Re: A Wood Firing Question, Charcoal Introduction
Lee
chamber, pine charcoal is introduced, covering the pots with charcoal.
The pots are set on clay pads that have shells on them. The floor
is covered with wet rice hull ash before the pots are set in. When
Shimaoka was alive, he placed all the pots in this chamber.
Sometimes there was charcoal found, unburnt in pots. The
charcoal did not deposit ash on the pots. It only created heavy
reduction. So unlike the pots in the firemouth, there was little
evidence of ash deposits on the pots, if any. The firemouth pots had
rivulets of ash on them. The Yohen chamber pots had no ash runs and
looked dull when you took them out of the kiln. They are polished,
some for a day or two, the results being a velvety/mat texture of
depth. The clay was a white shigaraki clay with feldpar stones in
it.
See Yohen chamber here:
http://claycraft.blogspot.com/2011/06/shimaokas-yohen-chamber.html
Shimaoka Yohen Pot:
http://p2.la-img.com/454/18073/6121163_1_m.jpg
These are pots of mine fired in the firebox of my wood kiln. They
were buried in a bed of coals:
http://mashikopots.blogspot.com/2007/06/firebox-tea-bowls.html
--
Lee Love in Minneapolis
http://mingeisota.blogspot.com/
"Ta tIr na n-óg ar chul an tI—tIr dlainn trina chéile"—that is, "The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
David McDonald
Shimaoka Sensei looking into the Yohen chamber, judging if it's ready for charcoal introduction;
Neon-Cat
Thanks!
Nice photos, David! The first photo is glorious!
I like to think of our reduction processes as merely the oxidation of carbon monoxide (CO). It is interesting to think about from this kind of reverse perspective -- the pots with their oxides and things and the potters adding to the entire firing experience and not just being acted upon or submitting to a final fate. This opens thought to the possibilities of both high and low temperature oxidation of CO.
Hopcalite, for use in gas masks, was developed around 1920 by A. B. Lamb, W. C. Bray, J. C. W. Frazer (Jour. Chem. Ind. Eng., 12, 213, 1920). It oxidizes carbon monoxide while being used. Here is its formula:
MnO2 – 50%
CuO (from carbonate) – 30
Co2O3 – 15
Ag2O – 5
During use, the contact area between the CO gas and the Mn-Cu-Co-Ag composite becomes hot, reaching red heat, about 1112 F/600 C. This heat burst will also be occuring on and in your pots and glazes when they are oxidizing carbon monoxide.
Marian
Neon-Cat Ceramics
> From: Lee <cwidde...@gmail.com>
> Subject: *ClayCraft* Re: A Wood Firing Question, Charcoal Introduction
<snip> The Yohen chamber pots had no ash runs and looked dull when you took them out of the kiln. They are polished, some for a day or two, the results being a velvety/mat texture of depth. The clay was a white shigaraki clay with feldpar stones in it. <snip>
Lee
--
Lee 李 Love in Minneapolis
Lee
> Lee, how did they polish the pots, as in with what?
> Thanks!
Traditionally, they polished with rice straw. But when I was there,
they used red and green 3M scrubbies. When I told the Shokunin they
were from my home State, I think they thought I was pulling their
legs.
The process usually went like this: First, the retired
Foreman would use a chisel and wet stone on the bottom. Then the
Foreman would use emery cloth on the body of the pot. Next, Kei,
Shimaoka's Grandson, would get the pot and use a dental drill on
anything that required it. Then, one of the other apprentices would
first use a red 3M pad, and then a green 3M pad on the pot. When the
pot was polished enough with the pads, then it was rubbed with a
cotton cloth. The pots would get oil from your hands at this stage.
It was boring work. In the summer, you'd often find your head
jerking awake. And you would freak about dropping a $5,000 to $25,000
pot on the ground. I always tried to sit on one of the car bench
seats with a dirt and not concrete floor underfoot.
What was dull brown and ruff, became satin mat with many colors and depth.
--
Lee 李 Love in Minneapolis
gary navarre
If that's what you can end up having to do to some pots out of a wood kiln then I'm not to far off in how I've been dealing with some of the "rougher" looking pieces. So far I used a chunk of kiln shelf for the basic cleaning of sharps on the foot, haven't had to chisel or grind much yet, but some of the fine ash/sand texture that didn't melt had me stumped thinking they were scrap until I tried emery papers down to 800 grit with some softening of the feel and some interesting effects like a piece of glass washed along the beach. When the surface gets wet a whole 'norther thing happens. I guess the Japanese have names for some of the effects I found in this kiln but I thought they would be scrap because to me they are flawed. Even some stress cracks filled with ash deposits are still acceptable if they look cool. I sure wish there were more folks nearby who knew about wood firing so we could do a load together and see what comes of a fairly long well
maintained fire. I've started collecting standing dead Tamarack, Spruce, Maple, Ironwood, and whatever else burns hotter than Balsam between 1" & 6" by 36" long for another firing. I should probably just get 500 lbs. of a wood fire stoneware and some extra fire clay and remake all those plaster popped and heat stress broken pots while I'm at it. We'll see after the show Sunday if I still have any enthusiasm or cash left for this fascinating hobby. I wouldn't be doing it if it weren't for Mom telling me to give it one more try.
Gary Navarre
Navarre Pottery
Navarre Enterprises
Norway, Michigan, USA
http://www.NavarrePottery.etsy.com
http://www.youtube.com/GindaUP
http://public.fotki.com/GindaUP/
--- On Sat, 7/16/11, Lee <tog...@gmail.com> wrote:
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Eric Suchman
Eric Suchman
"Seldom turns out the way it does in the song" -RH