Another thing that can leave sparkly dust or salt is when I use my trolly for softwashing. I use the same trolly for window cleaning so the first clean gets some softwash that's let in the hose if I've never rinsed it out. Did one in sheltered housing complex and it was at the furthest point and a bit of a headache to get to. So cleaned with trolly and then realised some hypo still in hose so just cleaned a tad longer thinking the glass will sparkle. Next month she came down and paid me for last month and told me she will clean them herself. Great I thought as it saves me a lot of time.
In the end most of my customers have died, younger fit folk moving in and they have changed the windows to tilt and turn so not worth doing it. Will drag out a tad longer and finally hand over or say I have retired.