When our fingertips (and others) touch the cymbal surface, acid transmitted through fingertips interacts with the alloys. They are amino acids to be all-scientific on you, and they can source approximately 100 times the concentration of amino acid found in a New Zealand fossil shell. That’s a lot of acid, dude, but the molecule also is the cleaning solution to your problem. Cymbals can easily tarnish from the dust produced by human skin, airborne grime emitted from nearby appliances such as boilers, and even wooden chafe from your stick strikes. There are a thousand ways to make cymbals dirty, but thankfully only a few methods actually work to get most of that shine back.
Most drum and cymbal manufacturers sell relatively mild and effective acid-based cleaners, and there are a few specialty products on the market that contain even stronger ingredients. “Groove Juice” is a hot one right now, for example. Most of these cleaners will over time take your logos off of your cymbals, however. So unless you want to eventually remove your logos, then you must clean around them or wash that area immediately if it comes into contact with your chosen cleaner.