Annealing Copper Wire (cont.)
Increase In Work Hardening Strength
Fully annealed copper wire will increase in strength as it work-hardens by a factor of about two . In addition, it takes relatively little deformation to bring about a fair bit of this strengthening.
I estimate that the act of wiring a branch and then bending it once into some reasonable shape will increase the strength of the wire by about 50%. I don't have any strength data for copper versus aluminum with me, but, if memory serves me right, the strength of fully annealed copper is 50 to 100% higher than fully annealed aluminum. Given that aluminum does not work-harden as much as copper, this means that, once wrapped around the branch and bent a given diameter, copper will have about two to three times the strength, and thus holding power, of aluminum wire.
Large Gauge Wire
A further comment is that copper work-hardens enough that merely taking a large diameter wire off a coil will increase its strength appreciably. This can be good in the hands of one who really knows what they are doing since the stronger wire will then hold more. But, if the wiring skills are not as advanced, the wiring will be that much more difficult since they are starting with a really stiff chunk of wire (almost a rod). It is, therefore, probably a good idea to anneal really large diameter copper wire in a straight piece rather than on a coil. Of course, the other alternative is to use two or more pieces of smaller diameter wire.