Laminated glass was invented in 1909 by French chemist Edouard Benedictus. He fabricated a composite of glass and plastic that was able to reduce the dangers in case of accidents. The invention first was adopted in the glass of the gas masks in use during the First World War.
The laminated glass is made by joining two or more layers of glass alternating with a sheet of plastic, usually polyvinyl butyral (PVB). The PVB is joined with the glass sandwich which is then heated to 70° C and pressed with rollers to expel the air and combine the materials. The operation is ended by inserting the sandwich in an autoclave at constant temperature and pressure.
The intermediate layer keeps the pieces of glass in place even when the glass breaks, and its resistance prevents the formation of large sharp fragments. More layers and greater thickness of the glass means increase its resistance. The bulletproof glass made with many layers of thick glass, can be up to 50 mm thickness. The layer of PVB also gives the material a greater effect of sound insulation and reduced by 99% transparency to ultraviolet light.