Hi all- I've just encountered a new problem making larger cabochons for jewelry. For years I have made 1/4", 3/8" and 1/2" cabs from 3 mm thick sheet using a schedule that I developed thru trial and error. A few things changed in the past few months: replacement kiln (both Paragon SC2), new batch of shelf paper, and new schedule. Regarding the schedule, I decided to follow the one described in Bullseye "circles from squares" quick tips, thinking I'd be able to fire even larger sizes. No problem with the smaller cabs, but some (not all) of the larger cabs (1/2" and larger) developed a strange disfiguration on the side that faces the back of the kiln. See attached pic.
Re-firing hasn't really helped to round out the shape. I fire so many of these guys that using anything other than shelf paper is a bad option. Is there a better schedule to use?
Many thanks for any tips!