GlassyClass on thu 18 oct 01
Was browsing the REC.CRAFTS.POTTERY Usenet Group tonight, saw something that
was interesting about checking the Oxygen/Reduction atmosphere in your kiln
during firing. Does anyone on the list use such a item as this probe, and
how well does it work if they do ?
http://www.cof.com.au/useoxy.htm
Bud
Hank Murrow on fri 19 oct 01
>Was browsing the REC.CRAFTS.POTTERY Usenet Group tonight, saw something that
>was interesting about checking the Oxygen/Reduction atmosphere in your kiln
>during firing. Does anyone on the list use such a item as this probe, and
>how well does it work if they do ?
Well;
I use one on my doorless fiber kiln (see Sept issue CM, page 42)
and specify them for all the kilns I build for clients. Not only do they
have a superb Platinum thermocouple, but they read atmosphere as well. And
it can be real useful to know the temoperature once the cones have fallen.
However, there IS no substitute for the actual look and smell of reduction
in your kiln.
Cheers, Hank
Marvpots@AOL.COM on fri 19 oct 01
Hi down there:
Yes, I use an Axner Oxygen probe when firing a propane gas-fired kiln and
find that it gives me an excellent guide to the condition of the atmosphere
inside the kiln enabling me to make the adjustments necessary to achieve a
reducing atmosphere.
Axner Pottery Supply can be reached at "axner@ao.net", their web site is
"www.axner.com" and fax # is 407-365-5573 and they are laocated at 490 Kane
Ct., Oviedo, Florida 32765.
I hope this will help you.
Marvin Flowerman
marvpots@aol.com
Dave Finkelnburg on sat 20 oct 01
Bud,
Oxyprobes work very well for helping to fire a gas kiln. It helps if
you understand their limitations. Ivor Lewis in South Australia understands
them better than I and will perhaps add to this.
Oxyprobes are wonderful at helping the potter keep the kiln near a
neutral atmosphere. This avoids wasting gas on a kiln atmosphere which is
too strongly oxidizing or too strongly reducing.
The Oxyprobe measures oxygen in the kiln gases passing the probe. If I
understand this correctly, when you get to strong reduction you basically
have only water vapor, carbon monoxide and carbon dioxide and other chemical
compounds as sources of oxygen inside the kiln. There are practically no
oxygen molecules floating around in the kiln. At that point the Oxyprobe is
not a great tool for telling you how much reduction you have, but it does
give some indication.
If you really want to measure strong reduction, you want to measure the
concentration of CO, carbon monoxide. My understanding is that is done with
a grab sample of kiln gas, so it's not continuous, but has been used in
kilns since at least the 1960's.
The oxyprobe is not cheap, can be damaged by rough handling, and
probably doesn't belong in a salt or wood kiln. That said, if mine fails
I'll repair or replace it immediately!
Good firing,
Dave Finkelnburg
-----Original Message-----
From: GlassyClass
>Was browsing the REC.CRAFTS.POTTERY Usenet Group tonight, saw something
that
>was interesting about checking the Oxygen/Reduction atmosphere in your kiln
>during firing. Does anyone on the list use such a item as this probe, and
>how well does it work if they do ?
iandol on sun 21 oct 01
Dear Dave,
Good contribution. Can't think that there is anything I would wish to =
add to your comments except that carbon monoxide and hydrogen, if it is =
present as a result of that high temperature water gas reaction with =
free carbon, act as scavengers for any oxygen which might be evolving =
from a glaze.
Perhaps it is not a well known fact but at the top temperatures we fire =
to, high silica refractories, in the presence of hydrogen, can become =
unstable in an atmosphere which has no oxygen, . Silicon dioxide is =
reduced to Silicon monoxide which is volatile.
All the best,
Ivor Lewis. Redhill, South Australia.
John Kimpton Dellow on mon 14 oct 02
recently someone mentioned that the oxyprobe reading was bouncing
around
during a firing. Its normal for it to do so in the range of .1 &
.2. This
indicates a good oxygen to gas ratio. More information can be
found with link.
http://www.cof.com.au/aos.htm
John Dellow "the flower pot man"
Home Page http://www.welcome.to/jkdellow
http://digitalfire.com/education/people/dellow/
Bruce Girrell on tue 15 oct 02
John Dellow wrote:
>recently someone mentioned that the oxyprobe reading was bouncing
>around during a firing. Its normal for it to do so in the range of .1 &
>.2. This indicates a good oxygen to gas ratio.
That's OK, but the issue that I have and, as I recall the thread, the issue
that the write had, was that the reading would jump from the neutral .1 - .2
to .6 or so. There seems to be almost no such thing as, say, a .4. There
appears to be a very steep slope between neutral and fairly strong
reduction; you are in one condition or the other, but almost never in
between.
Bruce Girrell
in cool northern Michigan where fall is very late this year. Trees that
should be almost bare are still green. Probably about half have started to
turn color. Crossing my fingers that one good frost will get them all at
once and release the magic.
John Kimpton Dellow on wed 16 oct 02
Bruce Girrell wrote:
>
> John Dellow wrote:
> That's OK, but the issue that I have and, as I recall the thread, the issue
> that the write had, was that the reading would jump from the neutral .1 - .2
> to .6 or so. There seems to be almost no such thing as, say, a .4. There
> appears to be a very steep slope between neutral and fairly strong
> reduction; you are in one condition or the other, but almost never in
> between.
> Bruce ,
does your probe have an air source attached. If so have
you checked that
there is no blockage in the pryo head. Mine once melted the
plastic tube, which
connects a fine metal tube which delivers air to the tip of the
oxy probe. This caused inaccurate readings.
John Dellow "the flower pot man"
Home Page http://www.welcome.to/jkdellow
http://digitalfire.com/education/people/dellow/
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