What is Silver Tarnishing and What Causes It?

Tarnishing, also called toning, is an effect on the outermost layer of a metal that causes the metal to become discolored. Like iron rusts when exposed to oxygen, silver can tarnish when exposed to the air due to a reaction between silver and hydrogen sulfide in the air. Also, touching silver products with your hands may cause tarnishing over time due to the oils from your skin. 

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