DonC & Jaydee,
I am sorry but Roadrod2000 was right. Windscreens are not manufactured from toughened/tempered glass. They are manufactured using laminated glass which is designed to crack upon impact from projectiles such as stones etc. The polymer interlayer holds the screen intact thereby safeguarding the driver & passenger safety. If the glass was tempered or laminated tempered, it would shatter, and either stay intact and completely block any forward visibility for the driver, or simply fall into the car and hit the occupants as a floppy sheet of broken glass.
Windscreen glass must be laminated plate glass and must confirm to the Federal Motor Vehicle Safety Standards - FMVSS 212 to be precise.
I just needed to clear that up
Stuart