Hi Pres and Chris and Marcia. Many thanks for your insights. I found the camera, and attempted to upload photos. Okay, I don't know how to upload photos to this forum. I tried including them from Word and got an error message. Could you please instruct me on how I can include the photos?
I'd never heard of bloating. (Down side of being self taught). It's a great word to describe what I see.
Let's see. Marcia: Glaze run is to cone 6 ramped quickly on my manual L&L 1970's kiln with kiln sitter, two rings, two knobs, low medium high -- setting knobs simultaneously to each setting with about 70 minutes in between clicks. Glazes are Amaco Potter's Choice PC-33 Iron Luster cone 5/6 (shades of brown) and one from our local shop Leslie's Ceramics Supply Niji Purple Cone 5 brushing glaze.
Bisque (over a year ago) and while I keep a record of how I fire, I'm not certain which load these two came from. Best guess looked like: 1230 lower ring on low, upper ring off, lid propped and lower ring peep hole plugged, upper peep open.
1530: low and low, 1845: Med and low. 2015: med and med, lid closed, open peep still open. 2115 hi and med 2230 hi and hi and both peeps plugged.
Next question if this is bloating, can you describe what's happening and the clincher: how to prevent it in a manually fired kiln?