Regular glass, also known as annealed glass, is commonly used for things such as mirrors and windows. During manufacturing, it is cooled very slowly, as to not create tension or compression. Cooling the glass slowly also allows it to be easily cut, reshaped, drilled, and polished. However, regular glass is very fragile and breaks into large, sharp pieces, which can be dangerous.
Tempered, or toughened, glass has become increasingly popular over recent years due to its use in cars, cookware, and mobile devices. Tempered glass is just annealed glass that has been cut to size, reheated, and cooled rapidly. This process makes it much stronger than other types of glass. Although tempered glass cannot be easily cut or reshaped, it is considered safer than regular glass because it shatters into many, many small pieces with more rounded edges. If you’ve ever shattered your smartphone, you can picture the spider-web qualities of broken tempered glass.
Tempered glass is more scratch resistant than regular glass. It is usually the medium of choice for glass tabletops, patio furniture, glass shelves, and skylights because its shards do not commonly cause serious injury. However, because of the extra steps in the manufacturing process, tempered glass is more expensive than regular annealed glass.