Sterling silver
Silver with 7.5 per cent copper, because pure silver is too soft to make anything from — and the copper is what makes it tarnish.
Sterling is 92.5 per cent silver and 7.5 per cent copper, and the proportion has been fixed by statute in England since the twelfth century. Pure silver is too soft to hold a form: a fine silver spoon bends in use and a fine silver ring deforms on a finger.
The copper does two things. It hardens the alloy substantially, and it makes it tarnish — the black film on old silver is silver sulfide, formed from traces of hydrogen sulfide in air, and the copper accelerates it. It also causes firescale, a dark copper oxide layer that forms below the surface during annealing and is the silversmith's standing nuisance, because it appears when the piece is polished and has to be removed by cutting away metal.
The hallmarking system exists because none of this is visible. Silver content cannot be judged by eye, and the assay office marks are among the oldest consumer protection instruments still in operation.
Processing
Cast, rolled, drawn, raised and forged. It work-hardens as it is formed and must be annealed repeatedly — raising a bowl from flat sheet may take a dozen cycles of hammering and annealing.
Soldered with silver solders of decreasing melting point, so that successive joints can be made without unmaking the earlier ones. Argentium and other modern sterling alloys substitute germanium for some of the copper, which largely eliminates firescale and slows tarnishing, at a price.
Uses
Tableware, jewellery, ecclesiastical and ceremonial objects, musical instruments — flute bodies and some brass instrument components — and historically coinage, which is where the standard comes from.
Silver's other industrial uses are overwhelmingly for the pure metal rather than the alloy: electrical contacts, brazing alloys, photovoltaic paste and antimicrobial applications all want the silver rather than the hardness.
History
The standard is documented in England from the twelfth century, and hallmarking from 1300 — the leopard's head mark of the London assay office is one of the oldest continuously used quality marks anywhere.
The word's origin is disputed and the most common explanation, from the Old English for a small star on early Norman pennies, is contested; another derives it from the Easterlings, north German traders whose coinage was trusted for its consistency. Both are plausible and neither is settled.
How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.
How this connects
Where a connection has been confirmed by an outside reference, that reference is named beside it.
contains
is used as
- Tableware and vessels — application · and the hallmarking system exists because the silver content cannot be judged by eye
is an alternative to
- Cupronickel — alloy · in tableware, where cupronickel is the cheap substitute that looks similar and was sold as such
is produced by
- Alloying and melting — process · seven and a half per cent copper into silver, which is the standard because pure silver is too soft to hold a shape
Sources
- Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
- Material WorldOur own writing