#AskGlaston Episode 27: What is the root cause of a rainbow effect and how to avoid it?

This week, we are dealing with the following two questions: 1. Recently, we got a complaint about 6 mm clear toughened glasses that were installed as windows in a hotel. The complaint was about a rainbow effect all over the areas. Can you help us – what could be the root cause of this problem? 2. I’m running a PRISMASOLAR profiled glass, and the structure of this glass is very deep. The glass always comes out sad, bending towards the structure on the top. How can I fix this problem? For this week’s questions, see our full video response below! As always, remember to learn, share and succeed!

Recently, we got a complaint about 6 mm clear toughened glasses that were installed as windows in a hotel. The complaint was about a rainbow effect all over the areas. Can you help us – what could be the root cause of this problem?

This rainbow effect is called anisotropy. And every tempered glass has this kind of image. You can see this image with polarized filters, such as sunglasses, or sometimes even with naked eyes in certain light and conditions. With new tempering technologies like full convection, you have tools to control and minimize the effect. There are lots of excellent articles and presentations about anisotropy here in Glastory. So if you're interested in the subject, you can learn more about the phenomenon itself as also how to minimize it.

I’m running a PRISMASOLAR profiled glass, and the structure of this glass is very deep. The glass always comes out sad, bending towards the structure on the top. How can I fix this problem?

PRISMASOLAR is a very challenging type of glass. The challenge comes because there’s such a big difference between the surface area of the glass on the top and the bottom. In this particular type of glass, you have a much bigger surface on the top area. This means that when heating, the top area absorbs the heating more – the more surface you have, the more it absorbs the heat. The similar principles apply in the cooling section but vice versa. As you have much more surface area on top than on the bottom, so it also absorbs more cooling in the quench. If you’re running your line with very standard settings, it means that your glasses will come out sad very easily. So, to correct the situation, start with the quench and adjust the air balance between the top and the bottom pressure by increasing the bottom pressure. That’s the first thing. And then you can also look into the furnace and check that the glass goes nicely into the furnace and adjust the heating settings if needed.

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