John Baymore on wed 9 jul 97
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I've had trouble with regular pyrometers getting
squirrely over cone 8, so figured I'd use my MOST accurate tool for this
job.
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About a year ago (plus or minus a few months) a long discussion was held
about potters pyrometers. Check the archives.
Cheap pyros have a poor plus or minus figure for the meter unit , and type
K thermocouples are not even rated by ASTM for the temperatures involved in
cone 8-9-10 usages. Adderd together, and you get a unit that is of limited
usefulness.
For cone 9 firing, you should be using platnium/ platnium rhodium
thermocouples and =22meter to match=22 if you need any accuracy at all.
They're expensive, that is why most of the pottery supply places and mfgrs.
utilize cheap type K units.
BTW... the oxyprobe uses a platnium thermocouple.
Best,
........................john
John Baymore
River Bend Pottery
22 Riverbend Way
Wilton, NH 03086 USA
603-654-2752
JBaymore=40Compuserve.com
David Woodin Set Clayart Digest on thu 10 jul 97
The temperature range for type K themocouples is 32 to 2300 F. Most
Industrial pyrometers are scaled 0 to 2400F. Industry would use Platinum
Type R or S, but most potters can't afford them. I have used type K
sucessfully for cone 9 with excellent accuracy and reliability. But you
must use a protecting tube. The manufactures state that reduction will
attack the exposed wire. Industry would never use a thermocouple without a
protecting tube. Most Ceramic suppliers sell protecting tubes. I use an
industrial metal protecting tube that will last for about 80 firings and then
fail along with the themocouple. Ceramic tubes are rated as high as 3450 F
but have no mechanical shock strength. That is why I use a small O.D
thermocouple that gives accurate readings until it fails immediately. At
the NECCA show in Las Vegas some kiln manufactures were using the small O.D.
thermocouple with their new programmers.
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