Hi all, got a glass conservatory roof in need of cleaning, next door has had a fire and burn't a load of trees and all the ash has gone on the roof then it started to rain so the ash got wet. Anyway the roofs a right mess, tried to clean it 2 day the White ash come off but still lots of marks left on the glass. Used pure water and washing up liquid still no good. Anybody got any ideas what will shift it. pz help