Tempered glass - Strain pattern problem

I have the problem with the tempering line. Recently, our products have strain pattern so heavily. I know that is the quench mark. Any advice will help us so much.
Thank you.

Guest User
Sun, 20/03/2016 - 14:12

Iridescence is an integral side effect of the tempering process and is apparent in all tempered glass to some degree. It is seen when polarised (reflected) light hits the surface of stressed glass causing a colour change in the light to appear where the stress level changes.
If the excessive iridescence is in straight lines it is probably a result of all the holes in the quench fins lining up producing lines of high and low stress. If the iridescence can be seen as blotches in lines across the glass then it is because the glass oscillation distance is an exact multiple of the fin spacing (i.e. the leading edge of the glass is stopping at exactly the same point relative to a nozzle (fin) at each reversal point) and the shorter the oscillation distance the more reversals you have before the glass is below the transition temperature (end of quenching).
You will never completely eradicate iridescence, but you can reduce it by adjusting fin alignment, oscillation distance, oscillation speed and having a low index speed into the quench if it is thick glass (6 mm or thicker).

Guest User
Tue, 31/05/2016 - 10:09


I also have problems with strain pattern, but only if we assemble the glass in IG Units.

Both picces were tempered, 8 mm, 3650x2400. First was a Low E and second a solar control glass.

After tempering everything was ok (the recipe is the one we used since 2 years and never had problems), but after we assemble into IG Units the strain patterns were visible with free eye on solar control glass.

I also did tests ajusting the nozzle distance, but the quality is good. No strain patterns visible on single glass. The transfer speed is set almost to the maximum. The quencing pressure is set almost to the lower value.

Can be a bad choise of the glass? Both coated, both tempered and same tikness?

There are rules for chossing the types of glass for IG Units?

Thank you


Guest User
Tue, 31/05/2016 - 14:32

Indecense is ofcourse result of a thermal tempering phenomena. But by adding more holes (in different angles) will almost eliminate not fully but upto 60%. The technic is to reduce the hole diameter and have holes in atleast 5 different angles on each fin and all such fins. This technic is already patented and being used by some furnace manufacturer.

Guest User
Tue, 31/05/2016 - 14:34

Sorry I spelled iridescense as indesence in my previous post

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