Silver tarnishes due to a reaction with sulfur in the air. Moisture and sunlight can also cause tarnish.
The air is filled with many different compound gases, including several that contain sulfur. The sulfur reacts with the silver to create silver sulfide, which appears as a dark coating on the silver. Moisture and humidity can promote these reactions, which is why silver tarnishes quicker when the air is damp or humid.
UV rays in sunlight can also cause tarnish. This happens because the silver absorbs the radiation and produces tiny particles, creating a tarnished look.
Climate control and proper storage can help reduce tarnishing. Owners should keep silver jewelry and objects stored away from sunlight in cool, dry places. They should also take measures to reduce humidity levels inside their homes.
Tarnished silver is often easy to fix. Light tarnishing often comes off after polishing the object with a cloth and an abrasive substance, as this rubs the silver sulfide from the surface of the object. However, seriously tarnished objects are also usually fixable. Owners can simply reverse the chemical reaction that caused the tarnish using baking soda and an aluminum pan. They can place tarnished objects in an aluminum pan, sprinkle up to one cup of baking soda over the silver, cover the silver with warm water and remove the objects when the silver is clean. The baking soda causes the sulfur to transfer to the aluminum, which removes the tarnish from the silver.