***WARNING! The following content is likely to bore non-potters to tears***
Well, for what’s its worth, my very first glaze firing (this is a test, this is ONLY a test) is almost under my belt. Amazingly, everything fit! I am following the firing schedule suggested by John Hesselberth and Ron Roy. The trick is that, having never fired to cone 6 in my kiln, I had no idea what temperature to set it to so that I could include the recommended soak (i.e, not have to skip the soak and start the cool down when I hit temperature). In my quest to figure out how to fire my first cone 6 firing, I found this very helpful exchange on Clayart:
On Jul 25, 2005, at 1:40 PM, Charanjiv Sachar wrote:
> Should it be such that Cone 6 should bend at the end of the 20 minute
> I know it will take a few firings to program it the way the cones
> should bend. But when should Cone 6 bend? or it doesn’t matter and it
> is a matter of how I want the glaze to look?
> I might have just answered my question.
> Thanks in advance to everyone
Unfortunately there is no fixed answer to your question. Every kiln is
a little different and thermocouples drift a bit as they age. With my
kilns I find somewhere between 2170 and 2195 usually does the trick.
But when I am firing with a new thermocouple or in a kiln I am not
familiar with I pick a temperature at the upper end of that range. Then
I watch the witness cones and when cone 6 gets to about 2 o’clock I
note the temperature, turn the kiln off and quickly enter a new program
that has that temperature as the peak, the soak I want, and the cooling
cycle. Then turn the kiln back on. It shouldn’t take more that 2-3
minutes and the kiln won’t drop more than 15-20 degrees. Then if the
cone bends to almost tip touching during the soak I just use the ‘skip
to the next ramp’ capability of the controller and start cooling a
little early. All this just requires you be thoroughly familiar with
how to program your computer–but that’s not such a bad thing to learn.
Then in future firings you will be much closer and, gradually, you will
get your program fine tuned to where the computer does the whole job.
You will have to adjust it a bit, though, every few firings as your
thermocouples age. Good luck.
Following John’s advice, I set the target temperature on my program to 2195. I also programmed a second program, with a “full steam ahead” (9999) ramp up to 2185, with the required soak, then the controlled cooling ramps. Knowing how anxious (and sleep-deprived) I’d probably be during the firing, I figured it would be quicker to change just one number in the program when the time came rather than enter the whole thing.
I started looking at my cones at around 2100F. At 2145F, Cone 5 (my guide cone) reached 1 o’clock. It hit 2 o’clock around 2160F, then finally 3 o’clock at 2165F. At this point, Cone 6 started to move. It reached 2 o’clock at 2178F, at which point I stopped the program, and quickly re-programmed my second program with 2178 as the peak temperature. Whew! A few minutes before the end of the soak, Cone 6 had it’s tip touching, with slight movement starting on Cone 7 (my guard cone). This is what is described in “Mastering Cone 6”. I skipped to the next ramp. So far, so good.
Now, the kiln is going through its controlled cool down (free fall to 1900F, then 125F an hour to 1400F). I have never been so excited nor terrified about a kiln firing before! Hopefully there will be a few nice results. Stay tuned…