How to Protect Old Brass From Water

Test the brass with a magnet if you aren't sure it is pure brass. If it attracts the magnet, it is another metal coated with brass. In this case, polish it carefully and gently to avoid wearing through to the metal beneath.

Wash in warm, soapy water to remove dust, oil and any residue from previous treatment. Dry thoroughly with a towel, soft cloth or lint-free paper towel.

Polish the brass. Ideally, you should use a specialized brass and copper polish, which will protect the brass from tarnishing. For a cheaper alternative, you can get a great shine with lemon juice, Worcestershire sauce or ketchup. Apply with a soft cloth, then buff until it shines.

Use emery abrasive paper to remove any tough patches of corrosion. These are likely to be very dark -- almost black -- and can't be removed by normal polishing. Wet the paper and very carefully remove the corrosion with small, circular motions.

Treat the brass with lacquer. This will seal the surface, protecting it from water and air to prevent tarnishing.

For a cheaper alternative to lacquer, you can oil the brass. This won't last as long, but it will have the same effect for a while. Use a clean, soft cloth or a lint-free paper towel to apply a thin layer of oil, such as olive oil, all over the object. You can repeat this every few weeks for long-term protection.