The answer to 'window stain removal' is to first identify the type of stain and then use the appropriate cleaning method. Common window stains include hard water spots, grease, and paint. For hard water spots, a vinegar or lemon juice solution can help dissolve the mineral deposits. Grease stains may require a degreasing cleaner or rubbing alcohol. Paint stains often respond best to a razor blade scraper or chemical paint stripper, used carefully to avoid damaging the window glass.
If the stains are extensive or difficult to remove, it's best to call a professional window cleaning service. They have the right tools and cleaning solutions to safely and effectively remove stubborn stains without risking damage to the windows.