This week, we’re answering to the following two questions:

1. My shower has streaks in the glass running up and down. The issue shows up when the glass gets foggy after showering. Physically, I cannot feel these lines. Can you tell me what causes this effect? The shower glass is only a year old.
2. When testing my 4-mm tempered glass with 1 kg ball falling from the height of 1 m, the glass breaks down. I made this test for all types of products within my furnace, and most glass gets broken. Could you please tell me how can I improve the quality of my tempering process to make the glass pass this test?

My shower has streaks in the glass running up and down. The issue shows up when the glass gets foggy after showering. Physically, I cannot feel these lines. Can you tell me what causes this effect? The shower glass is only a year old.

Most likely, the effect is coming from the tempering process when the glass is in contact with kevlar cords. In this case, the glass surface gets different properties in the areas where the glass was having this contact, and moisture behaves differently in these different areas. This can be seen as lines visible in the humid conditions. These kind of surface differences can be removed by polishing or buffing the glass surface. 

When testing my 4-mm tempered glass with 1 kg ball falling from the height of 1 m, the glass breaks down. I made this test for all types of products within my furnace, and most glass gets broken. Could you please tell me how can I improve the quality of my tempering process to make the glass pass this test?

The way to increase the impact strength of the glass is to increase its tempering stresses. And this you can do by increasing the glass temperature after the furnace or by increasing the cooling pressure during the cooling process. 

One thing to keep in mind is that glass strength against impact depends on how much scratches you have on the surface. So, if the impact is on the roller side, the tempered glass performs much better than if the impact is on the air side. This is because the roller side is expanding the air side, causing the scratches to grow much easier. 

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