To those who clean a lot of facia/soffits, whats the best cleaner to use that won't stain glass if it dries on it? I've tried UBIK2000 which definately stains, and a couple of other brands, same story. I've never tried Virosol but according to it's MSDS it has a pH of over 11, which suggests to me that it would also stain glass if left to dry on it. Ideally I reckon a neutral pH cleaner would do the trick, but is there a suitable one out there? Thanks.