Brass, copper, and other cuprous metals suffer from "bronze rot" that is
similar to ferrous rust and should be treated by a professional conservator. Once
removed from an archaeological context, the rot or corrosion can excellerate
with exposure to fluctuating environments. The worst thing to do is attempt to
clean it with Brasso or some other metal cleaner, as it will just damage the
metal. Conservators attempt to terminate corrosive processes and create a
patina that will stabilize the metals. Another serious issue can be salts that
crystallize once the metal is removed from its anaerobic moist environment, as the
crystals force the brittal metal to crack. Again, removal of salts is a
delicate matter that should be conducted by trained conservators. If you cant
afford a conservator, then leave the item alone and mark the container with a flag
that places high priority on conservation when funds do become available.

Ron May
Legacy 106, Inc.