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safety glass: It is a type of glass that, when struck, bulges or breaks into tiny, relatively harmless fragments rather than shattering into large, jagged pieces. Safety glass may be made in either of two ways. It may be constructed by laminating two sheets of ordinary glass together, with a thin inter layer of plastic, or it may be produced by strengthening glass sheets by heat treatment .

In the heat-treatment method, glass sheets are tempered at about 650° C (1200° F), followed by sudden chilling. This treatment increases the strength of the glass sheets approximately sixfold. When such glass does break, it shatters into blunt granules.