Today.. The clear polycarbonate steam table trays cook more quickly than the amber sulphone ones. But I was not around enough to measure how significant. The glass bowls cook more quickly than the clear polycarbonate. But again, more work is needed to learn if this is a significant difference. The polycarbonate is rated for 210º F. I heated a jar of cooking oil to 250º using the polycarbonate trays. The jar sat directly on the lower surface. There was no melting or any indication of failure. Perhaps the ambient air is cooling the polycarbonate enough to keep the plastic itself from exceeding temperature rating.