Certain types are also an excellent protection against hammer- or blow-torch-wielding burglars. This is due to the fact that the various layers of glass are separated by one or several elastic films made of a synthetic material called polyvinyl butyral (PVB). Pressure and temperature during manufacturing are such that PVB layers become almost permanently bonded to the glass.
Laminated glass is more easily cracked than tempered glass, but much harder to pierce thanks to the PVB film. When it breaks, it cracks in a star pattern, whereas tempered glass shatters. Another difference is that, contrary to tempered glass, laminated glass can still be sawn, cut or pierced after the manufacturing process has been completed.