I’m replacing some outlets in my 1950s home that were originally split (via broken tab) across two circuits, so that I can get them back on a single circuit.

When replacing the Leviton outlets with new Leviton outlets I saw that the copper wire had some significant dark gray colored coating. Picture attached: here

Didn’t come off with rubbing alcohol so I’m figuring it’s a patina and not dirt.

The new outlets have much better contact due to the U bracket that pinches the wire down, and I have a nice tight C shape going in the direction of the screw thread.

Is this sufficient for the 15A outlet replacement? Do I need to clean off the wire?

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    Do be very aware that the old cloth/rubber insulation on that wire is now brittle with age and is likely to crack as you're working on it, leaving you with a different, but still dangerous situation. Honestly, the best bet for stuff this old is to leave it alone or replace all the wire involved. You've come this far, may as well finish this job, but be conscious of this issue before embarking on any future projects.
    – FreeMan
    Jan 3, 2023 at 14:50
  • @FreeMan Yeah I had heard the same thing. I was careful to be quite gentle with it. I'd prefer to replace it as well, but these old homes have 'octopus' wiring where everything was run through the ceiling for some bizarre reason.
    – Wisteso
    Jan 5, 2023 at 2:27

1 Answer 1


It shouldn't matter unless the wire got hot enough to lose the annealing, in which case the outlet you replaced would probably have burn marks on it. I've used a bit of steel wool or fine sandpaper to clean wires before when they look funky. A nice tight screw should provide plenty of contact, though, so it's not strictly necessary.

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