History of glass in automobiles.

Brief history of auto glass

Gasoline automobile manufacturing started to take off in the early 1900s.  By 1919 glass had become an integral part of the automobile.  In the beginning auto glass was simply annealed plate glass (the same glass used in most home windows).  That glass was not nearly as safe as today’s auto glass.  Annealed glass will break into large dangerous chards when impacted.  This created a huge liability problem for car manufactures.  Pressure from lawsuits and the people prompted the federal government to raise the bar for glass use in automobiles. 

Federal regulations spurred the invention of two different types of safety glass used in autos today, tempered and laminated.  Laminated glass is mostly used in windshields.  Laminated glass consist of a triple layer, two sheets of glass bonded a centerpiece of plastic lamination (the two pieces of glass sandwich the lamination).  The triple layering strengthens the glass and holds it together when impacted.  The plastic inner layer protects occupants from two dangers.  First, the lamination prevents rocks and other road debris from penetrating the glass and injuring vehicle occupants.  Second, the inner plastic layer is powerfully bonded to the glass; the lamination holds the glass in place so large chards of glass do not fall into the laps and faces of occupants.  Voila! You are much, much safe due to laminated safety glass.

The second type of safety glass is tempered glass.  Tempered glass has two properties that keep vehicle occupants safe.  The first is its’ strength.  Tempered glass is about 15 times stronger than regular annealed glass.  The second safety feature of tempered glass is how it breaks.  Tempered glass breaks into hundreds of tiny chards of glass.  The small pieces of glass cannot inflict serious injury or death like large chards of glass can; damage from tempered glass breakage is usually limited to scratches and/or glass splinters.  Voila!  You are again protected by innovation. 

The federal government requires the Department of Transportation (DOT) safety ratings are clearly marked on all auto glass today as DOT 15 (other numbers exist) and AS1 or AS2.  AS1 stands for Auto Safety rating 1, laminated glass.  AS2 stands for Auto Safety rating 2, tempered glass.