How to specify the right glass in terms of surface quality for your project?

How to specify the right glass in terms of surface quality for your project?

From time to time, I get questions from glass structural engineers about specification advice on glass quality for high-profile facades. How they can make sure they will get the best possible or most suitable glass quality for their project? The challenge is if they overspecify, all glass suppliers will decline to quote. If they underspecify, they will not get what they want. Many times, the question is: what is the best I can realistically get from the market?

Not all projects require the best possible glass quality. I like to talk about the most suitable glass quality. Still, many glass processors rely on industry standards like EN 12150, which, to be frank, has very loose quality criteria. If you get glass that is just at the limit to pass EN12150, you will most likely not want to put that on your building. The key is to recognize the most important criteria to specify and make sure the criteria fits your particular project plans.

The glass tempering and heat-strengthening process always create some deviations in the glass. The deviation that is acceptable depends mainly on the place of installation. If the glass is on a high-profile facade, make sure you have very tight requirements for the glass quality. If it’s interior glass where the distance of observation is much shorter, the surface quality criteria is not as tight.

Here is some advice on how to specify if you want to be sure you will receive top-quality glass in terms of surface quality – and that the good processors in the market are also able to deliver.

This example specification is for 6 mm glass:

  • Rollerwave: the peak-to-valley (depth of the wave) deviation should not exceed 0,08 mm
  • Edge lift: the peak to valley in the 300 mm area from the edge should not exceed 0,2 mm from the leading of trailing edge
  • Over all bow: the maximum acceptable should be in the area of 1,5 mm/m, including both bow and warp

If your supplier declines to commit to these values, consider other glass sources. If you are a glass processor and have difficulties reaching these specifications, you may want to take a look at:

how to reduce rollerwave in tempered glass

– how to heat-strengthen thick triple-silver glass

And if these don’t work, it is worth taking a look here.


Will this work for your project? What are the tightest specifications you have requested or you have been asked to quote for?




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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.