Jewelry wire comes in many different metals, ranges of hardness, shapes, gauges and finishes. The hardness of the wire refers to the malleability. Hardness also differs by material. Sterling is harder than copper. Brass and bronze tend to be stiffer than both copper and sterling. When you’re working with very fine gauges, hardness is a bit irrelevant, since fine gauge wires are so thin and pliable.
Gauges: Almost all jewelry wire in the US is sold in sizes defined by the American Wire Gauge. For jewelry making, you will usually use gauges from 12 to 26. (See Wire Size for Jewelry.) As the gauge of the wire increases, the size of the wire decreases. As an example 16 gauge wire is much larger than 22 gauge wire. As the wire gets larger, or the gauge gets smaller, the wire becomes harder to bend.
If you work with thicker gauges, you want to choose the hardness most appropriate for the work you’re doing. For instance, if you want to make ear wires, you know they should have some stiffness and spring to them. But if you’re coiling wire, you want that wire to be soft enough to easily wrap around whatever you’re using as a mandrel.
Hardness: Wire usually comes in three levels of hardness, which affects the wire’s malleability as well as its ability to hold its shape.
Full hard: fully tempered, very hard and stiff. There is rarely a call for full hard in jewelry making.
Half hard: softer than full hard, but still holds its shape well. Good for ear wires or hooks.
Dead soft: very soft, no spring, very pliable. Best for bending, coiling, hammering, and manipulating the wire a lot. Can also be shaped with your fingers.
Inexpensive wire, like copper, brass, or Artistic Wire, is generally made soft. Other wires like sterling silver, Argentium, gold, or gold-filled wire are commonly manufactured in one of the three above mentioned hardness.
Work hardening your wire: All metal becomes stiffer when you work with it. That’s called work hardening. Any sort of manipulation of the wire changes its molecular structure, causing it to become harder and more brittle. Most of us have experience in breaking a wire coat hanger by bending it back and forth. With the coat hanger, we were changing the hardness of the wire by “work hardening” it. Each bend increased the hardness of the wire until we saw one of the drawbacks of very hard wire, it becomes brittle and breaks. To make our jewelry components permanent, we frequently want to increase the hardness of the wire. This can happen naturally as part of manipulating the wire into its shape.
The only way you can return the wire to its softer state is to heat it, which you can do if you have a torch or a kiln. You can always harden soft wire by hammering, either with a metal hammer to flatten and texture, or with a rawhide mallet, to maintain the roundness but temper, or harden the metal.
Shapes: The most common wire shapes are round, half-round, square and triangle. There are also patterned and twisted wires.