Look around your local hardware store sometime, in the glass section, and you will find "glazing compound," used to seal the glass in the window frame (simple explanation.)
The plastic in your windshield (which is between two layers of glass) is there to prevent something hitting the windshield from coming all the way through (or you from going out, if you have an accident and neglected to fasten your seatbelt). If you score and break both sides of windshield glass, the joint will flex. Common alcohol can then be used to disolve the plastic and complete the "cut". By itself, the plastic would be of little use as a window.
An extreme example of the hazing that occurs between the layers can be seen at "The Henry Ford," in Dearborn, MI, where several presidential limos are on display. The windows of the Reagan limo are completely frosted over - the result of the phenomenon Mr Harmon speaks to. There is a placard at the display explaining why the windows are "frosted. "
