Window scratches which can be seen when the sun shines through the window are, unfortunately in most cases, permanent.
Inexperienced painters using sand paper and electric sanders on window mullions which divide the window panes.
Use of razor blades to remove paint and stickers from windows.
The window glazed surface is very thin and over time use of abrasive paper and ammonia will degrade transparency of window by creating
micro- scratches that cause a hazy surface.
Although modern architectural glass is very strong and can resist high winds, the production process in which the glass is heated to over 900 degrees and rapidly cooled using air makes the surface softer and the cooling air can embed grit into window surface. Use of blades or abrasives should be avoided or only by trained window cleaners.
Often after we clean your windows and they are transparent, these scratches are visable, which is a result of one of the above actions. If you have any doubts after we complete the windows I can actually show you the mechanism of injury to your windows.