An alloy made of zinc and copper, brass is durable and looks best when polished to a high shine. Whether your brass item is new or antique, tarnish steals its luster. One way you can remove tarnish and restore the brass piece's natural beauty is by dipping and cleaning it in either soapy water, ammonia or both. This technique works best for smaller brass items such as keys, door knockers and buttons.
Check to see if the item is true brass or just brass plated. Hold a magnet up to it; a magnet won't stick to real brass.
Fill a bowl or small bucket with warm water. Add a few drops of a mild dish-washing liquid and stir until bubbles form. Put on a pair of rubber or latex gloves so skin oils don't get on the brass item, which could cause more tarnishing.
Dip the small brass item into the soapy solution, completely submerging it. Allow the brass to sit in the water for 10 minutes or longer until the tarnish is gone. Use an old soft-bristled toothbrush to thoroughly clean any nooks and crannies.
Rinse off the item in clear water to remove any soapy residue. Dry the brass with a microfiber cloth, buffing it to a shine.
Dip-clean the brass piece in ammonia if the soap solution didn't remove all of the tarnish. Move to a well-ventilated area and put on protective gloves and goggles. Fill a bowl or small bucket with 1 part ammonia to 8 parts water.
Immerse the brass in the ammonia mixture, checking it frequently until all of the tarnish is gone.
Rinse the brass in soapy water to completely remove any ammonia, then dry and buff it with a microfiber cloth.