glass tempering

The tempering process is what makes glass tough, hard to break, and resistant to heat. However, the quality of tempered glass can be impacted by the tempering process itself, the environment it is in, and even how it’s handled after being tempered. This is why it is important to understand how to maximize your tempering process for the best results.

Tempering is the process of heating a sheet of glass to high temperatures to create a thermal gradient within the glass, increasing its strength and making it less prone to cracking. The result is a glass that can withstand higher impact loads and bending than un-tempered or soft glass. It is also safer to handle, as it will shatter into small, rounded pieces rather than large sharp ones.

The earliest methods of tempering were experimental in nature, with different temperatures and times being used to try and find the best mix for glass strength and durability. Corning physicist Jesse Littleton’s experiments in the 1920s led to his discovery of the ideal temperature range for tempering glass and laid the groundwork for flat-glass tempering that is still used today.

During the tempering process, a sheet of glass is heated to the “annealing point,” a temperature that is high enough to make the glass firm but low enough for stress to relieve during the cool down. Once the annealing point is reached, the glass is soaked or held at that temperature for a period of time to allow any stress to be relieved.

Next, the glass is quenched to cool it. During the quenching process, the exterior of the glass cools much faster than the interior. The difference between the cooling of the outer and inner surfaces gives tempered glass its strength by creating tension-opposing forces that make it stronger than un-tempered glass.

Once the tempered glass is cooled, it is ready for cutting and finishing. It is important that the glass is cut to the correct size and shape before it is tempered so that the edges don’t have a sharp edge. If the edges are too sharp, the glass is prone to breakage and can cause injuries if someone accidentally touches it. It is best to use a cutting machine that can both cut and edge the glass so that the sharp edges are taken off and the surface of the glass is smoothed out.

Another common mistake that can be made is trying to increase loading efficiency on a tempering line by increasing the heating times in order to decrease glass waste. This will not only decrease the loading efficiency but can also affect the quality of the glass because the longer a piece of glass is heated, the more it will become stressed during the cool down phase and may break. In order to minimize this effect, a glass manufacturer should ensure that they are not mixing short and long side leading glasses into the same load.