Wire's diameter is measured in "gauges." An example of a very heavy wire is 8g. "g" stands for gauge. An example of a very fine wire is 30g. The higher the number the finer the wire. It's typical to find the gauges in increments of 2, for example, 16g, 18g, 20g, 22g, and so on. Sometimes wire can be found in odd gauges, such as 19g or 21g, which I do use occasionally. Industrial wire is measured the same way.
I don't like to use finer than 20g wire (if silver) in the rosaries. That way I know it's strong. Most gemstone beads take 20g with no problem. Organic stones like coral and pearls usually won't take anything heavier than 22g, so I order fine wire in a "hard" temper for maximum sturdiness. Bronze wire is very strong. Likewise, I use 20g when the beads allow. In bronze, I never use anything other than half-hard and it has good natural strength in almost any gauge. That's one reason bronze is such a favorite with me.
Wire is offered in variable "tempers" or degrees of hardness or softness. Customary tempers are "hard," "half-hard," and "dead soft." Ordinarily, half-hard is typical for 20 to 21 gauge and heavier. Hardness is determined by how many times the wire is drawn through drawplates. The more times it's drawn, the harder the wire. Half-hard means it's been drawn half the number of times it takes to achieve "hard." Half-hard allows for flexibility so that the wire can be most conveniently worked by hand. I order hard wire in the finer gauges (coral and pearls) so that once assembled, the wire is a bit more rigid and won't "bend out" if tugged on. Each temper has its particular uses as I've already described a bit. Dead soft is often used in elaborate wirewrapping applications because it is so flexible and maleable, but half-hard wire may be easily wrapped in "rosary turns," which is the familiar loop under which the wire is coiled a few times.
"Fine Silver" is available in addition to "sterling" and "Argentium." One advantage to both fine silver and Argentium is that they can be soldered without additional solder wire or paste. It fuses to itself in other words. Sterling silver means it is 92.5% silver and 7.5% alloy, usually copper. (Oxidation of the copper in sterling is what causes the tarnish.) You'll often see "925" stamped on the back of sterling pieces and that indicates the sterling standard of 92.5% pure. "925" and "Sterling" hallmarks are commonly used by manufacturers in the U.S. Countries generally have their own hallmarks for purity markings. Fine silver is a 99.9% silver ratio. Argentium is sterling with the addition of germanium in place of some of the copper. As it retains its 92.5% purity, it remains "sterling."
From Wikipedia: Silver occurs naturally in its pure, free form (native silver), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a by-product of copper, gold, lead, and zinc refining. Silver has long been valued as a precious metal, and it is used to make ornaments, jewelry, high-value tableware, utensils (hence the term silverware), and currency coin.
