The following procedure is from a pamphlet printed by Baldwin Hardware Corporation. It is for renewing your solid brass, lacquered products only. This procedure should not be used for brass plated items. If you do not know if your item is solid brass and lacquered, we suggest you check your local yellow pages for a metal refinisher who can tell you.
Step 1: Remove the old coating
Remove any protective acrylic coating or dirt remaining on the hardware with an extra fine (0000 grade) steel wool and an environmentally safe paint stripper. To protect fine door finishes, it is advisable to remove hardware to prevent damage to the surface.
Step 2: Polish the brass
With the coating removed, polish the brass with fine-quality brass polish (see below for options). This should completely renew your hardware to its original shine and luster.
Step 3: Protect your hardware
Finally, to protect the hardware from the elements, either seal the surface with a high-quality, non-abrasive, polymer-based car wax, or, if you prefer, a solvent cleaning and a coating of good exterior polyurethane sealer. Please note that with furniture coatings of polyurethane, hardware should be removed and cleaned as in step 1. Once stripped, polished and resealed, your brass hardware will have a glossy, golden glow which will be preserved for several months with a wax coating. It may take many repeated applications to build up the protective coating required to maintain it for long periods.