Hardening Wire For Strength
Unless you buy full-hard or memory wire, you will probably need to work-harden it to make it keep its shape. Always harden wire AFTER you are done working on a component or section. While you can reshape after hardening, it’s generally difficult to do and may cause breakage of your piece. It’s important to harden any component that will have any degree of stress when wearing – chain links, jump rings, clasps – and you may chose to harden a piece of your work simply to change the style or appearance!
There are several methods to harden wire work:
Hammering. On the positive side, this method is easy and controllable. It does, however, change the appearance of your wire and if you are not careful, can distort carefully created shapes. Use an anvil or striking block and a hammer. The striking surfaces must be unmarred and used ONLY for wire work. Any dings, dents or scratches in your anvil, block or hammer will show up on your wire.
Place the wire to be hardened on the anvil or striking block. Using a rawhide, resin, or metal hammer, firmly tap the wire until it is slightly flattened and even. Do not hammer where two pieces of wire overlap, this will cause breakage. Do not over hammer, this will also cause breakage.
Pulling. Pulling wire many times through a nylon jawed pliers, polishing cloth, or even just your fingers will harden it. Be careful, however, this method will heat the wire with friction! I have straightened thinner gauge (24g+) with a pliers and reused it, but like other methods, pulling will break down the pliability of the wire. If it’s straightened too many times, it will become brittle and will break. To pull wire, firmly grasp the wire at one end (I use a pliers so it doesn’t slip), and using a nylon jawed pliers or polishing cloth, pull the remainder of the wire away from the gripped end. Repeat several times until wire is springy and holds it’s shape.
Heating. Heat-hardening wire requires a kiln and should not be done without using protective measures for your silver and for yourself. Use protective eye gear and tools to remove items from the kiln.
Protect your sterling wire from oxygen exposure by covering the wire with flux, a substance which can be brushed on the wire to protect it. Any easy or medium solders in your piece will flow at the temperatures needed to harden the wire, so heating may not be the best method if you have solders in your piece.
The piece should be heated to 1292°F-1346°F (700°C-730°C) for 30-60 minutes, adjusting for solder temperatures if needed. (Adjust to 1000°F-1200°F for 30-60 minutes for soldered pieces.) Remove the piece from the heat and quench in water; reheat piece again at 572°F (300°C) and hold for 30-60 minutes.
Over time, most pieces will become work hardened simply by the virtue of “being worked.” If you find a component of your piece has become stiff and unpliable while creating, use caution so that it doesn’t break as you are finishing your work. With some pieces, you may actually want to put a hardened component aside and remake it if you need to continue to work with that piece.