Hammered aluminum is often found on old decorative pieces. People often think that aluminum does not tarnish or corrode, but it can and does. Cleaning and polishing aluminum takes a special technique---though standard metal polishes often will not do the trick.
Apply a generous amount of the wheel cleaner to your rag.
Rub the wheel cleaner onto the hammered aluminum piece in circles until it turns black.
Continue to rub the black off, using clean sections of rag, until the surface of the aluminum gives off nearly no more black.
Spray the whole surface of the aluminum with Windex.
Wipe the remaining black off the aluminum with the paper towels.