
have a constant atmosphere, but rather, one that cycles through
reduction, neutral, oxidation, on every stoke. I imagine that it would
be possible to copy this cycle with a gas or oil kiln, if you used a
computer to do the cycling, or had someone on the damper moving it every
5 minutes or so.

Because of this cycling, many of the glazes that depended upon
special reduction were fired in saggers. I visited the Idemitsu
Museum in Tokyo yesterday and the most exciting part of the collection
is the "shard room" full of pieces of pots from the Middle East,
China, Korea and Japan. It was really wonderful to be able to see
cross sections of many of the old pots. Pots from around the world
have been excavated from the Egyptian sites: Japan, China, Korea,
Rome, Greece.... I can't remember all the origins. Don't miss it if
you go to Tokyo.

Also, I saw celadons and shockingly blue Chuns in their
saggers. To protect these glazes from re-oxidation in a wood fuel
kiln, they were put in sealed saggers. Shinos were also fired this
way too. I also saw Hazan shards (founder of the muesum was a personal
friend of Hazan.) He used saggers for his tenmoku shapes. They had
an example on display, along with its sagger that was sealed shut with
some kind of sealing or mortar.

Smoke from a woodkiln can be controlled by lengthening the
chimney. I have a tall chimney and my kiln doesn't smoke a lot.
The longer chimney helps the carbon particles burn before they leave the
stack. I am guessing a brick chimney is better than a metal one,
because it holds the heat better. Maybe fiber lined metal isn't so
bad? Kusakabe speaks about his experiements with stack length and
smoke reduction in his woodfire book. Search his name at Amazon.com

--
Lee In Mashiko, Japan
http://mashiko.org
http://seisokuro.blogspot.com/