Pottery will crack or break into pieces whereas glass will crack or shatter into pieces, is one way of describing it. The difference is that pottery is “cemented” (glued) together and glass is “fused” together via a molecular bond. One can get “cut” on a piece of broken pottery but it is the sharp edge of the “glass” glaze that is the culprit.
Anyway, glass is not a good conductor of “heat” but it will expand when it gets “hot”. Thus, depending on the “color” and the ”shape” of the glass object, …. if it is subjected to direct Sunlight then that portion of the glass will “heat up” and expand before the rest of the glass does …. and thus is likely to either crack or shatter. HA, just like most cooks know better than to drop a “hot” glass object into cold water. “Thermal shock”, I believe its called.
