#AskGlaston Episode 11: What are the main reasons for thick glass breakage?

Glass breakage in the tempering furnace is something that we all want to avoid. In this #AskGlaston episode, we are looking at the factors that can lead to the breakage of thick glass in a radiation furnace. The other question refers to the difference of heat-strengthened and tempered glass.

For this week’s questions, see our full video response below. As always, remember to learn, share and succeed!

What are the main factors that can lead to thick glass (15 mm and 19 mm) breakage in a convectional radiation furnace?

Thick glass breakage may be caused by heat transfer that is too large at the beginning of the heating process. This is caused by convection, which is too high, or then the heating power used in the beginning of the heating cycle is too high. Both of these factors, or either one of them, causes thermal shock that breaks the glass.

What is the difference between heat-strengthened (HS) and tempered glass? Why would I order heat-strengthened instead of tempered glass or vice versa?

The main difference between HS and tempered glass is how it breaks. Tempered glass breaks into very small pieces, whereas heat-strengthened glass breaks into larger pieces. The difference comes from the tension level in the glass.

As regards differences in applications for HS and tempered glass, tempered glass is always used when it is required by safety norms. If there is a regulation for safety, tempered glass naturally has to be used. Heat-strengthened glass should be used instead of a normal float glass in places where the safety aspect is not as important, but where there might be a chance that the glass is exposed to thermal load.


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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.