Steel wool

Just like to add - not using blades will not mean that you won’t have any scratches. Strip-washers can also pick up debris & do the same damage, or even release the glass fines to cause the scratches - get them waivers signed!

Well said Karl!

Its the only time I’ve ever scratched a window (that I know of) - with a strip washer!

I thought it was a lack of non-water (minerals, etc.) content that causes a glide issue.

Try running pure water on a dirty glass surface without scrubbing, then hit with your scraper/blade – no glide despite its lack of cleanliness.