Copper - is there such a thing as "airhardening"?

[Renate]

I've been rummaging boxes with older wire snippets, never finished small projects, test pieces etc., and I have observed, not for the first time, that the copper not only oxydizes slightly, but also seems to have hardened a bit. I don't have a tumbler, so none of my wire has ever been hardened that way.

Am I hallucinating, or has anyone else observed this?

[laura]

yep, I think it's called natural age hardening.

[Tela]

Ditto- I read about it somewhere very recently. It DOES harden over time when exposed to air.

[kay]

Hmmm, very interesting. I was all set to strip a bunch of copper electrical wire from it's sheathing. Perhaps I will leave it be until I know what I am going to do with it.

[Tela]

Kay, when I moved into my place, there was some extra 14g sheathed copper house wire in the shed. I know it is old, at least 20 years. I strip it and use it all the time. The key is, it has been covered in a sheath, so it's fine. Even though it's 14g it is easy to work- as easy as 14g can be, anyway.

[Renate]

Oh good. I'm not hallucinating. ;D

So it must be the natural oxydizing / contact with air or whatever that causes the hardening. And I think the process can be reversed by heat (=annealing?), right?

[Tela]

Annealing should help.

I used the flame on my gas stove to burn off a patina on a tiny wireguard and it got so soft I had to trashed it. It was tiny, though.

I've never had a need to anneal metal for wirework, yet.

[shiny]

So, does this mean my copper work will get brittle over the years?
And I tumble everything, often overnight, but copper never gets really hard.

[Tela]

I'm not real sure about that answer. BUT consider this: House wiring is copper. Think of all the ends of wiring in your house exposed to the air. They can't be getting but so brittle or eveyone's house would burn down in a short number of years. I doubt it gets very hard, very fast. I have some copper jewelry test pieces that are well over 10 years old and they are only a little harder. They weren't bagged, either.

[Renate]

Shiny, I think (hope!) the becoming brittle is of relevance only with higher gauges and in particular when the wire has some movement. After all, the oxydation only takes place on the surface. Now I wonder if an anti-tarnish polish or coating would slow down or even prevent the becoming brittle?

[Renate]

Me again, with an example.
One of my early wire wrapped projects was a memory wire bracelet which I had wrapped with seed beads on approx. 28 or 30 gauge wire. After a year or two of occasional wearing, the thin wire broke at one point and the bead came off. With this kind of construction all beads have a tiny bit of movement, and maybe into the bargain I had some beginner's kinks in the wire. .
Lesson learned: thin wire + movement + time = too much. I'll try to improve that construction, that's an interesting project.

This is the bracelet, and the wire broke in the lower left pink-blue area.


(picture size edited)

[Tela]

Wow! Renate! I LOVE that bracelet! I think I've seen it before, but I still love it- all those yummy colors and things going one.

I think in your case, it was probably a matter of the wire moving too much that made it snap.

I'm not too worried about the copper getting old and brittle. Like you said, there is the patina, the anti tarnish types and even the polishing to help cut down on problems. And, anyone interested in wearing copper jewelry, like me, would store it in zip locks.

[shiny]

Good. As long as my jewelry will last for another fifty years ... I can live with that.
Thanks for the response. You're all terrific.