This year I am plagued with cracking tiles. We've made them
twice; they have cracked both times. I dry them slowly between
two sheets of plywood so they stay relatively flat. The cracks
are not at the edges, but through the centers. I cut the slabs
myself from my little slab cutter from a 25 lb block of clay.
Slabs are 7/16" thick. Kids use square templates and cut the
square tiles from their slabs.
They are breaking before the firing! And sometimes a little more
cracking during the firing! These are the same as I've made for
years, same thickness, same method of cutting. The only change
is the clay. I'm using this year's clay supply (and it is the same kind
of clay!!! low-fire white!)