Let's talk a little about the interpretation. We all know it is desirable to use a glaze that is under slight compression. Such a glaze can double the strength of unglazed ware. However, a question presents itself about whether crazing on the samples near the line blend transition point occurred because of thermally imposed or poor fit induced stress. This is pertinent because, while a glaze which is under excessive compression initially strengthens the ware, fatigue and eventual failure can occur because the body is being stretched.
Ceramic materials are very strong under compression but very weak under tension.
A strongly compressed glaze puts the body under tension. Consider, again, a typical graph that plots the strength of a glazed bar against thermal expansion. It would show a steady increase in strength to a fairly wide plateau, then a quick decrease. A point at the beginning of the plateau would provide the desired strength and craze resistance, and also minimize the risk of gradual failure later on. Trying to interpret where the curve peaks by observing our fired samples is not obvious.