Keeping your cymbals clean and bright is important each new cymbal is tapped by a professional cymbal tester for the right sound. All cymbals when tested new are clean and bright  not dull and dirty ,although some may prefer a cymbals sound that is darker and less bright with a patina that builds up over time. Cleaning a cymbal will restore its original sound qualities and will not harm it in any way and makes your cymbal look new again. I have used a mothers mini ball  and blue magic  metal polish on my own cymbals with great results.