Roger Graham on sun 27 apr 03
Three years back I bought an expensive oxyprobe, to fit in a little test
kiln while I played what-if with copper red glazes. Two years and umpteen
firings later, a friend suggested more experiments with an automotive EGO
(exhaust gas oxygen) sensor, to measure oxygen concentration in the exhaust
gases at the kiln flue. Would the EGO "exhaust sniffer" give the same
information as the expensive oxy-probe?
The experiment results were a surprising success. So much so that I sent off
a description to Ceramics Monthly, to share the idea with whoever else might
like to try. Article appeared eventually (March 2003).
Tonight I thought to look on Google for "kiln exhaust sniffer". Bingo!
There's the complete text of the CM article, pictures and all (
http://www.ceramicsmonthly.org/mustreads/sniffer.asp ) If you haven't access
to CM, but have an interest in oxy-probes, the article is (temporarily) on
line.
If you fire a gas kiln, and haven't already bought an oxy-probe, then this
might be a $20 alternative to get the same information at less expense. Not
included in the printed CM article was a convincing graph, one of a series
plotted from the kiln log during test firings. These showed the rise and
fall of millivolt readings from an $800 oxyprobe inserted in the usual way
deep in the kiln, and a $5 EGO sensor mounted at the flue.
Interested in trying your hand at an exhaust sniffer? I'd like to hear from
anybody else who pursues this line. Can provide a copy of the graph as an
attachment, if you make contact off list.
Roger Graham, near Gerringong, Australia
http://members.optusnet.com.au/~rogergraham
Barry Salaberry on mon 31 may 04
Hi Roger,
My thoughts were different from your conclusions.
It seems to me that when the kiln gets hotter, and the gas and damper =
settings remain static, that the given amount of gas is achieving better =
combustion as the heat rises, thus taking the kiln out of reduction.
In practice, I have watched the kiln get noticeably hotter when I am =
nearing cone 9-10, and I leave the damper where it is, and turn the gas =
down a bit. It does loose some reduction, but my glaze at this point =
has fused well enough to keep the reduction contained, and is not =
affected by the slight shift towards a more oxydised state.
I assumed from your comments that your damper and gas settings were =
constant in your test.
How can you be certain that your level of reduction was constant, and =
that the milivolt output was the "culprit"? Do you have some other =
device which is not affected by increased heat which can measure the =
reduction at all stages?
I find it is very interesting to see how we all think differently about =
what goes on during a firing. =20
Good luck,
Barry
Barry Salaberry
3642 Glencoe Rd.
Westbank, B.C. V4T 1L8
250-768-3268
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