You can reduce the silver sulphide back to silver metal using
a bit of aluminum foil and some sodium carbonate solution.
Works great on badly tarnished silverware, and doesn't leave
big copper splodges the way polish does. (Polish contains abrasive.)

I'll remember that one.
?-)

The poster is correct. I have a kit with a large aluminum plate. You put it
and the silverware in a hot washing soda solution, and the tarnish goes
away.