Clean brass is highly reflective and used to make all sorts of items. Whether you have brass door knobs or a shelf full of decorative brass trinkets, proper care is needed to maintain the brass item's shine. Over time or with improper cleaning, brass molecules can oxidise. This creates the discoloured, tarnished appearance you wish to eliminate. Fortunately, tarnished brass can be cleaned fairly easily with the aid of acidic substances and a bit of polishing.
Saturate a clean cloth in vinegar and apply it liberally to your brass item. If your item is small, you can also pour vinegar into a small container and allow the item to soak for several minutes.
Remove the item from the vinegar bath (if applicable) and use a fine grade steel wool pad to polish your item. Move in small circles, and concentrate on areas that are heavily tarnished. If your item is brass plated rather then solid brass, use a soft cloth to polish instead of the steel wool.
Rinse the brass item with water to remove all remaining traces of vinegar. Extended contact with vinegar can sometimes discolour brass items. Dry thoroughly with a towel.
Mix together 2 tbsp of lemon juice and enough baking soda to create a thick paste.
Apply the paste to a clean cloth and rub it liberally over the surface of the tarnished brass.
Rinse the item with water. Dry completely with a towel.
Cut a lemon in half and sprinkle the surface of the exposed lemon with salt.
Rub the salted lemon over the brass item, scrubbing the discoloured areas. The salt acts as an abrasive, so use care when scrubbing brass-plated items.
Rinse the item with water, then dry the surface completely with a towel.
Apply a small amount of baby oil to a cloth and polish your brass item once it has dried.