Over the last couple of years I have had a few occasions when glaze
just seemed to pop off of clay in small chips. It appeared to go
through most of the firing and meld to the clay, and then chip off in
the cooling off phase. When this occurred it would happen to multiple
pieces in the same firing.
It turns out that this has also been happening to a friend and
colleague at mine at a nearby school. When she presented the problem
to a local ceramic supplier and to reps at Mayco, they tried a
variety of answers, including "the clay must be overworked" (!?!)....
but finally started to focus on firing the clay bodies hotter and
maintaining a larger range between bisque fire temps and glaze fire
temps. I believe the theory has something to do with possible changes
in the clay body over the last few years.
We are both usually using low fire clay bodies and low fire glazes.
She has now moved to bisque firing to 03, and glaze firing to 06, and
has had better results. We both have fairly new kilns (Skutt and
Cress) with digital controls.
Has anyone else had this experience? What have you tried? I will
definitely be following in her footsteps, but it occurred to me that
we are probably not the only ones to have experienced this...and
other people may have additional info or suggestions.
If this topic has already been discussed, please let me know and I
will search the archives. I am somewhat new to the list.