The thermocouple measures the temperature of a kiln. The thermocouple is two wires of dissimilar metal welded at the tip. When exposed to heat, the thermocouple creates a very small voltage, measured in millivolts. The millivolts of a thermocouple are even smaller than the voltage produced by the human body.
A temperature controller reads the millivolt signal and converts it to a temperature.
The K-type and S-type are the most widely used thermocouples in glass fusing, ceramics, and jewelry kilns. 95% of the kilns in America have the K-type, and only about 5% have the far more expensive S-type.
The S-type thermocouple normally doesn’t wear out, and as it ages, it does not “drift” in temperature. Its connection block would corrode long before the thermocouple itself would wear out. If the S-type fails, it is almost always because of mechanical breakage due to rough handling, such as hitting the thermocouple with a shelf while loading the kiln.
Should you ever break an S-type platinum/rhodium thermocouple, don’t throw it away. If it breaks at the welded tip, it can be repaired by a fine jeweler or by the Orton Ceramic Foundation. (Orton makes S-type thermocouples.) Orton charges about $45 to weld the tip. Note: Welding a broken tip may shorten the thermocouple by 1/4” (6.25 mm).
In the last Kiln Pointer, I included a story entitled “The Critter That Ate Greenware.”
Dave Coggins wrote, “Your reader's story reminded me of the time my wife made some lovely hand-sculptured chess pieces in white clay and left them uncovered to dry. The next day she was horrified to see that several of the chess pieces' faces were missing. The answer was obvious--nearby there was a very large mud dauber wasps' nest beautifully made from white clay!
“We have also unknowingly fired pieces with mud wasps' tubular nests inside,” Dave added. “They fire up quite well. Here in sub-tropical Queensland, Australia, potters have lots of critters to live with. In my kiln repair days, I have had to rebuild several fibre-lined gas kilns which had been used as a safe, warm home by bush creatures. They came in through the uncovered burner ports or flue, and burrowed into the fibre, although I imagine they would have had a few digestive problems from ingesting the fibre.”
“Read an hour every day in your chosen field. This works out to about one book per week, 50 books per year, and will guarantee your success.” --Brian Tracy
News: The New 12-sided Oval Glass Kiln
Last week we added the Ovation-1213 glass kiln to our website along with its CoreLite furniture kit. This is our largest oval glass kiln. It comes with two of the new, extra heavy duty 32” square x 18” rolling stands.
to see the kiln.