I work with mainly tarnish resistant brass. Inevitably over time brass can lose its shine and become dull as oxygen, water, oils from your skin and other elements cause this to naturally happen (oxidation) 

So you can shine it up with a pre polishing cloth which I offer to purchase on my shop and or you can also use lemon, a little warm water and baking soda to create a thick paste, apply the scrub to your brass & let it sit for 5 minutes, then use a very damp rag to wipe off! I suggest polishing your jewelry after every wear since it is being exposed to your natural oils, lotions or perfumes it important to give it a little shine up to remove anything that may be left on it. Store your jewelry by hanging up and or laying flat in the box it came in. Avoid mixing metals and ALWAYS remove pieces when showering/swimming or washing your hands, doing so will allow your pieces to last longer and be wearable! Take care of your pieces friends & if you have any questions please feel free to email me.