Glass Tempering Basics: Avoid These 6 Common Mistakes

  • By:LiaoDA
  • Date:2024-06-03

Understanding the technique is crucial when it comes to glass tempering, much as in cooking. Nowadays, glass tempering machines are equipped with more sensors, allowing operators to extract more data and measurements. To reduce operational errors, they also incorporate further automation.

In the long run, automation will make operating the furnace a little easier. But glass processors still need to do a lot of things right to get high-quality tempered glass. The following is a list of six typical errors that can be avoided when tempering glass:

1. Not Learning Process Basics

You need to know the necessary process basics before you start the operation. Some glass processors skip the basics, which leads to some quality problems in the products they process. Of course, this is not a good situation.

The tempering line is not a magic black box. To be honest, the behavior of glass is relatively easy to understand. If you heat or cool the glass unevenly, it will bend. If you overheat it, it gets wavy. These are the basics that should be clear to anyone operating a glass tempering machine.

Manufacturers often provide customers with basic documentation and training packages that clearly explain operational practices and considerations. Be sure to take the time to learn the process basics! It may take a while, but you will benefit in the long run. For example, if you know the process basics well, you will know which step is wrong and can adjust it in time when there is a problem.

2. Neglect the Quality of Pretreatment

Generally speaking, the tempering line is usually one of the largest investments in glass processing plants, so attention is focused on the tempering line. However, pretreatment, which includes cutting, grinding, cleaning, and other operations, is just as crucial as glass tempering when considering the end product's quality and the volume of manufacturing.

Damage and production quality are directly correlated with the quality of the pretreatment. Sometimes, processing plants upgrade to state-of-the-art tempering lines, but the pretreatment systems remain unchanged and outdated. This has a significant impact on the quality of the finished product. 

For instance, improper edge treatment leads to increased damage to the tempering line, proper edge treatment allows the glass to run at a lower temperature in the heated part, improving optical quality and reducing damage.

3. Maximize Loading Efficiency

A new tempering line purchased by a processing facility almost never causes a bottleneck within the facility. Still, many people are obsessed with loading as efficiently as possible, putting small and large glass plates into the same load, with long and short sides in the same pattern but in different directions.

Mixing loading modes and different glass orientations, short side and long side, will result in different optical qualities. If these glasses are installed as part of the same facade, you will see different optical reflections and will most likely eventually lead to recycling. This is a common beginner mistake. So, avoid it.

Do not be misled, optimizing loading efficiency will increase your energy efficiency and is a good thing. The secret is to never sacrifice on quality.

4. Heating Time is Too Long

In the process of glass tempering, too long heating time can lead to a variety of problems. For example, overheating can cause too much stress inside the glass, which can cause the glass to spontaneously break during or after use during cooling. Moreover, a long time of heating will lead to changes in the surface quality of the glass, such as increased roughness or the formation of defects such as bubbles and inclusions.

In order to avoid these problems, the heating time and temperature must be carefully controlled during the tempering process to ensure that the glass uniformly reaches the optimal temperature without overheating. Proper monitoring and precise control of the tempering furnace is essential for the production of high quality tempered glass.

5. Handle Thick and Thin Glass in a Similar Way

Handling thick and thin glass in a similar way during the tempering process can cause serious problems, as different types of glass have different thermal properties and requirements.

Don't place thick glass in a furnace that is extremely hot. You don't want to hear "Boom!" we assure you. That's the sound of thick glass shattering in a furnace used for tempering. Heat shock is the cause of the breakdown in this instance. To prevent a temperature that is too high or too low, it is therefore best to regulate the temperature in accordance with the manufacturer's instructions.

In addition, uneven tempering could result from using the same cooling method to cool glass with varying thicknesses. For example, thick glass necessitates a slower, more regulated cooling procedure. The same procedure that is used for thin glass may not provide enough cooling, which may cause internal tension and even failure.

6. The Wrong Way to Eliminate "Ghosting"

"Ghosting" is a term used to describe a visual defect that occurs during the glass tempering process. It is typically caused by contaminants, roller residues, or uneven heating or cooling.

Attempts to remove ghosting by incorrectly adjusting the heating cycle, for example, can exacerbate the issue or introduce new defects. Uneven heating can result in new stress points or glass deformation, and overheating can cause surface defects like bubbles, inclusions, or more ghosting.

The proper method is to precisely calibrate heating and cooling cycles and use sophisticated temperature monitoring systems to identify and correct any uneven heating or cooling patterns.


It's no secret that as our work becomes more routine, we make more mistakes. The more you think you know about something, the more likely your choices will lead you down the wrong path. That's why even the greatest experts should always keep the basics in mind.

Please feel free to consult us with any questions you may have about glass tempering, and we will be happy to provide you with professional answers.




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