David Hendley on mon 4 oct 99
Not being the scientific type like Gavin and Ivor, I
usually know what's happening by experience, but
couldn't explain why scientifically.
Anyway, I know that I like my kiln wood to be slightly wet.
I'm glad to be told what's happening in the combustion
chamber.
Ivor, would you tell us what methods people are using to
inject water into the airstream of their wood-fired kilns?
--
David Hendley
Maydelle, Texas
hendley@tyler.net
http://www.farmpots.com/
----- Original Message -----
From: I.Lewis
To:
Sent: Friday, October 01, 1999 2:12 PM
Subject: wet wood
----------------------------Original message----------------------------
------------------
Gavin Stairs seems to be having some trouble with those long words. Must say
I
was fascinated with "monotonically descending curve like an exponential".
Now I think I know what he means from the context of his posting but is the
word
he is looking for Asymptotically, meaning that it only approaches but never
reaches a steady value. The difference is so small that it is almost
unmeasurable.
I really do like Monotonically. In a poetic sense it is a fair description,
a
boring line. Almost as boring as the process of desiccation.
One notion which has not been mentioned, or so it would seem unless I have
missed something, is the additional calorific value of wet wood due to the
Water
Gas reaction. Above about 1100Celsius, superheated steam reacts freely with
carbon to give free hydrogen and carbon monoxide. So wet gas striking those
white hot coals in the fire box can give free combustible gas which promotes
increasing temperature as it burns with secondary air and the potential for
a
highly effective reducing atmosphere. I know that some people who fire with
wood
are now injecting water into the airstream. Given the potential high flame
temperature of burning hydrogen perhaps this style of firing should be
investigated further.
Always looking for things to torment my simple mind.
Ivor. In South Oz, where we now have a studio with a concrete floor which is
in
process of being sealed.
Hank Murrow on tue 12 oct 99
------------------
Dear Group=3B I've been following this discussion about the r=F4le of water
vapor in firing=3B and have a first thing to share with you. I got a
wonderful little booklet from Ohio State U. some years ago while I was
teaching at Ohio U.that clarified the role of water in firing ceramic
products. The name of this booklet is=3B=22Influence of Ambient Atmosphere =
in
Maturation of Structural Clay Products=22. Order Bulletin 204 from
Engineering Publications, 2070 Neil Avenue, Columbus, OH 43210. It was
=243.50 in 1969. Covers the introduction of water vapor in reduction and
oxidation fires=3B and contains some lovely color photos of the test series.
Perhaps a careful study of their publication list would reveal later
studies of the same questions. In any case it has helped me as a kiln
builder and potter enormously. I hope copies are still available=3B and that
it proves as useful to each of you. I am happily busy making pots just =
now=3B
but I have an extra copy which I am willing to send to anyone promising to
study it and report to the ClayArt list. Hank in Eugene
=3E----------------------------Original message----------------------------
Anyway, I know that I like my kiln wood to be slightly wet.
=3EI'm glad to be told what's happening in the combustion
=3Echamber.
=3E
=3EIvor, would you tell us what methods people are using to
=3Einject water into the airstream of their wood-fired kilns?
=3E
=3E--
=3EDavid Hendley
=3E---------------------------Original message----------------------------
=3EOne notion which has not been mentioned, or so it would seem unless I =
have
=3Emissed something, is the additional calorific value of wet wood due to =
the
=3EWater
=3EGas reaction. Above about 1100Celsius, superheated steam reacts freely =
with
=3Ecarbon to give free hydrogen and carbon monoxide. So wet gas striking =
those
=3Ewhite hot coals in the fire box can give free combustible gas which =
promotes
=3Eincreasing temperature as it burns with secondary air and the potential =
for
=3Ea
=3Ehighly effective reducing atmosphere. I know that some people who fire =
with
=3Ewood
=3Eare now injecting water into the airstream. Given the potential high =
flame
=3Etemperature of burning hydrogen perhaps this style of firing should be
=3Einvestigated further.
=3EIvor, In South Oz
Bill Campbell on wed 13 oct 99
Hank-Twenty years ago I visited PauL Chaleff At the Stissing Hollow Craft
Village near Pine Plains New York.He makes wood fired that he fires in an
anagama type kiln. He had some pots in his collection that he had brought
back from Japan . He had been over studying with a Japanese master.The pots
in question were black. He said [as I remember] thatwater was poured into the
upper stoke holes while the kiln was at temperature.to get that color.
I don`t know if he is still up there or not The last time I saw him was at
NCECA in Rochester and he said that he was spending part of his time in NYC.
I expect that he couldn`t be too hard to find .He would probably share that
info with you. Maybe someone on clayart would know where to find him.
Bill
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