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Ok To Use Pyrometer Instead Of Cones?


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#1 TortoiseAvenger

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Posted 04 July 2014 - 07:10 PM

I was recently reading in Mastering cone 6 glazes that you shouldn't rely on the kiln sitter to turn off the kiln. It suggested that it should be used more as a safety device, and that you should hold the temp at the recommended cone for a short time.

Which brings me to my question--how come you hear all this about cones, but never just using a pyrometer? It seems that an installed pyrometer would do the same or even a better job.

Thoughts?

TA

#2 Chris Campbell

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Posted 04 July 2014 - 07:27 PM

I am by no means an expert but ... the temperature of the kiln is not an indicator of heat work. The correct firing temperatures are a combination of heat and time.
This is the same reason why you preheat the oven in your kitchen ... Your heat sensor says it has reached temperature but it is only reading one spot in the oven ... In order to have the correct temperature throughout the oven you need to give it time as well.
The cones and computer programs are calibrated to take these factors in.

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#3 John Hertzfeld

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Posted 04 July 2014 - 07:54 PM

Chris is correct that the air temperature of the kiln is not the measure of heat-work.

The food comparison is good, think about a pizza that you put into a cold oven. You then turn the oven on to 475*F, the pizza will not be done when the oven reaches 475*F. The pizza needs to soak at that particular temp for a good 15 to 18 minutes. Moisture burns off, things melt, and everything on the pizza comes together after just the right amount of time at this temp. It's not always 15 minutes, sometimes longer. That's why you check your pizza to see if it needs longer.

The time at temp is what heat-work is all about. Pyrometric cones are precision instruments that will tell you when your pottery is done, because just like pizza it's no good under or over done.

They are affordable and easy to use, so get one under at and over your target cone level, and get a pyrometer to assess and record the rate of temp increase to help understand what a good firing looks like.

#4 Biglou13

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Posted 04 July 2014 - 08:57 PM

Ok yesterday I fired to 2203 with a 30 min hold. Middle shelf had perfect CONE 6. Five flat. Didn't fire - 7 cone.
2203F is less than cone 6 temp. 30 min hold dropped cone to an appropriate cone 6
Cone 6 should be approx 2232F.
In this case heat , and time @ temp, = cone 6..... Although temp never reached 2232F. I am 29 degrees shy of cone 6.

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#5 JBaymore

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Posted 04 July 2014 - 09:10 PM

Temperatures shown on cone charts are shown as an end point that happens at a certain rate of climb in degrees per houir during the last part of the upward firing cycle.  A cone X does not always melt at Y temp...... it melts a Y temp when fired at Z rate.

 

A "hold" is the equivalent of lengthening the time to a certain temperatue... hence a higher cone # end point.

 

best,

 

.....................john


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