Heat-strengthened glass will break into medium-sized shards.
Heat strengthened glass is annealed glass that is heated to approximately 1300°F, where it reaches its softening point. It is then cooled to create surface compression. This compression allows the glass to tolerate more rapid and uneven temperature swings.
Heat strengthened glass is approximately two times stronger than annealed glass; however, if impacted, heat-strengthened glass will break into medium-sized shards.