Good ways to clean old brass include scrubbing it with salt and lemon, soaking it in vinegar or ammonia, and rubbing it with commercial brass cleaner. Lacquered brass must have the lacquer removed before cleaning, according to SF Gate.
Soaking old brass for an hour in either white vinegar or undiluted ammonia often cleans it effectively. This method leaves the brass shiny and tarnish-free. A lemon and salt scrub is a reliable alternative for brass that is too large to submerge in a bucket, and for objects that have non-brass parts, as these may be damaged by vinegar and ammonia.