As those in the commercial and residential construction industry know, tempered glass is nearly 5x stronger than regular annealed glass. Tempering means heating the glass to extreme temperatures and rapidly putting it through a high-pressure cooling process.
This procedure puts stress on the glass, which in turn produces tension that begins in the center of the piece and spreads out. The tension is then compressed on the outer edges, which gives the glass sheet its strength.
How is glass tempered? Here's a “behind the scenes” look at the five-step glass tempering process.