[Brent Hollen]

A good window cleaning contractor will determine, prior to project start, if cleaning can be done safely, without risk of damage to the windows.
Scrapers and razor blades, when used properly, won’t scratch uncoated glass and are effective at removing construction debris. Plastic scrapers, however, are not recommended because fabricating debris can become embedded into the plastic during the scraping process and will scratch every window it comes in contact with from that point on.

[Richard Norfolk]

What you failed to do there Brent is actually give an answer to your thread title (not having a pop mate ).

The golden rule is never to try and scrape dry glass, always make sure the area you want to scrape is wet and kept wet. This combined with using a good angle and not stabbing or hacking at the glass will ensure a nice easy scrape with no damage. Glass is not a smooth surface, contrary to popular belief, so wetting before scraping gives you the lubrication you need to prevent damage and clean the window effectively.

Not a text book answer but you get the drift

[johnny bravo]

scrape in one direction only, usually downwards at an angle., wet first 

[Londoner]

Rule 1 - Don't do builders cleans
Rule 2 - Don't do builders cleans
Rule 3 - You guessed it

[[GQC] Tim]

What you failed to do there Brent is actually give an answer to your thread title (not having a pop mate ).

The golden rule is never to try and scrape dry glass, always make sure the area you want to scrape is wet and kept wet. This combined with using a good angle and not stabbing or hacking at the glass will ensure a nice easy scrape with no damage. Glass is not a smooth surface, contrary to popular belief, so wetting before scraping gives you the lubrication you need to prevent damage and clean the window effectively.

Not a text book answer but you get the drift

Using a fresh scraper blade on a dry relatively clean pane of glass will not scratch it, guaranteed. Try it. It all depends on what material you are removing from the window. I always dry scrape silicone or sealant off windows. Backwards, forwards, doesn't matter, as long as the angle is kept right. With mortar and such I wet the window with soapy water and do only one pass in one direction at a time, then clean the blade.

[PoleKing]

Use a proper glass cleaning blade that will need replacing more often but will scratch less.

Never use a stanley blade-theyre too strong

www.laneswindowcleaning.com