Tempered glass is a kind of safety glass that gets treated through a process of tremendous heating and fast cooling; thus, making the glass harder than normal glasses. The cooling process determines whether the glass is tempered or standard. Tempered glass is made to cool quickly while the normal glass is made to cool slowly. Tempered glass is known to be four to five times stronger than a standard glass and is also called as toughened or strengthened glass.

Tempered glass is more heat resistant and scratch resistant compared to standard glass. The process that makes tempered glass heat resistant is called the thermal process. Tempered glass is made in different sizes and thickness and can also be tinted just like any other types of glasses.

To create any type of glass, sand, soda ash and lime are mixed together and melted at very high temperature. By using the methods of blowing, pressing, or drawing, a hot liquid is formed into glass. After the glass is shaped, it will go to a process of heating and cooling called annealing. This process keeps the glass from crushing and restoring its strength, so tempered glass and standard glass differs greatly in the way they are being processed.

When tempered glass breaks, it explodes into little pebbles pieces. Standard glass breaks into large sharp shaped edges. Thus, tempered glass is much less dangerous to those coming in contact with it. With this brittle nature and along with its strength, tempered glass is frequently referred to as safety glass. Standard glass will break in the particular area which will result in cracks or damage in one location only, but still can make the rest of the sheet intact, while the tempered glass is more crash resistant, but can shatter at once thus leaving no intact areas.

Tempered Glass History

It was believed that in the early 1900's that Tempered glass was developed. The first patent is said to be held by Rudolf Seiden, an Austrian chemist who immigrated to the United States in 1935. Pittsburgh Plate Glass Co. was the first one to develop Herculite tempered glass in 1938, but stopped producing it within a few years as the company focused on regular float glass.

Tempered Glass Types

To make a tempered glass, there are two processes being used:

• Vertical tempering: The glass is being held in a vertical position by using metal tongs to move through the furnace. There are marks of tongs left on the edge and will not be seen after the frame has been installed in the glass.

• Horizontal tempering: This is the most commonly used method of tempering glass today. In a horizontal position it moves the glass through the furnace through the use of rollers. This leaves a slight wave caused by the rollers but not visible enough for the observer to notice.

Tempered Glass Uses

Tempered glass can be found almost everywhere nowadays. For examples, tempered glass is found in glass coasters, computer monitors, liquid crystal displays (LCD), skylights, refrigerator shelves, oven door, door windows, tub enclosures and shower doors. This type of glass is used to make the carafes in automatic coffee makers. Nowadays, many public structures, such as bus stops, as required by Building Codes to use tempered glass windows.

Some manufacturers also use tempered glass for making their baking and cooking products.