The old Debate..... Copper or Aluminium
Frankly, I think there is no choice but to use copper wire when undertaking a full refinement project on an old bonsai.
There is no substitute for high quality, well softened copper wire. Many of our students have been 'converted' to the exclusive use of copper for their bonsai work.
Used correctly, well softened copper wire is easy to apply, and most importantly, smaller gauges (than aluminium) can be applied with little or no impact on the look of a bonsai.