Most flameware bodies consisting of approximately half clay and half petalite work well. A higher percentage of fire clay and less of ball clay seems to be the most durable. If a flux is needed to seal the clay body, talc seems to be the best. I cannot include a list of such workable formulae, due on my part to lack of testing and general use of petalite bodies. As soon as petalite became generally unavailable, I began work with a local mineral called spodumene.
Spodumene is quite different from petalite.
It is higher in lithium and iron oxide and lower in silica. In my first test with spodumene this trait became evident. The clay body expanded about two inches and sealed the ware to the kiln shelf above. While chipping at the kiln shelves, I decided that something needed to be changed. Not only did the body expand a great deal, but it was left very porous.