I need some help on a method to clean black spots from silver plate.
I've got a nice satin silver Buescher with close to 100% intact plating. But it has many tiny, tiny black spots that are not easy to clean away. First I thought it was small pittings in the silver, but when I put the horn under my microscope (being a microbiologist I usually solve most problems under a microscope) I see that the spots consist of a black crust on top of the silver. The silver under it is intact. The spots do not react to normal silver polish, silver polish containing ammonia or an acidic copper cleaner. The black ( maybe I see a green shade in the black ?) crust has a greater hardness than the silver and can be removed with a sharp object like a needle, but the resulting silver surface is not pretty after a needle job. From these observations I guess the spots are not made of silver sulphide.
Can anyone tell me what these tine black spots are and how I could clean them off the silver plate ?