Sterling Silver
Sterling silver is an alloy of silver containing 92.5% pure silver and 7.5% other metals, usually copper. The minimum millesimal fineness is 925.
Fine silver (99.9% pure) is generally too soft for producing large functional objects, and in Sterling the silver is usually alloyed with copper to give strength whilst preserving the ductility of the silver and a high precious metal content. Other metals can replace the copper, a recent development being the use of germanium to reduce firescale in manufacturing and to give a high resistance to tarnish. However, the germanium containing alloy has not been widely taken up due to questions over the effectiveness of its tarnish resistance and the difficulty of working with the alloy.
The most recent development is the production of a entirely new sterling silver alloy which has the highest resistance to tarnishing of any sterling alloy yet produced. This has been developed by Sheffield Hallam University [1] and Carrs of Sheffield [2], a leading silverware manufacturer. In this new alloy, known as Carrs Lustre Silver, the copper has been replaced by up to 10 other elements designed to give tarnish resistance, eliminate firescale and have mechanical properties close to or even better than standard sterling silver.
Origin of the term
The term "Sterling Silver", in reference to the .925 grade of silver, emerged in England by the 13th century.
The terms "sterling" and "pound sterling", seem to have acquired their meaning over a period of time, and from several convergent sources. The first mention is that of "sterilensis" in 1078, and by the thirteenth century (by the 1200's) the term sterling had appeared. "Sterling" comes from the Old French esterlin.
Mexican silver is also purer than sterling, usually 95% Silver and 5% Copper. Mexico is the only country currently using silver in its circulating coinage, but these coins are not minted from 95% "Mexican" Silver.
Coin silver is 90% silver and 10% copper as dictated by United States FTC guidelines
As the purity of the silver decreases, the problem of corrosion or tarnishing increases.
Chemically, silver is not very reactive — it does not react with oxygen or water at ordinary temperatures, so does not easily form a silver oxide. However, the other metal in the alloy, usually copper, may react with oxygen in the air.
