Paul Herman on sat 10 dec 05
Hi Eric,
Trust the cones first. They measure "heat work". Pyrometers measure
electrical current generated by a thermocouple.
My experience is that pyrometers are only dependable for telling you
if the temperature is going up or down. I use the K probes, and have
never tried a platinum thermocouple, which is more dependable I hear,
but expensive. Last time I bought K thermocouples, they were about
$12 each. There are some extras in the shop in case one fails during
a firing, which they have several times. Have you tried a new one?
Best,
Paul Herman
Great Basin Pottery
Doyle, California US
http://greatbasinpottery.com
On Dec 10, 2005, at 5:10 PM, Eric Suchman wrote:
> I was wondering which is more accurate...... cones? kiln
> sittercones? or analog pyrometer?
Eric Suchman on sat 10 dec 05
I was wondering which is more accurate...... cones? kiln
sittercones? or analog pyrometer?
My pyrometer seems to be several cones lower than my large cones and
kiln sitter cones seem to designate. Is there a way to calibrate the
pyrometer or does this mean that there may be a problem with the
thermo-couple?.... or something else. My glazes, few that they are,
( M^6 recipes all), are turning out fine.
Any help or insight would be appreciated.
Thanks,
Eric in Oceanside
William & Susan Schran User on sun 11 dec 05
On 12/10/05 8:10 PM, "Eric Suchman" wrote:
> I was wondering which is more accurate...... cones? kiln
> sittercones? or analog pyrometer?
What we are most concerned with in firing our ware is heat work, not a
specific temperature at a specific time.
With this in mind, the pyrometric cone is our most accurate measurement of
heat work. Cones will provide you a reading of how the heat has "worked" on
the ware. Speed of firing will affect the results. Even if one uses a
programmable controller, I consider witness cones a must, if for no other
reason, that there will be a record of the firing to help diagnose any
problems.
Small cones (better to use the bars) used in the kiln sitter will also
measure heat work, but there is also a rod pushing down on the cone, so most
folks place a cone higher than their firing temperature to compensate for
this. The problem with a kiln sitter is that it is a mechanical device that
can get out of adjustment or simply fail (failure usually due to unusual
melting of cone or something stuck in the porcelain tube, I've seen both).
The pyrometer is good for watching the rise and fall of temperature. Using
one with two thermocouples on my Olympic updraft kiln is critical for me to
obtain an even firing. The accuracy of the reading is dependent on the
quality of the equipment, especially the thermocouple.
All three are useful for firing, and I recommend using all three, ALL THE
TIME. If I had only one available, I'd select large cones.
I'd also suggest a 4th part of firing, keeping an accurate record of every
firing.
-- William "Bill" Schran
Fredericksburg, Virginia
wschran@cox.net
wschran@nvcc.edu
Eleanora Eden on sun 11 dec 05
For a long time I didn't bother with cones. My pyrometers SLOWLY
moved out of whack and finally I capitulated and went back to cones.
Now I use cones at the peeps and cones correspondingly in the center
of the kiln. I draw the cone packs (fairly accurately) on the firing
record.
So when I am firing I am referring to the last several firings of
that type, looking at how the cones looked as I was reaching
temperature and my conclusions about that firing. I find this helps
enormously.
The pyrometer readings wander around a bit. But with the cones for
high-point accuracy the pyrometers add a lot of information
especially for early part of firing and indispensable for cool-down.
Eleanora
>.
>
>I'd also suggest a 4th part of firing, keeping an accurate record of every
>firing.
>
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