Tarnishing, darkening is natural for metals. For some, this contributes to being lived in, and is a romantic quality. However, you may prefer the original condition of your jewelry, and there are ways to maintain this condition or achieve it.
There are many factors to influence the condition of your favorite jewelry. Keep your jewelry dry, remove before bathing, washing or doing physical activities such as gardening, sports and before going to bed. Avoid contact with perfumes, moisturizers, apply these products a couple minutes before wearing your jewelry.
Always store each of your jewelry separately. When storing your silver jewelry, use an airtight plastic bag and if you can, put in a piece of chalk or a silica gel (the little packets in new shoes) - these will help prevent tarnish while you are not wearing your jewelry.
METAL SPECIFIC INSTRUCTIONS:
It is natural for your silver jewelry to tarnish when it comes into contact with oxygen or sulfur. The best way to clean is with a jewelry polishing cloth. If you prefer to wash with soap and warm water, make sure to use a very soft toothbrush to avoid scratching. Do not use tissue paper or paper towels to clean metal as they can again cause scratching. There is also an easy way to overcome this: Wear your silver jewelry often! The oils in your skin will help prevent tarnish, this scenario varies depending on your own body chemistry.
Brass may darken with wear, also turn your skin slightly green depending on body chemistry. If you don't like the dark patina, try to avoid getting your brass jewelry wet. A commercial brass cleaner, like “JAX” (there is also non-allergic JAX versions available) will restore your piece to its original shine. Make sure to read to instructions carefully before applying, and apply with a very soft brush. If this is unavailable, use a soft toothbrush or soft damp cloth and toothpaste to polish, dry with a soft cloth.