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13 January 2010

Archives November 2008 : Question & Answer

Q :
What is the difference between soft, half hard, and full hard wire?

All metals have a property called hardness. Hardness is the characteristic of the metal that resists bending. Soft metals are pliable and easy to bend. Hard metals are stiff and hard to bend. The hardness of metals can be changed by heat treating the metal in a process called annealing or by simply bending the wire in a process called work hardening.

Wire, like all metals, will have this same hardness property. Historically, numbers (0, 1, 2, 3, or 4) were used as labels to define the hardness of the wire. The numbers correlated to the number of times that the wire was pulled through the draw plate. The wire becomes harder or stiffer after each time it is drawn through the drawplate. A hardness of 0 meant that the wire was drawn only one time and was as soft and pliable as possible. A hardness of 4 meant that the wire was drawn five or more times and the wire was as stiff and hard as possible.

Currently the designations 0, 1, 2, 3, and 4 no longer correlate to the number of times that the wire was drawn because the hardness of the wire can be changed by heat treating the wire. Practically, most jewelry wire is sold now as either dead soft, half-hard, or hard, with dead soft being wire manufactured with a hardness of 0, half-hard being wire manufactured with a hardness of 2, and fully hardened wire being wire with a hardness of 4.

Dead soft wire can be easily bent and is excellent for making rounded shapes including a spiral. The disadvantage of using soft wire is that the finished piece can be bent out of shape if not properly handled. Soft metal is best when soldering, as the heat from soldering process will anneal the metal and will soften the temper.

Half-hard wire is slightly stiffer than dead soft wire. It is excellent for making tight, angular bends, for making loops in wire, and for wrapping wire around itself. Finished pieces made with half-hard wire are often more permanent than pieces made with soft wire. Half-hard wire is good for handmade ear wires, wire wrapped jewelry and wire sculpture.

Hard wire is very stiff and tends to spring back after being bent. This can make it harder to work with when using a jig. Although the wire components made out of hard wire are difficult to make, they will be very permanent. Hard wire is good for making springs and pins.

As mentioned above, the hardness of the metal can be changed. Many times the various processes of jewelry making will harden or soften the metal. Hardening the metal can be accomplished by bending, hammering, coiling, twisting, tumbling, or by any other manipulations to the metal. This process is called work hardening. Work hardening is an actual physical change to the molecular structure of the metal. The molecules move closer and closer together becoming more and more brittle, eventually breaking the metal.

Heat treating or annealing the metal will soften the temper of the metal and prevent the metal from breaking, ultimately relaxing the molecules. During the annealing process, the metal is uniformly heated to a temperature that is lower than the melting point or soldering temperature. Therefore, soldering will anneal the metal as well.

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