Scratched Window Glass - Quality Issue?

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Old 10-26-13, 10:53 AM
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Scratched Window Glass - Quality Issue?

Hello,

So we have removed, refinished and reinstalled many of our homes windows over the last couple of years. This often requires replacing broken panes of glass.

For the last batch of windows, we purchased glass from a hardware store down the street. We have never purchased glass from here before.

We refinished these windows in the same manner as we have in the past, and when finished painting we used a razor blade to scrape off extra paint from the panes. To our surprise, when we held up the windows, the edges are completely covered in scratches. Of all the windows we have done, this is the first time we have found scratches like this.

Are we doing something wrong? Or does this hardware store carry cheap glass?
 
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Old 10-26-13, 01:12 PM
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I don't know if there are quality differences in glass. I had a window cleaner tell me long ago that it's important to only go one direction with a razor blade, that along with using a cleaner as a lubricant goes a long ways toward not scratching the glass.

I assume you bought real glass and not something like lexon or pexiglass.
 
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Old 10-26-13, 01:55 PM
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I don't know if there is much difference in the quality of window glass. There is harder, scratch resistant glass but it's generally not used in residential windows but is commonly used on phones, tablets and computer screens.

Holding a razor or box cutter blade at a shallow angle and scraping or "shaving" across the surface will generally not cause scratching but if you stand the blade up more vertically or hold it at an angle so just the corner of the blade is touching than it can scratch glass. Dirt and mineral deposits on the glass can also cause scratching.

Getting scientific... glass has a hardness of about 5.5 on the Mohs scale which is about the same as a knife blade. Hardened steels like a file or razor blade are about 6.5 so if not careful a razor blade is capable of scratching glass.
 
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Old 10-26-13, 03:16 PM
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Paint contains pigments that are abrasives. Using a razor blade to remove paint is pretty much similar to rubbing the glass with fine grit sandpaper, or rubbing it with a dry powdered cleanser like Comet. I have installed and cleaned windows for many years but have never scratched the glass, but I also always wet the glass with glass cleaner before using a razor blade or scraper to lubricate it... scraping it with a dry razor blade is a sure way to scratch it. I'm sure there are also techniques that are more prone to scratch it, as Pilot Dane mentioned.
 
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Old 10-27-13, 08:41 AM
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Window glass is all the same. What type of glazing compound did you use and how did you apply it?
 
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