Advice for increasing time, decreasing temperature to reach cone 6

[Nancy Talanian]

Thank you, Mark.  I will take your advice and put at least a few unadulterated cone packs in the kiln.

[Nancy Talanian]

 

16 hours ago, Dick White said:

Nancy, I have an ancient Econo kiln, to which I have added an external controller. I also have a separate thermocouple/pyrometer harnessed to a computer with a logging program with which I can create a minute-by-minute profile of the actual firing performance. I have found that no matter the ramp schedule I program into the controller, the old kiln can only manage around 100F per hour at the very end coming into cone 6.  So, with your new kiln which has the power to actually produce the higher ramp rates of even the "slow" cone fire final ramp, you are firing hotter and faster than before. Knock your final ramp rate down to 100F/hour and watch the cones to decide when to manually turn it off. You'll probably find cone 6 bends at 2175F or maybe even lower. Once you've tuned in the ending temperature, you can incorporate that into the final program segment.

Dick, thank you!  That was exactly what I was thinking, and you've confirmed it.  When I had the same kiln, I manually read the one pyrometer, and I have no written record of a temperature above 2150.  The thermocouple was in the top third of the kiln.   The rises may have sometimes been even slower, because although we're supposed to have 240, sometimes we had only 220 or even 215.

Based on your experience, for my next glaze firing, at around 1800 or 1900F, I will slow down to 100F/hr. and just shut off the kiln when cone 6 is down throughout.   Sound good?  I really appreciate your input!

[Nancy Talanian]

On 2/4/2019 at 8:07 PM, Min said:

Also, try putting a test pot with the proper looking glaze in a bisque firing. If it comes out muddy like the one above I would put it down to too slow a cooling. Just try one change at a time. 

Bingo!  Although the glaze on the pot was thin, at least it was blue.  Second photo shows the same pot bisqued to 05.  So, slow cooling due to 3" bricks not only muddied the glaze but may have accentuated the 3% RIO and 6% light rutile, obliterating the 1% cobalt carb and 0.75% copper carb.  To counteract this tendency in my next glaze firing, I'm planning a slow rise toward the end, shutting off the kiln when cone 6 drops.  But Min's right that I should try only one change at a time.  If the slow rise isn't enough, then my next move will be to cool the kiln shed with a fan and perhaps even pull one or more peeps out after 2 hours.  Hmm.  Maybe the reverse order.  So many variables, yikes!