Before You Begin: Is It Solid Brass or Brass-Plated?
The most important question before attempting to restore any brass fixture is whether it is solid brass or brass-plated. Solid brass can be polished, cleaned, and restored repeatedly without any risk of damage to the underlying material. Brass-plated fixtures — which have a thin layer of brass over a base metal such as zinc or steel — can be polished only gently, as aggressive polishing will wear through the plating and expose the base metal beneath.
To test whether a fixture is solid brass, hold a magnet to it. Solid brass is not magnetic; if the magnet sticks, the piece is brass-plated over a ferrous base metal. If the magnet does not stick, the piece is either solid brass or brass-plated over a non-ferrous base metal (such as zinc). In the latter case, look for areas of wear or damage — if you can see a different-coloured metal beneath the brass surface, it is plated.
Light Cleaning: Removing Water Spots and Surface Grime
For fixtures that have simply accumulated water spots and light surface grime, a gentle cleaning is all that is needed. Mix a small amount of mild dish soap with warm water, apply with a soft cloth, wipe gently, rinse thoroughly, and dry immediately. This will remove surface deposits without disturbing the patina.
For slightly more stubborn water spots, a paste of equal parts flour, salt, and white vinegar applied for ten minutes before rinsing will dissolve the mineral deposits without damaging the brass. Rinse very thoroughly after using this method, as any residual acid can continue to react with the metal.
Deep Restoration: Returning to the Original Bright Finish
If you want to restore a heavily tarnished piece to something close to its original bright finish, you will need a commercial brass polish. Products such as Brasso, Wright's Brass Polish, or Bar Keepers Friend are all effective. Apply a small amount to a soft cloth, rub in circular motions, and work in sections. The polish will turn dark as it picks up the tarnish — this is normal and indicates that it is working.
After polishing, rinse the piece thoroughly with warm water to remove all traces of the polish, then dry immediately and completely. Any residual polish left on the surface will continue to react with the metal and may create uneven discolouration.
Dealing with Verdigris
Verdigris — the green patina that forms on brass in humid environments — is copper carbonate, and it is more resistant to removal than standard tarnish. For light verdigris, the flour-salt-vinegar paste described above will usually be sufficient. For heavy verdigris, a commercial brass cleaner or a diluted solution of citric acid (available from homebrew suppliers) will be more effective.
After removing verdigris, dry the piece thoroughly and consider applying a thin coat of microcrystalline wax to protect the surface and slow the recurrence of the green patina.
After Restoration: Protecting the Surface
Once you have restored a brass fixture to the finish you want, you have two options for protecting it going forward. You can leave it unlacquered and allow it to develop a new patina naturally — which will happen more slowly now that the surface is clean and bright. Or you can apply a thin coat of microcrystalline wax (Renaissance Wax is the standard recommendation) to slow the oxidation process and maintain the bright finish for longer.
Do not apply lacquer to a fixture that will be used in a wet environment. Lacquer is not waterproof, and in a bathroom or kitchen it will eventually fail, leaving an uneven, peeling surface that is more difficult to deal with than natural patina.