iandol on mon 19 feb 01
I am sure that were I a manufacturer seeking to exploit the consumers =
discretionary dollar by producing and marketing pottery I would wish to =
obtain maximum profits through efficient use of all resources, which =
would include fuel and power. So I would have my employees use =
instrumentation such as the Oxyprobe.
Now, at this point, I have to assume that this instrument measures the =
degree or concentration of oxygen in a kiln atmosphere. Am I correct in =
believing that it does not measure the gas which is considered =
responsible for causing reducing reactions on clay and glaze chemicals? =
We assume that because we use a carbonaceous gas, liquid or solid fuel =
that a low measure of oxygen means a high concentration of carbon =
monoxide. No reason why that should not be so is there? But an oxyprobe =
tells us nothing about that gas!
Consider the following Thought Experiment.
Imagine mounting an oxyprobe in the chamber of an electric kiln. It will =
always give a reading which indicates a high concentration of oxygen. =
But now change the atmosphere. Pump a gas into the chamber. Not a =
flammable gas. Choose a relatively inert one, argon or nitrogen. Less =
hazard that way. As gas is admitted the dial on the oxyprobe will show a =
decline in the level of free oxygen and the value will drop to a reading =
which, in a carbon fuelled kiln, would indicate excellent reduction. =
Oxygen has been replace by an inert gas but the values say we are =
getting reduction.
If the stream of gas is continued as the kiln cools we prevent =
re-oxidation. The resulting pots are outstanding examples of copper red, =
iron celadon and even that rare violet which sometimes occurs with =
titanium loaded glazes.
A Caveat for those who may wish to turn this thought experiment into =
reality. You may not get these results for there is nothing in our =
potters instruction books to validate my supposition. It may be that =
those who fire to cone 6 in electric kilns would be disappointed when =
electric reduction by such a simple means seems within reach, without =
any drawbacks. Higher temperatures may be needed to get these reactions.
Also, though I dislike applying such terms as acidic, basic and =
amphoteric to the chemicals we use in silicate glaze recipes because of =
the concepts they imply relating to chemical activity which may not be =
appropriate I suspect that Silicon, a notable reducing agent, may have a =
greater part to play in Glaze Chemistry than that ascribed to it by =
current ceramic reduction dogma. I also suspect that Carbon monoxide =
does not do the things which are attributed to it, in terms of glaze =
chemistry.
Ivor Lewis. Redhill, South Australia
Steve Mills on tue 20 feb 01
The pros and cons Oxyprobes is quite an interesting subject. In the days
before they made their appearance, we used to use a very simple means of
gauging the atmosphere in our fuel kilns, to wit a smouldering twig held
by the spy hole; if the smoke from it was sucked in, we judged it to
have little or no reduction, if it went straight up: neutral, if it was
blown away from the spy: we had (we guessed, usually accurately)
reduction. it was a very simple technique and for us produced consistent
results.
Are we getting too technical, or am I just a latent Luddite!
Steve
Bath
UK
In message , iandol writes
>I am sure that were I a manufacturer seeking to exploit the consumers =3D
>discretionary dollar by producing and marketing pottery I would wish to =3D
>obtain maximum profits through efficient use of all resources, which =3D
>would include fuel and power. So I would have my employees use =3D
>instrumentation such as the Oxyprobe.
--
Steve Mills
Bath
UK
Karen Sullivan on tue 20 feb 01
Steve...
I use this technique to read the back pressure in the kiln...
So you are saying that the back pressure is related to reduction????
Could you describe the theory more.
many thanks
bamboo karen
on 2/20/01 3:15 AM, Steve Mills at stevemills@MUDSLINGER.DEMON.CO.UK wrote:
> The pros and cons Oxyprobes is quite an interesting subject. In the days
> before they made their appearance, we used to use a very simple means of
> gauging the atmosphere in our fuel kilns, to wit a smouldering twig held
> by the spy hole; if the smoke from it was sucked in, we judged it to
> have little or no reduction, if it went straight up: neutral, if it was
> blown away from the spy: we had (we guessed, usually accurately)
> reduction. it was a very simple technique and for us produced consistent
> results.
> Are we getting too technical, or am I just a latent Luddite!
>
> Steve
> Bath
> UK
>
>
> In message , iandol writes
>> I am sure that were I a manufacturer seeking to exploit the consumers =3D
>> discretionary dollar by producing and marketing pottery I would wish to =3D
>> obtain maximum profits through efficient use of all resources, which =3D
>> would include fuel and power. So I would have my employees use =3D
>> instrumentation such as the Oxyprobe.
>
> --
> Steve Mills
> Bath
> UK
>
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Jonathan Kaplan on tue 20 feb 01
on 2/20/01 10:28 AM, Karen Sullivan at kwinnies@EARTHLINK.NET wrote:
> Steve...
> I use this technique to read the back pressure in the kiln...
> So you are saying that the back pressure is related to reduction????
> Could you describe the theory more.
> many thanks
> bamboo karen
Correct indeed.
The sensor,on the tip of the probe, at least on the AIC probes available
from Nils is designed to read the partial pressure in the kiln, basically
reading the amount of O2 present. When the amount of O2 present is
decreasing, the signal is increasing. And visa versa. The sensor generates a
signal that is in turn, read by the digital meter and using the charts
supplied by the probe manufacturer, you can determine where your kiln is
firing....excess air, neutral, or reducing.
Manipulating the damper is also changing the amount of 0xygen present in the
combustion, hence, a reducing atmosphere.
We have used a probe since 1984 or so. It has provided us with accurate
readings yielding dependable, reproducible firings time after time.
Jonathan
--
Jonathan Kaplan
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
jdkaplan@cmn.net
Plant Location (use for all UPS, Common Carrier, and Courier deliveries)
1280 13th Street
Steamboat Springs CO 80487
Steve Mills on wed 21 feb 01
Karen,
In a word, yes. For all my production life I used natural gas kilns, my
mate Michael used on oil fired kiln initially, natural gas after that.
In both cases we achieved reduction by removing bricks from the chimney
thereby slowing down the speed of the gases exiting the kiln. Propane
kiln firing Potters achieve the same results by pushing of the damper
in. Either by leaving the gas settings as they were, or increasing them,
we achieved reduction (back pressure) by inducing a fuel rich atmosphere
inside the kiln. For the majority of my work I used quite a heavy
reduction which was easy to gauge by the length of flame (post 1100
degrees centigrade) coming out of the spy hole. On occasions however I
would need a lighter reduction and that is when the twig came into play;
as with no visible flame the amount of pressure inside the kiln was
difficult to assess, however the smoke from the twig was a perfect
indicator. Another Potter named Guy who works locally needs a neutral
atmosphere to achieve the colours that he wants. In his case the smoking
twig is the best, and possibly the most accurate indicator.
Steve
Bath
UK
message , Karen Sullivan writes
>Steve...
>I use this technique to read the back pressure in the kiln...
>So you are saying that the back pressure is related to reduction????
>Could you describe the theory more.
>many thanks
>bamboo karen
>
>on 2/20/01 3:15 AM, Steve Mills at stevemills@MUDSLINGER.DEMON.CO.UK wrot=
>e:
>
>> The pros and cons Oxyprobes is quite an interesting subject. In the day=
>s
>> before they made their appearance, we used to use a very simple means o=
>f
>> gauging the atmosphere in our fuel kilns, to wit a smouldering twig hel=
>d
>> by the spy hole;
--
Steve Mills
Bath
UK
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