Firstly the flatter the surface the more difficult it is to polish.
As the surface presented to the mop is large as opposed to, say, a
3mm round wire ring shank.
Secondly you are using far too soft polishes and mops. Try buying
some bristle mops for the first polish with a tripoli polish followed
by a hard yellow mop with tripoli then an inter- mediate cotton mop
to remove any polish before using soft mops and rouge etc. At all of
polishing stages attack the surface from different angles and press
The grey is firestain, copper oxide, prevention can be aided using
fluxes and longer immersion in the acid.
Polishing is the worst part of jewellery making but very important
from the customers point of view.