Hank Murrow on fri 14 jul 00
>For some time now I have been using an Axner OxyProbe to assist in our raku
>firings. After gaining some experience with the probe I find that I still
>have some questions about its operation that are not addressed in the
>operating instructions. I wonder if others who use this tool would be able
>to help?
****As a kiln manufacturer/mostly potter, I can share from my 18
years experience with the OxyProbe(or KilnFinger, as irreverent friends
call it), which are standard issue on my kilns.
>
>1) My readings are negative numbers. That is, I see -0.7 in heavy reduction,
>not 0.7. Is that right? The instructions imply that the readings should be
>positive.
****Your readings are negative because they are telling you how
much less oxygen is in the kiln atmosphere than the outside (ambient)
atmosphere.
>
>2) I find the zone between neutral and heavy reduction to be _very_ narrow.
>The meter jumps from about -0.2 to -0.6 or -0.7 almost immediately. There
>seems to be no such thing as light reduction for me. Is this typical?
****I find a similar jump in the readings. What I have learned to
do is watch the flame coming out of the flue exit as to strength and color
to fine tune neutral. In my lifting fiber kiln it is very weak blue/green
flame at the flue. YMMV. You did not say what millivolt range your raku
firing was; but at lower temperatures the Probe IS a bit fluky.
>
>3) With a fixed burner pressure and position, fixed damper position, fixed
>everything that I can think of, reduction increases as temperature
>increases. Is this actually what is happening? Am I seeing an artifact of
>the low temperature at which I am firing?
****If you look at the chart which accompanies the instrument you
will find that the curves for reduction(%oxygen) vary with temperature.
This is built into the instrument; and not a fault.
>
>4) If I turn off the gas, the meter continues to indicate a reducing
>atmosphere for some time (I'll try to quantify this tonight). How can that
>be?
***In my kiln the gas takes awhile to burn off after the valve is
shut. You can speed this up by not fully closing the damper; but you may
get a stronger pop when gas burns back in the burner.
>TIA for your help.
****I DO hope this has been helpful. My advice to clients who use
my kilnis is to fire the best way they know how for three fires and just
mark down the numbers. After three fires you can then 'fire by the #s'.
Hank in Eugene
>
>Bruce "if I could only get a reduction atmosphere for my middle" Girrell
>
****Tell me about it, We go to the gym three times a week and the
flab is just getting stronger!
Bruce Girrell on fri 14 jul 00
For some time now I have been using an Axner OxyProbe to assist in our raku
firings. After gaining some experience with the probe I find that I still
have some questions about its operation that are not addressed in the
operating instructions. I wonder if others who use this tool would be able
to help?
1) My readings are negative numbers. That is, I see -0.7 in heavy reduction,
not 0.7. Is that right? The instructions imply that the readings should be
positive.
2) I find the zone between neutral and heavy reduction to be _very_ narrow.
The meter jumps from about -0.2 to -0.6 or -0.7 almost immediately. There
seems to be no such thing as light reduction for me. Is this typical?
3) With a fixed burner pressure and position, fixed damper position, fixed
everything that I can think of, reduction increases as temperature
increases. Is this actually what is happening? Am I seeing an artifact of
the low temperature at which I am firing?
4) If I turn off the gas, the meter continues to indicate a reducing
atmosphere for some time (I'll try to quantify this tonight). How can that
be?
TIA for your help.
Bruce "if I could only get a reduction atmosphere for my middle" Girrell
Bruce Girrell on mon 17 jul 00
Hank Murrow wrote:
> ****If you look at the chart which accompanies the instrument you
>will find that the curves for reduction(%oxygen) vary with temperature.
>This is built into the instrument; and not a fault.
I looked at the instructions that came with my probe and I do not see this
chart. I have the temperature vs. millivolt chart, but it mentions reduction
readings only at a few specific temperatures. Is there another chart that I
don't have or am I missing something?
Thanks for your help
Bruce and Lynne Girrell in northern Michigan
where our very most favorite pot sold on Saturday. Very mixed feelings about
that. Second to most favorite _almost_ sold, too - and we don't even have a
photo of it yet.
Pierre Brayford on mon 17 jul 00
AIC (in Australia) have a website which includes charts.
http://www.cof.com.au/useoxy.htm
Pierre Brayford http://www.ukpotters.co.uk
> Hank Murrow wrote:
>
>> ****If you look at the chart which accompanies the instrument you
>>will find that the curves for reduction(%oxygen) vary with temperature.
>>This is built into the instrument; and not a fault.
>
>I looked at the instructions that came with my probe and I do not see this
>chart. I have the temperature vs. millivolt chart, but it mentions
reduction
>readings only at a few specific temperatures. Is there another chart that I
>don't have or am I missing something?
Jonathan Kaplan on tue 18 jul 00
>Date: Tue, 18 Jul 2000 06:53:56 -0500
>To:bigirrell@microlinetc.com
>From:jonathan@csn.net (Jonathan Kaplan)
>Subject:Re: OxyProbe readings
>
>
>We use an AIC oxyprobe that we have used for years. Got it from Nils who
>knows when. Works fine. I also understand he worked with Howard to develop
>their probe.
>
>Our readings are consistant from firing to firing.
>
>We have a fairly sophisticated flame rectification system on a failrly
>simple forced air system. Once the burners are set with the proper air/gas
>settings, the only thing we manipulate is the damper for reduction. We try
>to fire with as much excess air as possible, using the probe as well as
>the charts provided to achieve this. Up to cone 08, we fire with a hard
>excess air flame.
>
>The probe reads about .55 at cone 08 for body reduction. There is
>consistant pressure from the peep holes at the door and the sides of the
>kiln. The charts show this to be still in the excess air area, moving
>towards neutral.
>
>We adjust the damper after body reduction and the probe starts to climb as
>the temperature increases. It levels out at .61-.65. These numbers provide
>us with the surface we need on our wares. There is a green flame showing
>from the peep holes.
>
>What is interesting is that at these atmosphere numbers as well as analog
>temperature numbers, we are still firing clean according to the AIC charts
>Yes the kiln is reducing. There is never any smoke or that funky reduction
>taste inthe back of your mouth.
>
>As a side bar, we fire with natural gas and the cost for our 50 cubic foot
>car kiln is in the neighborhood of $12.00-$15.00, depending on the density
>of the stack.
>
>Jonathan
Jonathan Kaplan
Ceramic Design Group LTd/Production Services
PO Box 775112
Steamboat Springs, CO 80477
(970) 879-9139 voice and fax
http://www.sni.net/ceramicdesign
UPS: 1280 13th St. Unit13
Steamboat Springs, CO 80487
John K Dellow on thu 4 nov 04
Ivor and Olive Lewis wrote:
>Can anyone who possesses and uses an Oxyprobe help me out on this one
>Consulting readings given by an Oxyprobe Table I find that if the maturi=
ng temperature of the clay is 1100=BA C and the probe reading is 3 the ox=
ygen concentration is said to be 0.0001.
>Can someone tell me the units for this value. Is it milligrams of Oxygen=
per kilogram of clay, millilitres per cubic metre of kiln atmosphere. Pa=
rtial pressure of Oxygen in millibars or some other sort of dimension. Or=
is it just a arbitrary dimensionless number.
>Any wise information would be appreciated.
>Best regards,
>Ivor Lewis.
>Redhill,
>S. Australia.
>
>________________________________________________________________________=
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>
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>
> =20
>
Ivor,
why not go to Australian Oxyprobes web site and ask them .
John
--=20
John Dellow "the flower pot man"
From the land down under
Home Page http://www.welcome.to/jkdellow
http://digitalfire.com/education/people/dellow/
Ivor and Olive Lewis on thu 4 nov 04
Can anyone who possesses and uses an Oxyprobe help me out on this one
Consulting readings given by an Oxyprobe Table I find that if the =
maturing temperature of the clay is 1100=BA C and the probe reading is 3 =
the oxygen concentration is said to be 0.0001.
Can someone tell me the units for this value. Is it milligrams of Oxygen =
per kilogram of clay, millilitres per cubic metre of kiln atmosphere. =
Partial pressure of Oxygen in millibars or some other sort of dimension. =
Or is it just a arbitrary dimensionless number.
Any wise information would be appreciated.
Best regards,
Ivor Lewis.
Redhill,
S. Australia.
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