Silver tarnish is the result of the oxide on the silver surface reacting with hydrogen sulfide (H2S) in air. This leaves a black film of silver sulfide (Ag2S). Silver atoms are oxidized to form Ag+ ions.
When a thin coating of silver sulfide forms on the surface of silver, it darkens the silver.
The offending silver tarnish can be removed by either striping it from the surface or reversing the chemical reaction and turn silver sulfide back into silver.
