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I have a very large antique mirror with some dense heavy wood framing it. I've stripped out some home electrical wire to use the copper ground wire as the cable that ties to the back of the mirror frame and holds it up on the wall. My question is how can I tell if the copper wire is strong enough to rely on and is it possible it will snap given time?

If I search the internet for load bearing on copper wire it refers to the wrong kind of load i.e. electrical which is not what I want to know.

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    $\begingroup$ Why not just use steel wire? It's not like the stuff is hard to find or all that expensive. $\endgroup$ May 27 '16 at 20:16
  • $\begingroup$ It was what I found available at the time. $\endgroup$
    – 6ft Dan
    May 27 '16 at 21:50
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Copper wire is not ideal as it is soft, has low tensile strength and can creep under load over time and if you are reusing old electrical wire there is no way to know whether it has small cracks in it which could exacerbate this.

The best option is to get some picture hanging wire which is designed for the purpose and is cheaply and easily available from any hardware supplier.

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  • $\begingroup$ Also, the tension in copper wire will cause "work hardening" which produces a large change in its material properties. Copper is not a good material to carry "structural" loads, period. If you don't want to use steel wire for some reason (e.g. the possibility of rust forming), brass would be a much better choice than copper. $\endgroup$
    – alephzero
    May 28 '16 at 0:40
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    $\begingroup$ To expand on the notion of 'soft' - copper wire for the overwhelming majority of electrical applications is fully annealed - the one exception is wire for use in overhead lines where it is required to support its own weight under some mechanical tension. In this case it is hard drawn. $\endgroup$ Jun 4 '16 at 12:16
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You can find a table of mechanical properties of various gages of copper and aluminum wiring here:

Wire Mechanical Properties

You just have to Google the right terms.

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