If you have metal window frames or screens and you've noticed the glass window panes have become hazy, or have developed a white, etched appearance, it's likely the glass has become oxidized. This process initially affects the metal when it is exposed to humid or wet conditions, and then spreads to the glass. Normal window cleaning procedures will not remove these stains. However, specialist cleaning products designed to deal with the problem are available.
Wring out a cleaning rag in warm water, and apply a little of your chosen oxidization removal product to an inconspicuous part of the window. If no adverse reaction occurs, it is safe to proceed with removing the oxidization from the rest of the glass.
Apply your oxidization removal product to the stained areas of the window. Pour a small amount onto a clean damp rag, sponge or nylon scouring sponge, and use circular motions to work it into the area of discoloration. Continue rubbing until it becomes dry, then wipe off any excess with a clean, dry towel.
Wash the window thoroughly with warm soapy water. Rinse it with clean water, and use the squeegee to remove all moisture. Washing neutralizes the oxidization-removing chemical you used. Wash, rinse and squeegee the window a second time to be sure all traces of chemical are gone.
Inspect the window to ensure all areas of oxidization have been removed. If any still remain, repeat the process, starting with the application of the oxidization removal chemical.