You know when you can feel something on the glass though the bristles when cleaning a first or second floor window, but can't see anything? Maybe it's some brick acid, or some spots of pva type stuff.
Do you get the ladders out and have a look or just leave it?
I did a new customer on Friday and could feel something but it wasn't visible. Customer has just text me saying all was ok apart from this particular window {could feel it over most of the pane}. Just wondering what others do.