Ultimately my experience with the vinegar solution was deceiving.
As I wrote to another reader, I used one gallon of pure vinegar and
one coffee cup of salt.  I did not test the naphtha.

  http://www.ganoksin.com/orchid/archive/200911/msg00033.htm 
  http://chemistry.about.com/cs/howtos/ht/brasscleaner.htm 

It is the first time that I used that recipe.  At first it gives a
fantastic result, but the tarnish comes back very rapidly (2 days).
I don't suggest that you use it.

The best product that I have used up to now is Sparex [sodium
bisulphite].  It is used by jewelers.  You mix a small quantity of it
in a pint of hot or warm water and it makes the brass finish nice.

Thanks for reading.

Robert Patoine

 [ MSDS information about Sparex Pickling Compound is at
 [ http://www.esslinger.com/learning_center/msds/45.127.pdf  -- Robbie