Before any clay firing is done, they recommend you put a "witness cone" in the kiln to test how accurate the temperature is reading in the kiln.
You start off with an 05 witness cone.
Put the witness cone onto a shelf in the kiln, in view of one of the peep holes.
We ran a test fire on Cone 05, which tops out at 1,888 degrees fahrenheit.
The whole test took about nine hours! The kiln slowly climbed up to the required temp and when it reached 1,888 degrees, it shut off automatically. Perfect!
|not in the kiln|
A look through the peep hole revealed that the witness cone responded perfectly! If the kiln fired accurately, the witness cone will bend over but not quite touch the shelf. If it fires too hot, the witness cone would bend all the way over and touch the shelf. If it fired too cold, the cone would not bend over very far.
|this pic taken after removing the witness cone from the kiln|
So now, all systems are go!