In direct and hot sun the water can dry out faster than it can run off the glass too.
Gravity doesn't have quite enough time to do its work.
I'm going to do a post about the last house I cleaned yesterday, and post a few pics too, though it is more about the speed you can work at rather than anything else.
However; as I was wandering around taking pics afterwards, and timing this and timing that, 4 or 5 of the windows that were in the direct sunlight had dried out (brown UPVC frames) so I checked them over and low and behold they had spots on them.
After several muttered swearwords I went and got my applicator and squeegee and started to go over them.
But the sun was at an angle where it was blazing full on them, and the squeegeed glass was showing kicks and lines, not excessive of course, but I could see them.
So I thought, 'Sod it
and quickly pulled out the pole and washed these 4 or 5 windows again with WFP (less than 2 minutes for the 5 windows by the way and I did a couple more at either side too, all in under 2 minutes)
It was my last account of the day (2.30pm but that took me to £150 so was happy to finish early) so I washed the van with my WFP to kill a couple of minutes while I waited for the windows to dry off completely.
Checked them over when they had and they had dried out perfect.
Wandered around the rest of the bungalow and they were all fine too, perfect in fact.
It was only those few that were getting the full effect of the warm sun, no doubt the brown frames also added to the heat they absorbed.
My own technique for getting around this probelm is a high flow rate (I always have one anyway) and to quickly wash the window, do a couple to the one side and then go back and do a more thorough wash.
I've found that works fine, and I never rinse with the brush OFF the glass either!
Always leave it on there but rinse with the bristle tips just touching the glass.
Works for me anyway
Time taken to clean this bungalow,18 windows including a large, 10 window conservatory?
12 minutes.
plus 2 more minutes to rectify spots.
Was going time how long it took to wash and squeegee the ones with the spots for a comparison for time, but just the one window was taking way longer and the finish wasn't good enough.
Almostthe entire 50 metres of hose was needed for the whole house and from finishing the last window to closing the doors on the back of the van added 2 minutes to the job.
If I hadn't had to redo those spotty windows, the total time for the job would have been 14 minutes. with 2 minutes added on for the spotted windows.
2 minutes were required to re-clean those windows and as only about 15m of hose had to be pulled out it it took less than a minute to wind in and shut the van doors.
The 10 window conservatory took under 3 minutes, and that included frames and sills too.
I'll post pics in a different thread, but as I mentioned it, I thought I would give an outline in this thread anyway.
Ian