Aluminium stains on glass windows typically are a result of water dripping down aluminium window trim, siding, eaves or gutters, which leach aluminium into the water. When the drips splash onto windows, they transfer the aluminium to the glass. Additionally, aluminium transfer can occur when aluminium tools or objects accidentally make contact with windows. Aluminium stains give window glass a darkened or silvery streaked appearance. Thankfully, leached aluminium 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 aluminium stain and rub at the stain with a cloth to transfer the aluminium 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.
If dealing with a tough aluminium stain, apply a commercial glass stain removal product onto the stain, wait 10 to 15 minutes--or longer if recommended by the product manufacturer--for the product to break up the stain. Wipe away the product and stain with a soft, microfiber cloth, rinse and squeegee; or, if necessary, scrub the area gently with a nonabrasive, glass-approved scrubbing pad or scrape with a razor blade scraper before rinsing away the product and removing the excess water with your squeegee.
Never use abrasive or harsh cleaners on glass as doing so can etch the glass.