As brass oxidizes, it forms a dull tarnish to slow down the corrosion process, and while this is a natural defense mechanism for the alloy, it's not a look many homeowners embrace. When this occurs, you have to strip the brass of its already-eroded finish to restore its natural shine. As an alternative to chemical strippers like paint thinner and acetone, ammonia lets you skip past the scraping, allowing you to give your brass a simple soak. As such, this method only works for brass that you can fit in a bucket or household container.
Give the brass a thorough wipe-down with a soft cloth dampened in soapy water, and get into any crevices with a soft-bristled toothbrush. Once you've freed the brass of any grime or debris, do a pass with a plain damp cloth before allowing it to dry completely.
Don a face mask and rubber cleaning gloves. In a well-ventilated area, combine ammonia and hot water in your container. Combine the mixture at a ratio of one part ammonia for every two parts of hot water.
Completely submerge the brass in the ammonia solution. Keep an eye on the brass; it should only take a few minutes for the tarnished finish to fade. When it does, remove the fixture from the solution with your gloved hands.
Brush the entire surface of the brass with a soft-bristled toothbrush to remove any loose residue or remaining finish. Rinse the brass thoroughly under warm water, then pat it dry with a clean cloth and allow it to air-dry completely.