Sterling silver contains at least 92.5% silver. Pure silver is very soft and is usually alloyed to give pieces made from it strength and durability. The other 7.5% in sterling silver is often copper; however, several types of sterling alloys are commercially available.
Pure silver is not a particularly reactive metal; that is, it does not combine with oxygen or water at ordinary temperatures, but copper is. When sterling silver combines with ordinary air the sulfer present in the air will combine with the copper in the sterling silver to form a corrosion called tarnish. This black film is actually a silver oxide (Ag2S) and can be removed in several ways.
Argentium Sterling Silver™
An alloy of silver containing at least 92.5% silver and some percentage of germanium replacing the traditional addition of copper. It has a melting temperature of about 60 degrees Fahrenheit less than traditional sterling alloys.
The addition of germanium (a chemical element, atomic number 32) gives Argentium Sterling Silver many advantages over traditional alloys. The germanium in Argentium Sterling Silver oxidises preferentially to the copper and silver to form a transparent germanium oxide surface layer. The germanium oxide forms before the copper in the alloy can combine with sulfer in the air and prevents the copper from creating tarnish. Argentium Sterling Silver stays non-tarnished because germanium atoms continually migrate to the surface of the alloy and replenish the germanium oxide layer. This is what gives Argentium Sterling Silver its non-tarnish quality. Argentium Sterling Silver has increased ductility and increased thermal resistance as well as other benefits.
Argentium Sterling Silver is a proprietary material and both patented and trademarked by the Argentium Sterling Company, UK.
I am moving to working in Argentium Sterling Silver as I enjoy the working qualities of this material more than I do traditional sterling alloys. While it is slightly more expensive than traditional alloys the decrease in maintenance is more than worth the cost.
Gold-filled or Gold Fill
A material made from brass (a copper-zinc alloy) that has a layer of gold, usually 14kt gold, heat and pressure bonded (laminated) to the brass.
This material is used in making jewelry where the look of gold is desired without the corresponding cost. It differs from gold plate in that the layer of gold used in gold fill is an actual percentage weight of the material rather than a coating measured in microns (less than .1% by weight). Because gold-fill uses significantly more gold than plating the items made from it have much better wear and durability characteristics.
Gold-fill terminology expresses the amount and karat of gold present by volume. The most common formulations of gold-fill are 12/20 and 14/20. The #/20 notation refers to the ratio of karat gold to brass core by weight, which is 5% (5% of 100% can be expressed as 1/20th) and the # refers to the karat of gold used in the gold-fill. For example, 14/20 gold-fill is 14kt gold over brass and 5% of the weight of the gold-fill is 14kt gold. The other 95% is brass.
I use 14/20 gold-fill work but when I solder it I use 14kt gold solder for better color matching.
An alloy of gold containing at least 58.5% gold. Pure gold, like pure silver, is very soft and is usually alloyed or mixed with other metals to give it strength and durability, as well as to lower the cost.
The karat system is used to express the purity of gold in an alloy where pure gold (99.99% fine) is expressed at 24 kt gold. 14kt gold is 14/24 gold, that is, 14 parts (58.5%) of the alloy are gold and 10 parts (41.5%) are some other material.
Gold is alloyed with many different elements. The alloying material will determine color and working characteristics of the material. Generally, silver is added color gold green, copper is added to color gold red, iron is added to color gold purple or blue (very uncommon) and adding nickle or palladium will color gold "white" or silvery. Many white gold alloys are electroplated with rhodium for added shine. Gold alloys are frequently referred to by both karat and color, i.e. 14ky, 14kw. Melting temperatures of gold alloys are dependent on the mixure.