If you are among the group of window cleaners that refuse to use scrapers on glass in fear of scratching, you are definitely not alone. However, please know that there is still plenty of glass out there that’s safe to use scrapers on. The critical part is knowing when, and when not to use a scraper. Tempered glass is the most common composite that’s proven to be problematic in the window cleaning world.

So what is tempered glass?

First it is vital to know what tempered glass is, and why does this particular composite of glass often lead to scratches.

Tempered glass is a type of safety glass processed by controlled thermal, or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into compression and the interior into tension. Such stresses cause the glass, when broken, to shatter into small granular chunks instead of splintering into jagged shards as ordinary annealed glass does.

So why is tempered glass susceptible to scratches you ask?

Most scratches in tempered glass are caused by fabricating debris. It is a manufacturing defect that results in low-quality tempered glass and increases the likelihood of scratching the surface during cleaning. This is can often be felt by the window cleaner when dragging your scraper over the glass. More on that later.

According to Scientific American, one of the key steps in the manufacturing of tempered glass is the washing of the glass after it has been cut to the desired size or shape and buffed to take off the sharp edges. Unfortunately, not all glass manufacturers do a thorough job of washing the glass before it goes into the tempering furnace. This, as it turns out, tends to be more common than we would hope.

When dust or debris is still present on the glass when it undergoes the tempering process, they fuse to the surface of the glass. Later on, when the glass is cleaned (you the window cleaner), the debris can be dislodged and dragged across the surface, leaving visible scratch marks.

This was what we were referring to earlier. When running a scraper over the tempered glass which features fabricating debris that has been thermally treated into the glass, this will definitely feel different when running your scraper over it as opposed to glass that has been properly treated.

When glass has been properly treated, aside from the debris you are removing from the glass, it will feel smooth when running the scraper over the window. Therefore, no friction is created between debris and glass to create scratches.

But when you are dealing with glass that has been improperly treated, it will feel a little rougher. It’s almost as if you’re dragging your scraper over some fine grade sandpaper. If you hear, or feel that, immediately stop scraping. It will likely be safest to inform the customer of this and defer to hand scrubbing with glass safe synthetic scrub pad, and or steel or bronze wool. There are glass safe chemicals that can be used safely with scrub pads and or steel or bronze wool we have to offer that can be used to help loosen up tough stains when you are unable to use scraper. You can find a link to these chemicals heremaybe include link to chemicals?)

So how do I know which panes of glass are Tempered?

1. The edging on tempered glass will always be smooth. Whereas Annealed Glass will have rougher edges.

1. Imperfections. Tempered glass will have slight imperfections such as slight bends or grooves in the glass.

1. Use polarized glasses to check. Tempered glass will have dark/shady lines and or spots that will spread across the glass when looking through a polarized lens.

1. The easiest and most effective way to check to see if the glass is tempered or not, is Tempered glass will ALWAYS have an identifier stamped into one of the corners. This stamp shows manufacturer name and the CPSC (Consumer Product Safety Commission) standards, the stamp is a key symbol to give you proof of whether the glass is tempered or not.

It is vital when using a scrapper to be cautious and know what you are working with to prevent scratches. For more questions or comments please feel free to reach out to us at Detroit Sponge. Email us at customerservice@detroitsponge.com or call us at (800) 535-6394. Shop all of our scrapers and other professional window cleaning products on our website.

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