Frameless shower doors are made of tempered glass that is stronger than regular glass and reduces the risk of injury if it breaks.
Frameless shower doors are constructed with tempered glass, or safety glass, that is often 3/8 inch thick. This glass is specially treated to reduce the risk of injury if it should break.
Tempered glass is four to five times stronger than standard, or annealed, glass. When annealed glass breaks, it forms jagged pieces that can cause cuts and injuries. Tempered glass, however, breaks into small, oval-shaped pebbles when it is broken. The shape and size of the pieces reduces the risk of a person being injured if he or she is struck by the glass. Tempered glass breaks in this way because the tempering process puts the outer surface of the glass into compression and the inner surface into tension.
Tempered glass is treated with a process of extreme heating and rapid cooling to make it stronger than ordinary glass. It can be manufactured by heating annealed glass to around 620 degrees Celsius (1,148 degrees Fahrenheit). The glass is placed on a roller table, taken through a furnace, and then rapidly cooled with forced air drafts, while the inner part of the glass is free to flow for a short period of time.
Tempered glass can also be manufactured through a chemical process. A surface layer of the glass at least 0.1 mm thick can be forced into compression by immersing the glass in a bath of molten potassium nitrate. This leads to an exchange of sodium ions with potassium ions in the surface of the glass and makes it tougher.
Tempered glass must be cut and any holes must be drilled before it undergoes a heating or chemical treatment process. Cutting or making holes in the glass after it is treated could cause it to break.
Due to the balanced stresses in the glass, damage to any part of it can eventually cause the glass to shatter. The glass is most susceptible to damage along the edges, but it can also shatter from an impact in the middle of the glass or if the impact is concentrated. It is therefore important to be careful when opening and closing the shower door and not to hit the glass with any type of hard object.
The use of tempered glass does not affect the styles available for frameless shower doors. Tempered glass does not alter the appearance of clear, tinted, or acid-etched glass patterns.
Tempered glass is used in many other applications. The thermal process used to treat the glass makes it heat-resistant. This makes tempered glass useful in applications where it will be exposed to heat, such as carafes in automatic coffee makers and windows in ovens. Tempered glass is also frequently used in computer screens, skylights, door windows, and the back and side windows in automobiles.