Tempered glass is also called toughened glass. Unlike annealed glass, tempered glass breaks into small, square pieces when broken. This makes it less likely to lacerate a person that comes into contact with it. Tempered glass is one of the hardest types of glasses, several times harder than most others, including annealed glass. Creating tempered glass involves the use of chemicals and heat to give it its properties. These treatments balance the internal stress rating of the glass.
When glass is annealed, it is slowly cooled to relieve any internal stresses. When not annealed, glass is more likely to crack when exposed to temperature chances. Unlike tempered glass, traditional annealed glass will break off into large, sharp shards when broken. This can pose obvious safety risks. Care should be taken when choosing locations to install annealed glass. Make sure to follow any local codes and laws when deciding to use glass for your projects.
Tempered glass is more expensive than annealed glass because it has to go through more processes in its creation. Despite its shortcomings when compared with tempered glass, annealed glass is still widely used because of its low cost.