I seem to have acquired some marks on the windscreen - they appear to be where the wipers have been parked. The marks have been there some months now and unnoticeable when the car has warmed up, but it's been annoying me for a while.
I always find that a little metholated spirit cleans virtually everything off glass and it evapourates very quickly. In the days when people had to stick rear screen heaters on their cars meths was always recommended as a cleaner before sticking the heated screen on. It is also great for cleaning anything else before applying glue.
I'm not trying to take this thread on to a different subject, but I recently had my car serviced and asked for the windscreen to be treated with what FIAT call "Ducksback" (I think). I must say I am really pleased with the effect of this treatment. One night driving in the dark on the motorway I was aware that it was raining but not enough to put the wipers on. However when I got to a lighted area of the motorway I found that it was persisting it down in huge quantities. But the windscreen was shedding it faster than it came down. I didn't need the wipers on. I found it was very useful especially in the dark areas of the motorway.
I had previously tried applying "Rainex" all round my car but found that needs reapplying regularly. So far after about six months the "Ducksback" (Duxback/Duxbak whatever...) is still working o.k.