At the end of the last guide I wrote that a good piece should carry a clear purity mark, such as 925. Customers often ask me what those three digits really promise. The short answer: of every thousand parts, 925 are pure silver. The longer answer is a story of more than eight hundred years, and it ends with a question worth asking any jeweller: what are the other 75 parts?
Why not use pure silver?
Pure silver, marked 999, is beautiful but soft. A ring made of it bends, scratches and loses its shape in daily wear. A small amount of another metal makes silver hard enough to hold a design, a sharp edge and a stone. The art is to add enough for strength and no more, so the metal stays white and stays silver.
Where does the 925 standard come from?
From medieval English money. English silver pennies were made to this fineness very early, and a piece of silver from the reign of Henry II (1154-1189) later served as the reference sample for testing the coinage, in the Trial of the Pyx, until 1843.
The recipe was simple: in every 240 parts, 222 parts silver and 18 parts copper. That is exactly 925 in a thousand.
Where the word "sterling" comes from, nobody knows for certain. One theory points to the "Easterlings", merchants from the Baltic towns of northern Germany whose money was trusted because it was never debased. Another links it to early Norman pennies stamped with a small star. Historians still argue, and I am happy to leave both stories on the table.
In 1300 Edward I made the standard law for silversmiths, not only for coins. Wardens of the London goldsmiths went from shop to shop, tested the silver and struck every approved piece with a leopard's head. This is where the hallmark begins, and the word itself comes from Goldsmiths' Hall in London.
Has the standard ever changed?
Yes, once. From 1697 to 1720 English silversmiths were required to work in a higher standard, Britannia silver (958), because people were melting sterling coins to make tableware. The softer metal did not please the trade, and sterling returned in 1720. Britannia remains an optional standard to this day. British coins themselves stayed sterling until 1920, when their silver content was halved.
In America there was no national standard at first. Tiffany & Co. adopted the English 925 standard in 1851, and it later became the American standard as well. Today 925 is the most widely accepted silver standard in the world.
What was the other 7.5% in the beginning?
Copper. For centuries sterling meant silver and copper, nothing else. Copper gives hardness and, in that small proportion, keeps the colour white. It has two weaknesses. When the metal is heated during making, copper oxidises and can leave a grey shadow just under the surface, called firescale. And it makes the silver tarnish faster.
What is used today?
Copper is still the main partner, but modern alloys share the 7.5% with small amounts of other elements:
- Zinc and silicon are the most common additions in casting alloys. They protect the molten metal from oxygen, so castings come out cleaner, with less firescale and fewer pores.
- Germanium is the most important newcomer. Peter Johns began researching it at Middlesex University in London in 1990, and the result is known today as Argentium silver. Germanium forms a thin, invisible protective layer, so the silver tarnishes much more slowly. Argentium grades contain 93.5%, 94% or 96% silver, more than sterling.
- Tin, indium and boron appear in small amounts in some alloys, to refine the grain and reduce firescale.
The 925 mark guarantees the silver. It does not tell you which of these makes up the rest.
Why does silver darken faster on some people?
Customers often tell me that their ring darkens faster than a friend's, and they are right. Many people explain it as "acidic" or "alkaline" skin, but healthy skin is always mildly acidic, so that is not the real reason. What matters is what reaches the metal: the salt in your sweat, which varies a great deal from person to person, sulphur from foods such as eggs, garlic and onions or from some medicines, and everyday products like hand cream, perfume, soap and pool chlorine. Rings take the most of this, because they sit against the skin all day and go through every hand wash. Most of what we know here comes from jewellers' experience rather than formal studies, so my advice is simple: take your ring off for cleaning and swimming, and wipe it after wearing. If your silver has already darkened, our How to Clean page shows two easy methods with everyday items.
Can sterling silver cause an allergy?
For most people, no. True allergy to silver is very rare. When someone tells me "I am allergic to silver", the cause is almost always nickel, the most common metal allergen in jewellery. Nickel has no place in a proper sterling alloy, but it can appear in cheap pieces as a hardener, or in a base metal under a silver plating.
And the new alloys? Zinc, silicon, germanium and tin are not known as common skin allergens, and Argentium is described by its makers as hypoallergenic. Copper allergy exists but is uncommon. Copper is more often the reason for a green or dark mark on the skin, which is a reaction with sweat, not an allergy.
The real risk is the false 925. A Danish consumer test of jewellery bought from large online platforms found pieces stamped "925 sterling silver" that were made almost entirely of cadmium. A stamp is only as honest as the person who struck it.
In the European Union the limits are strict. Jewellery in prolonged contact with the skin may release no more than 0.5 micrograms of nickel per square centimetre per week, 0.2 for piercing posts, and cadmium is limited to 0.01%.
What should a sensitive buyer ask?
- Is it marked 925, and by whom? A maker's mark or an assay office mark next to the number tells you someone stands behind it.
- What is in the other 7.5%? Ask plainly whether the alloy is nickel-free.
- Is it plated? Rhodium plating hides the alloy beneath, but it wears through in time, especially on rings.
- Who made it? A maker who knows the alloy can answer these questions. If the seller cannot answer, that is an answer too.
- Does your skin react? Take the piece off and see a dermatologist. A patch test shows which metal is the cause.
Quick answers
Is "silver plated" the same as sterling?
No. Silver plate is a very thin layer of silver over another metal. Sterling is silver all the way through.
Does "nickel silver" or "German silver" contain silver?
No. It is a mixture of copper, nickel and zinc, and nickel makes it a poor choice for sensitive skin.
Is a higher number always better?
A higher number means more silver, and also softer metal. For a ring worn every day, 925 is a sound balance between purity and strength.
Murat Bakış, Founder & Designer, Mu Design Jewelry · Ruse, November 2026
Sources: The Goldsmiths' Company and Assay Office London, history of hallmarking and the statute of 1300; Encyclopaedia Britannica, "sterling"; Wikipedia, "Sterling silver" and "Britannia silver"; Tiffany & Co., "A Legacy of Sterling Silver"; Middlesex University, REF impact case study on Argentium silver; Ganoksin, "De-oxidized Sterling Silver Alloys"; J. Fischer-Buehner et al., "A New 925 Silver Alloy with Increased Tarnish Resistance" (Assay Office London); Ganoksin Orchid, jewellers' discussions on body chemistry and tarnish; DermNet, "Jewellery allergy"; EAACI patient information on contact allergy; Forbrugerrådet Tænk, chemistry test of jewellery from online platforms (May 2025); EU REACH Regulation, Annex XVII, entry 27 (nickel) and entry 23 (cadmium), and Assay Office Sheffield, nickel testing.
