Why Does Sterling Silver Tarnish?

Tarnished silver pot

Sterling silver is a silver alloy containing 92.5 percent silver and 7.5 percent copper. Pure silver is too soft for functional objects, so metalworkers produce silver alloys; the most popular alloy for silver jewelry and dishware is sterling. Copper gives pure silver strength, but doesn't interfere with silver's malleability or color.

Silver tarnish build-up occurs when the outermost layer of silver reacts with sulfur or hydrogen sulfide in the surrounding air.

History of Sterling

The earliest use of the term sterling emerges from "esterlin," in a charter from the a French abbey in Préaux from 1085 or 1104.

Most scholars suggest that the term "sterling" derives from an Old English description of the new Norman penny, which had a small star on it. The word, if of English origin, presumably described some peculiar characteristic of the new Norman penny.

Chemistry

Silver is not very reactive chemically; at ordinary temperatures silver doesn't react with oxygen or water. As the silver's purity decreases, however, the risk of tarnish or corrosion increases. Other metals like copper, the usual alloy in sterling silver, may react with oxygen in the air. Table salt, or sodium chloride, frequently corrodes silver-copper alloys. Commonly, salt corrosion appears on silver salt shakers around the holes in the top.

Dining Silver

From 1840 until around 1940, many Americans and Europeans considered silver flatware a necessity for a properly set table. The high demand for silver forks, knives, spoons and other dining accessories propelled a large industry of silver flatware manufacturers.

The silver craze peaked from 1870 to 1920, where dinner courses went from three to 10, and some flatware settings contained more than 100 different types of silver pieces.

It's not surprising then, that many American inherit old silver table settings from parents and grandparents.

Tarnish

Tarnish is a chemical reaction between metal and non-metal compounds. Tarnish is usually some form of metal oxide, the result of oxidation (when metal is exposed to oxygen).

Silver tarnishes if it combines with sulfur; in chemistry terms this is silver sulfide. Silver sulfide is black, and darkens silver when a thin coating of silver sulfide appears on the outer layers of pure silver or silver alloys.

Tarnish Prevention and Removal

A thin coat of polish can stop tarnish from forming on reactive metals (like the copper in sterling silver).

You can remove tarnish with steel wool or sandpaper; however, most silversmiths recommend against abrasive techniques for fine silver pieces. There are a number of chemical tarnish removers available, all of which should be handled with care.

References

• Bluenile.com: Sterling Silver Education
• Oxford English Dictionary
• Charles L. Venable, "Silver in America, 1840--1940: A Century of Splendor," 1997
• Remove Tarnish From Silver