Norman Aufrichtig on tue 30 may 06
i agree, but the first time i used an oxyprobe i was amazed a quarter of an
inch, with the damper, was the difference between oxidation and reduction,
what a learning tool, it gave me understanding, completely changed the way i
fired. spent about a thousand dollars for it at the time, was well worth it.
also bought a tool to measure the thickness of glaze from axner, had to
modify it, built a tripod around it, use it occasionally, good learning tool
but mostly do my glazing by eye and every other sense,it all gets more
complicated when one adds layering, each layer doing something else to the
whole, a wonderful adventure no end in sight.
norman
----- Original Message -----
From: "mel jacobson"
To:
Sent: Tuesday, May 30, 2006 6:53 AM
Subject: [CLAYART] reduction/glaze thickness
> please, those of you that are discussing
> reduction. (and keep at it, it is more than important.)
> all of my work in down firing reduction is about
> `observation`.
> i am not using chemistry calculations or theory.
>
> this is about seeing what happens when...
> you do this or that.
>
> also, i have found a great deal of smoke usually
> means you are wasting fuel. the smoke is unburned
> fuel. it is seeking oxygen outside the kiln.
>
> it is very much the same as in lee's fine post about
> glazing.
>
> old master potters know more about glaze thickness,
> spend more time fussing over it, than we can believe..
> but, the pots tell us they know what they are doing.
>
> years of observation, testing, understanding what is going
> on...instead of a gauge, he or she uses her mind and experience.
>
> if we depend on everything except our own experience and
> senses, we will often lose.
>
> it is like a recipe:
> it all depends.
> mel
> the first line in my story in `ceramics monthly` about
> the jian/iron saga pots....`i had to become an ancient
> chinese potter so i could understand what was going on.`
> i had to give up the oxyprobe, meters, kiln helpers.
> it was just me, the glaze, the clay and the fire.
> period.
>
> from: mel/minnetonka.mn.usa
> website: http://www.visi.com/~melpots/ (new website)
> http://my.pclink.com/~melpots3 old
>
> Clayart page link: http://www.visi.com/~melpots/clayart.html
>
>
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mel jacobson on tue 30 may 06
please, those of you that are discussing
reduction. (and keep at it, it is more than important.)
all of my work in down firing reduction is about
`observation`.
i am not using chemistry calculations or theory.
this is about seeing what happens when...
you do this or that.
also, i have found a great deal of smoke usually
means you are wasting fuel. the smoke is unburned
fuel. it is seeking oxygen outside the kiln.
it is very much the same as in lee's fine post about
glazing.
old master potters know more about glaze thickness,
spend more time fussing over it, than we can believe..
but, the pots tell us they know what they are doing.
years of observation, testing, understanding what is going
on...instead of a gauge, he or she uses her mind and experience.
if we depend on everything except our own experience and
senses, we will often lose.
it is like a recipe:
it all depends.
mel
the first line in my story in `ceramics monthly` about
the jian/iron saga pots....`i had to become an ancient
chinese potter so i could understand what was going on.`
i had to give up the oxyprobe, meters, kiln helpers.
it was just me, the glaze, the clay and the fire.
period.
from: mel/minnetonka.mn.usa
website: http://www.visi.com/~melpots/ (new website)
http://my.pclink.com/~melpots3 old
Clayart page link: http://www.visi.com/~melpots/clayart.html
Elizabeth Priddy on tue 30 may 06
Your need to give up the oxyprobe, the meters, and go
back to feel reminds me of the last raku lesson my
current apprentice had.
We were firing toward dusk and I said "OK, get ready
to go, it is about to hit time" and he said how do you
know?
I had just looked in the kiln and the glaze was molten
and beginning to "set", so I knew. He got out the
pyrometer (of course I have one) and checked and damn
if it wasn't time.
It is like Chris's last post of dropping tiles. I
taught her that a long time ago and she didn't believe
me when I told her we were going to make and fire
perfectly flat tiles in one full day. The next day,
when the kiln was opened (too hot but what the hell)
there was the proof.
And now she can pass ont he info and get to explain to
naysayers that it is true. Paul knows it is true, if
a little tricky. So does Steph. But there will still
be people declaring that it cannot work, that you must
use as much drywall as could insulate your studio.
People can be like that. It is amazing how someone
can be standing next to another who has perfect
confidence in what they are doing(which can only come
from repeated success) and tell them that it is not
going to work. It is incredibly insulting on the one
hand, and incredibly entertaining on the other.
I learned to guage kiln temperature by sight, by
color, because I never trusted the little cones that
went into the holders. And I saved one or two loads
from ruin by trusting my eyes to find a little bar
stuck on one of the holders and a sitter that would
have never tripped.
Pays to trust your senses. I also know if the oxygen
mix is right at a raku firing at 20 feet. It sounds
like a harrier jet when it is right.
E
Elizabeth Priddy
Beaufort, NC - USA
http://www.elizabethpriddy.com
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Tom at Hutchtel.net on tue 30 may 06
From: "mel jacobson"
Subject: reduction/glaze thickness
> it is very much the same as in lee's fine post about
> glazing.
>
> old master potters know more about glaze thickness,
> spend more time fussing over it, than we can believe..
> but, the pots tell us they know what they are doing.
>
> years of observation, testing, understanding what is going
> on...instead of a gauge, he or she uses her mind and experience.
>
> if we depend on everything except our own experience and
> senses, we will often lose.
>
The thickness issue is one, that like firing schedule, is never included in
the glaze recipe, yet is critical to success, When we try a new glaze, we
test at several thicknesses (coats) and look for that spot that is 'wow'!
We carefully measure the specific gravity of the test batch and then shoot
for the thickness of the wow spot. Every batch has specific gravity checked
every time it is used. Otherwise you're just shooting in the dark. (As has
been discussed here before, this is true specific gravity testing, not done
with a hydrometer). I suspect those old masters could feel the thickness of
the glaze, knew the thickness of application to less than a TC butt hair.
And generally the glazer was a specialist. No one else need apply.
It all depends on a constant hand. If I glaze our pots they look different
than if Betsy glazes them. I do 2 dips with loss of sheen between, she does
2 immediate dunks. So she does the glazing. They all (mostly) look alike.
It is tough work, made tougher if you don't do it every day.
Tom Wirt
Hutchinson, MN
twirt@hutchtel.net
www.claycoyote.com
Sam Kelly on wed 31 may 06
[SNIP] i agree, but the first time i used an oxyprobe i was amazed a
quarter of an
inch, with the damper, was the difference between oxidation and reduction,
what a learning tool, it gave me understanding, completely changed the way
i
fired. spent about a thousand dollars for it at the time, was well worth
it.[SNIP]
Mate I am with you, I rebuilt a second hand kiln, spent AUD$850-00 on an
oxygen probe and have never looked back, kept firing logs and I can
predict the outcome of the firing even before I light the burners. Time is
money, I have to produce pots, and clients will collect my functional ware
to match the pots they purchased weeks/months ago.
To me glaze thickness is an issue of water content of the glaze slop, 100
grams(%) of a weighed out test glaze mixed with 100mls(cc) of water and
away you go(starting point), test it, add another 50mls of water and see
the difference. 98% of the time the 100/100 as above is not changed. I
fire at cone 9/gas/0.66reduction.
Sam Kelly.
Australia
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