Tarnish

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Tarnish is a layer of corrosion that develops over copper, brass, silver, aluminum as well as a degree of semi-reactive metals as they undergo oxidation. It is analogous to rust, but with a slower rate of occurrence. It is mainly caused by chemicals in the air such as sulfur. It appears as a grey or black film over the metal.

[edit] Prevention

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In objects which are primarily for display rather than use, the tarnishing process can be prevented in the long term by tinning, a process by which the reactive substance is coated in a non-reactive substance, such as tin or wax, and thus protected from oxygen.^{[citation needed]}

For more frequently used items such as silverware, tarnish is easily prevented by constant use and washing with a mild dish soap.^{[citation needed]}

[edit] Removal

"This kitchen version of electrostripping is safe and easy. It's especially useful for removing tarnish from flatware and holloware. In a pot lined with aluminum foil, mix a diluted solution of equal parts of baking soda salt, and liquid soap. A quarter cup of each to a gallon of water is a typical mixture. Set the sterling in the pot; bring the mix to a simmer and allow it to stand for 10-20 minutes as the oxides are transferred to the aluminum, which you'll see is darkened. Throw that away and wash the silver before using it".^[1]

Another way to treat tarnish is to put a drop of water and some fluoride toothpaste on a tissue and rub it on the affected metal.^{[citation needed]}