Why does silver tarnished?
Silver is a shiny, white metal. But unless polished on occasion, objects made of silver may soon lose their brightness and become coated with a dull film.
When silver turns dark, we say it is tarnished. Silver tarnishes for almost the same reason that iron gets rusty. In fact, the word “tarnish” is used for rust formed on copper and other metals other than iron.
Tarnish is a form of corrosion caused by a chemical change when oxygen in the air combines or joins with the silver metal. It forms a dark-colored film called silver oxide. The tarnish helps protect the silver against further corrosion.
Soap and water will not remove it. To make silver look shiny again, we have to use silver polish to remove the tarnish.
The silver polish changes the dark tarnish back to two separate elements, silver and oxygen—another chemical change. Eggs and some other foods contain chemicals that can also cause silver to tarnish quickly. – Dick Rogers