Since you cannot always work on your window cleaning while you have other things to do, you might sometimes leave stains on your windows, stains that over time gather strength in their bond with the glass, making them rather difficult to remove without potentially damaging the glass. Glass stains that refuse to go away even with tough household cleaners require muriatic acid to split the stain from the glass. If you learn how to use muriatic acid, you might save yourself plenty of trouble and actually manage to get rid of the stubborn parts of the stains that just keep sticking onto the window.
Put on a pair of rubber gloves before you begin working. Muriatic acid has highly corrosive properties, making it hazardous to your skin.
Put 1 to 2 oz. of muriatic acid into a gallon of water.
Dip a brush into your mixture and begin scrubbing the window with your brush until you see it noticeably clean.
Rinse the window with pure water and dry it off.
Dip your remaining muriatic acid solution into a drain far away from the reach of children and animals. Do not use a kitchen sink.