Aluminum stains on glass windows typically are a result of water dripping down aluminum window trim, siding, eaves or gutters, which leach aluminum into the water. When the drips splash onto windows, they transfer the aluminum to the glass. Additionally, aluminum transfer can occur when aluminum tools or objects accidentally make contact with windows. Aluminum stains give window glass a darkened or silvery streaked appearance. Thankfully, leached aluminum usually sits on the surface of glass and breaks up easily with exposure to a mild acid and/or light scrubbing.
Clean your glass window with glass cleaner and a squeegee. Spray at the top of the window, sweep the rubber or silicone edge of the squeegee from one side to the other, then down to collect the dirty water. Wipe the squeegee with a cloth and repeat across and down the entire window.
Fill a spray bottle with equal parts of vinegar and water.
Spray the vinegar and water solution on the aluminum stain and rub at the stain with a cloth to transfer the aluminum to your cloth. If you have double-hung sash windows that unhook from the sash to lay flat for cleaning or windows that you can remove from the window frame, lay the glass window flat, spray the surface, wait 10 minutes for the solution to soak into the stain, then rub with a cloth.
Rub undiluted vinegar or a solvent, such as rubbing alcohol, onto the stain if the vinegar-water solution doesn't remove it.
Rinse the window clean with water when finished and squeegee away the excess to give it a nice shine. Follow up with glass cleaner if desired.