Meet the glass tempering beloved child – convection

Think about your friends and colleagues. You can probably easily name the person everyone knows very well. Everybody has an opinion about him or her. That person in the glass tempering business, the kid everyone knows, is convection.

For this reason, it’s not surprising that we, and probably you too, hear people saying: “I want a full convection furnace”, “Is that assisted convection?”, “We want to buy a forced convection furnace”, “Recirculated-air convection provides the best quality”, “Compressed-air convection does not meet my requirements”, “Is this a high convection furnace?”

And the list of convection terms goes on… and on… and on…

We understand that convection is one of the most important things, and it is a good investment. But before we move forward, we have to clarify that there are two main types of convection in the industry:

  1. Compressed-air convection technology
  1. Recirculated-air convection technology

Splitting them into two sections gives you no indication of how they might perform. The titles might give a hint about the technology used to create the convection. But that’s about it.

Rule of thumb?

To be very clear, one technology is not better than the other. Which one to choose is merely an answer to the question: “What do I want to achieve?”

You see, glass does not know what technology is being used to create the convection; it only shows the efficiency of it. So, don’t concentrate on the technology. Concentrate on the result since that’s the only thing that matters to the glass in the end.

The technology used to create the convection does not necessarily correlate with glass quality. Instead, the capability of the convection process does.

Tempered glass quality and glass processing

There is no direct correlation between the technology used to create the convection, regardless of whether it is recirculated or compressed air, and the glass quality. There is, however, a major difference between the different convection systems.

See the difference? The convection performance doesn’t depend on the source of the convection but rather on the entire convection system – measurement, accuracy and control of the full heating system.

“Full”, “high” or “assisted” are simply marketing terms for convection, which are created by tempering line manufacturers. For instance, there are no full convection furnaces because every tempering furnace in the world uses conduction and radiation alongside with convection.

Instead of the convection technology, you need to pay attention to the capability of the convection system – the repeatability, capacity, quality of the glass and reliability of the line.


  • Your tempering line technology should be selected based on your production needs.
  • Don’t concentrate on the convection technology, concentrate on your desired result. It’s most important to choose the solution that provides the best results for you.
  • Recirculated-air convection furnaces are not the same – don’t put them into the same category only based on the similar technology used to create the convection.
  • Compressed-air convection furnaces are not the same – don’t put them into the same category only based on the similar technology used to create the convection.

Psst! We have written a whole eBook on the topic. So if convection furnaces are of interest to you, I recommend that you download the eBook – it’s free!

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Sobre o autor

Miika Äppelqvist

Encourages transparent solutions in buildings and ways of working. Seven years of experience from being a glass-man in product management, sales and projects with a focus on glass heat treatment. Believes helping is the best marketing any company can do. Father of two toddlers and a wannabe sportsman with an internal love of ice hockey.