Overlooked posting on the April 2013 firing...went well with good ash on applied-glaze surfaces. My decision was to persue custom clay bodies for the next firing in August as this is an area I would like to explore.
With regard to the August firing...a success. Blended up 10-#150+ batches of clay bodies...all of which were influenced by Jack Troy's recipes. Used Helmer and Tile6 in most bodies...EPK in some and found that bodies with Redart responded well to the firing's atmosphere and temp. range.
I had been resisting a low-temp hold early in the firing for a while and decided that along with the new bodies...we'd try holding around 600F for 12 hours or so. Along with a few other changes in firing technique...we attained the best results so far with the "Pyranhagama". We were super conscious of allowing the atmosphere to clear and oxidize between stokes as we were in the red to orange hot range...this eliminated some spotty carbon coring issues that resulted from over zealous stoking in past firings. Addirionally, we employed a steady heat rise throughout the firing...about 30F/hour throughout the 3.5 day firing (excluding the 600F hold). Finished up the firing with a large stoke followed by a shut down of all stoke and air ports along with the active damper to the flue.
Results were: even ash distrubution throughout the kiln (aside from the very front which gets nailed), ash on horizontal surfaces, subtle directional ash glaze/flashing transitions, Celadon glaze melted more than usual due to increased firing time (cone 12 just started to bend), brighter colors due to Redart/Grolleg clay bodies and small crystal haten families in the ash glaze in shielded areas.