Glass fencing is made from tempered glass that is stronger than other types of glass and is less prone to breaking. This creates a fence that is both attractive and safe. Tempered glass is used in many other applications where there is a high risk of human contact, such as windows, doors, showers, table tops, and desks.
Tempered glass is more impact-, heat- and scratch-resistant than non-treated glass. Both types of glass can be made in a variety of sizes, thicknesses, and colors.
Tempering puts the outer surface of the glass into compression and the inner surface into tension. If the glass is broken, those stresses cause it to shatter into thousands of small, granular pieces, rather than jagged shards that result when plate glass is broken. While this can create quite a mess to clean up, it does not cause sharp edges that could injure someone.
In order to manufacture any glass, sand, soda ash, and lime are mixed and melted at very high temperatures. This liquid is then blown, pressed, or drawn into glass. After that, the glass goes through an annealing process in which it is reheated and cooled to restore its strength and prevent it from shattering. The rate of annealing, or cooling, determines whether the glass will be standard or tempered. Standard glass is cooled slowly, while tempered glass is cooled quickly.
Tempered glass must be cut to shape before it is treated. Once tempered glass has been treated, it cannot be cut or it will shatter into thousands of pieces. After the glass has been cut to the appropriate size, the edges are belt-seamed or sanded to remove any sharp or jagged pieces. Then it is washed to remove any leftover debris. After that, it is heated to about 1300 degrees Fahrenheit and immediately cooled to create the tempered effect.
Glass can also be tempered by treating it with hydrofluoric acid or another acid, which etches away surface scratches and imperfections to increase the strength of the glass. Another method involves immersing the glass in a bath of molten potassium nitrate. This chemical process creates glass that is stronger than tempered glass strengthened by heat.
Tempered glass is four to five times stronger than untreated glass and just as smooth and clear. The only sure way to tell the difference is to look for a tempered glass stamp.