Traditional Glazing Glass is a mixture of silica (Si02), soda (Na2O), and lime (CaO), with trace iron impurities from sand (silica). These fundamental ingredients are augmented by regulated additions of various 'impurities' to obtain particular qualities, such as boron (borosilicate glass) for heat resistant applications like laboratory glassware and Pyrex, or silver and copper for photo chromic uses. Because of its amorphous molecular structure, glass is fragile and lacks ductility, and it gives little or no notice when it is about to fail. Surface imperfections that are too small to discern with the human eye might occur during manufacturing and handling, compromising the strength of the glass. .
