firstly, this stain only appears when the glass is steamed up or when the glass gets a bit dirty. When immaculately clean, it doesn't show at all. It is like a film on the surface of the glass, which throws water off or makes it go into beads. It has been there since we stripped the wallpaper in that room using a steamer. The steamer was used above the window and we did see the paste and other dirts running down the glass, but thought nothing of it. when the room was fully stripped, we even steam cleaned the UPVC frame around the window to remove the yellowness and years of dirt i guess. the glass got a steaming too. nobody noticed at first, but i think when we first noticed it was steamed up. it looks like run marks, coming from the very top of the glass, but you can see through it.

it looks awful, so we tried all sorts of substances to try to get rid of it including petrol, nail varnish remover, and meths, all sorts of things we found in the garage. nothing has worked, and to be honest, the window will need replacing because it looks onto our grounds.

any advice very much appreciated and will be tried. thank you.

hardmanphil

Hi chain smoker.
Firstly this depends on the glass you have installed. In recent years most household glass windows are actually coated with a chemical during manufacturing. This could be somthing to reflect heat back into your room, anti-fogging or just an easy clean coating. Whatever it is it sound like this coating has degenerated in this area. A combination of hot steam, chemical leached from the wall paper paste or the uPVC have attacked the coating, possibly removing it or causing a chemical reaction that has changed it's properties. So as such I doubt that it is actually a stain. The chemicals you have used would readily remove the types of stains you get on glass, it's just a case of finding out what your glass was coated with originally if you stand a chance of restoring it. Completely uncoated glass is slightly porous to some chemicals under some conditions. It is also possible that chemicals based on oils and waxes in the paint on the paper you were stripping have soaked into the glass, again pretty much unrecoverable.