Sterling Silver
Sterling silver is an alloy of silver containing 92.5% pure silver and 7.5% other metals, usually copper. The minimum amount of silver to be labeled Sterling 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 while at the same time preserving the malleability or ductility of the silver and a high precious metal content. So, in other words, it’s soft enough to create items such as trays, tea sets and cutlery, yet it is strong enough to maintain it’s shape without breaking or fracturing.
In the US you will see Sterling Silver marked with 925, .925 or Sterling. These stamps are called Hallmarks and depending on where the Sterling comes from you will see different stamps, such as the crown that Sheffield Sterling Silver from England uses.
The downfall of Sterling Silver is that it tarnishes and requires cleaning frequently and this is mainly due to the copper content of the piece. There are new Sterling Silvers emerging on the market that have changed the other metals to those that maintain the integrity of the Sterling, yet create a virtually tarnish resistant finish.
Thai Silver
Fine silver is 99.9% silver or better. This grade of silver is used to make bullion bars for international commodities trading. In the modern world Fine Silver is understood to be too soft for general use. Thai Silver falls in between Sterling Silver and Fine Silver. It is strong enough to be crafted into smaller items which makes it perfect for jewelry-making. Thai silver also has the benefit of not tarnishing the way that Sterling does because there is no copper in Thai Silver. Most of the silver comes from the Hill Tribes.
eBay info on Thai Silver http://reviews.ebay.com/The-Beauty-of-Thai-Silver_W0QQugidZ10000000001815688?ssPageName=BUYGD:CAT:-1:LISTINGS:6
