#AskGlaston Episode 42: Why does a diamond-shaped pattern sometimes show up?

This week, we are dealing with the following question:

Why does a diamond-shaped pattern sometimes show up when the glass is exposed to steam, for example when humidity is very high?

For this week’s question, see our full video response below!

I have seen in some glasses a diamond-shaped pattern that shows up when the glass is exposed to steam, for example when humidity is very high. Why this happens?

In the picture, we can see the diamond pattern visible in the glass when there is a humid environment, so there is some steam on the glass.

Most likely, this is caused because in the diamond pattern itself, the steam reacts differently to the glass than on the actual marks on the diamond pattern. That would then indicate that there are some residuals from the tempering process that create this pattern.

Now if we check the tempering line and see the Kevlar cording, we will notice that this is actually in line with the pattern. So most likely the reason here is that the Kevlar cording leaves some sort of residual on the glass which then is visible in the humid environment.

There are things that can be done in order to minimize this. One is to make sure that the glass is as clean as possible and make sure that there are no any other impurities in the glass. Impurities increase the probability of this kind of issues to happen.

There is also a possibility that the glass may have been stored for too long. Or maybe there are some oil residuals in the Kevlar cords, which can cause this phenomenon to happen. Or it is also possible that the silicone that has been used to attach the Kevlar cord has been absorbed onto the surface of the glass. And also some mechanical variations in the chiller rolls could cause this kind of phenomenon to be more visible in the glass.

Check these things if you are having challenges with this issue.

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About the author

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.