Both ceramics and glass are inorganic materials. Though each of them has different melting temperatures and surface tensions. When fusing glass, it is important that each piece shares the same coefficient of expansion. Here that is not the case, I am fusing glass on a ceramic piece I have fired to cone 04 and glass fused on at 800 and cooled gradually. Expected!! fusion glass got cracks. The clay surface remained the same. I have been reading about the difference between these firing temperatures. Firing schedule or/and the thickness of the fused glass would benefit the outcome.