Lessons Learnt Today

Published at 21:00 on 12 January 2014

Braiding 10 gauge copper wire is something that sounds simple but is in practice very difficult. It’s not possible to easily get a nice, tight braid, because by the time you’ve bent it enough to braid it loosely, it’s become work hardened to the point where it needs to be annealed yet again if you want to bend it tighter. While possible, doing dozens to hundreds of mini-annealings as one braids would be such a pain that one is best off forgetting about using the braiding technique (at least if one is focused on tight braids).

It may not be classic fire scale, but heating copper to the point of annealing it makes it significantly more reactive than it is at room temperature. Reactive enough, in fact, that it instantly forms a lovely black layer of oxides. The classic boric-acid-in-denatured-alcohol barrier flux that silversmiths use does an excellent job of preventing most of that oxidation. And it’s not necessary to purchase insane quantities* of boric acid from a jewelry supply house; any drug store should have it in their first-aid section.

The barrier flux won’t prevent all oxidation. What it doesn’t prevent can be removed using what’s called a “pickle”. You don’t have to buy special “pickle compound” from a jewelry supply house; just dissolve 2 tablespoons of salt in 1 cup of vinegar. Keep it on the warm side (at least 100 °F) for best results. Since it’s winter, I just kept the jar on top of a baseboard heater today. Salt-and-vinegar was apparently the standard pickle compound before jewelery supply houses started convincing people to buy sodium bisulphate from them.† (Hence the name “pickle”, because it’s essentially a stonger, saltier version of what’s used for the food-preserving technique that goes by the same name.)

Do not under any circumstances pickle anything with dissimilar metals, unless you want to see the more reactive of the metals become electroplated with the less reactive metal. It was something of a surprise to see the brass design highlights on a bracelet turned to the same copper as the rest of the piece. Thankfully, it was a very thin layer of copper which was easily removed with some aggressive polishing.

* For some reason, they are fond of selling the stuff in minimum 5 pound lots, which would be enough to last me several lifetimes, most likely.

† In defense of the bisulphate, it does apparently last longer than the salt/vinegar mixture. For me, that’s no big problem, as I’m occasionally making jewelry as a hobby. Another plus of the salt/vinegar pickle is that commercial pickle is yet another thing that jewelry supply houses insist on selling in insanely-large (for a mere hobbyist) lots.

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