How to remove cement water stains from glass?

[starfish4]

We had roof repaired a few years ago, and cement has mixed with rainwater and stained one of our windows? Any idea how to remove it? I've tried soapy water, glass clean.

Have you tried limescale remover?

Wd40?

Green Klean cement & mortar remover from Amazon.

Spirits of salt.

I think it has probably etched the glass and will not come off.

try a test area with an acid cleaner. Even vinegar will do if you are just trying to break down/dissolve the cement. Or you could use Viakal. If it is working it will fizz or bubble and you can wipe it away with a wet sponge. Do not try to clean glass dry as it will be scratched.

If this does not remove it, the glass is etched.

Look on the bright side, reglazing a window is easier and cheaper than you think. There will be at least one small business in your town doing it (double glazing goes misty after 10-20 years so there is constant demand)