Silver grades
The number stamped on silver is its fineness in parts per thousand.
| Grade | Silver content | Stamp |
|---|---|---|
| Fine silver | 99.9% | 999 |
| Britannia silver | 95.8% | 958 |
| Sterling silver | 92.5% | 925 |
| Coin silver (US) | 90% | 900 |
In the US, the FTC’s jewelry guides say “sterling” should only be used for silver that’s at least 925/1,000 pure. The UK hallmarks 999, 958, 925 and 800 silver.
Fine silver is very soft and dents easily, so Cooksongold suggests keeping it for earrings and pendants that won’t get knocked. Sterling is alloyed with 7.5% copper for strength. Britannia silver has less copper and is slightly softer than sterling.
Silver in a piece
Multiply the weight by 0.925. A 20 g sterling bracelet contains 20 × 0.925 = 18.5 g of silver. Silver is weighed in grams or troy ounces.
Tarnish
The Canadian Conservation Institute explains that tarnish is silver sulfide, formed when silver reacts with sulfur gases in the air, such as hydrogen sulfide. Sterling tarnishes faster than pure silver because of the copper in it.