[Clayart] pyrometer testing.

David Woof woofpots at hotmail.com
Sat Oct 23 18:51:04 UTC 2021


HI Everyone,

In following this Pyrometer thread, I have only seen mention of the "Thermocouple" once.  And nothing mentioned about the significant part the Thermocouple plays in "Thermocouple Drift" in relation to pyrometer readout accuracy.

All Pyrometers with wires attached depend on the Thermocouple providing an electrical signal.
Which signal changes over time in relation to the Thermocouple's eventual physical deterioration.

Cone packs placed throughout the setting give one the most accurate information regarding the "Time/Temp - Heat Work" the glazes and clay body are responding to for maturation.

FYI....the MINI MAG flashlight puts out more than enough candle power to vividly illuminate the cones firing at cone six.  And is certainly worth having a go at cone 10.

A bending cone pointing to a point on an imaginary clock face indicates what to do next in my firing.

Yet I too have Pyrometers installed on my kilns, but give them a 50-degree margin for error and keep new spare thermocouples ready to go.
Pyrometers can tell me the direction the wind is blowing, but not accurately how many steady knots, or when to drop anchor.

(Try them on a wood firing kiln, follow them faithfully thru each stoking cycle until the White Coats come for you for a ride to the Rubber Room.)

Misneach.

David Woof.................................................................................................................
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________________________________
From: Clayart <clayart-bounces at lists.clayartworld.com> on behalf of mel jacobson <melpots at mail.com>
Sent: Saturday, October 23, 2021 6:20 AM
To: clay art <clayart at lists.clayartworld.com>
Subject: [Clayart] pyrometer testing.

Colleen and I fired both of our stoneware kilns
this last week at the farm.
She fired the big stoneware and I fired the smaller one.

I have done some gas plumbing changes to both kilns, adding
a high temp regulator at the kiln end with a tee connection
to both burners so they each fire the same, all the time.
(much easier to chart as we can use the numbers on the gauge)

We have added high temp regulators at both kiln's tanks.
(jeff from the gas company installed them/ near 40 lbs of pressure.)

The difference in firing speed and efficiency is amazing for both the
big stoneware and the hard brick salt kiln.  We are now under 8 hours for
the salt kiln and in the past it was always 12+.

We used the digital pyrometer on the big stoneware, +cones of course.
I used my older analog pyrometer and the infa-red gun.

Some early results by changing pyrometers around and using the gun
indicates the digital pyrometer as expected was low at cone 11 by almost
30 degrees. My analog was closer but did not give accurate numbers at cone
11.  I fired cone 11 flat, Colleen prefers cone 11 at 2 o'clock.

For around 50 bucks the infa-red gun is a great helper. One has to turn down
the pressure for a minute or so as you do not want back pressure flame. You have
to get close to the peep and aim to the center of the kiln. At cone 9 the gun
read 2321F. Damn close.  It too read low at cone 11 over.

The best news for me is that all three pyrometers give very accurate readings
during the firing. We know when to reduce, when to change settings etc.

I have attached the analog pyrometer to my small kiln with all wiring stapled
in place.  It also has a sign..."Do not move"  "EVER".  I have marked that
dial so that when cone 11 is going over it hits a spot. dead on.

Of course nothing takes the place of cone 9,10,11 for accurate firing.
I am using one analog pyrometer on the electric bisque kiln. It sticks in
place at 2000 but reads well for bisque temps.

I have hammered three analog pyrometers and one digital. In the dumpster.
When we have guests in firing, it was common for them to dig out my old
pyrometers and have them reading the wrong numbers...so out they went.

In talking on the phone to some heat engineers they all agree when measuring
devices start to act up...hammer them. They do not fix. They all agree that
digital is the best, with the infa-red gun as your back up. CONES WORK.
as we all know, engineers work with very high tech
industry with amazing perfection. They never mess with pottery kilns so
we are always the last to know.

And without doubt, all heat measuring devices are very fragile. I like mine
attached to the kiln.
mel
ps, and remember, we as potters are often victims of what your propane dealer
supplies. At times you must argue for more pressure.  It took a long time for
me to become a trusted friend of "Jeff". He now "gets it".  but for many, kilns
are running with house pressure and that means long firings. "often they do not
listen as they don't understand."

I bought $1500 of gas for the winter. and in the last week propane went to
$2 a gallon. I paid $1.21, and it could easily go to 3 bucks. (last July I
paid 92 cents.)

website: www.melpots.com<http://www.melpots.com>
www.melpots.com/CLAYART.HTML<http://www.melpots.com/CLAYART.HTML>

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