[geowak]

Does anyone know why old speaker cable 's strands of copper turn black? I have some old Monster cable and Pro audio cable, where in some places the copper wire has turned black (like it burned?) and in another cable it's just corroded, turned green. Is the cable still good enough to use?

[Captainhemo]

Oxidation will turn copper green , usually only on the outer layer.    Maybe the  ones that turned black  aren't of the   best quaility copper.... ?

-jay

[Elizabeth]

I believe the black is caused by sulphur corrosion.
Monster had a lot of funky cables corroding back in the day.
The black and the green are both bad for copper. The corrosion causes resistance. a lot of it... and the cables are scrap.

[Folsom]

Arcing will cause carbon build up. That shouldn't be happening though.

[bladesmith]

Copper oxide.

[*Scotty*]

I had some of the infamous Monster Cable back in 1987 that turned green in less than a year. There was allegedly something wrong with the vinyl formulation used in the insulation and it caused the corrosion.
Elizabeth is right the cable is scrap.
Scotty

[bladesmith]

Cut back an inch or two, and get back to some cleaner copper. Then reattach.

If it is just the exposed ends, that are turning black.

Just a thought.

[Ericus Rex]

Cut back an inch or two, and get back to some cleaner copper. Then reattach.

If it is just the exposed ends, that are turning black.

Just a thought.

This is what I'd do.  No need to scrap the cable.  Just know that the new exposed end will oxidize/corrode and you'll have to cut some fresh surface again in a year or so.  Now, if you cut away some insulation and the fresh surface is also black then scrap the cable.

[geowak]

Thanks to all for the info. Never thought about using just the remaining good copper and cutting out the bad stuff. I kinda knew that copper can have oxidation, but did not know about the bad patch of insulation Monster produced. I guess I will be able to use some of the cable, and discard the rest.
Then again I am might worry about further oxidation or corrosion, so I might just scrap it. If I can remove the insulation I might get some cash from the copper, but we are only talking about 25 to 35ft.

[Don_S]

geowak,

If you have not trashed the cable or recycled it yet.  Consider recycling at an e-waste collection site or event.  In CA Goodwill is licensed to recycle e-waste. Maybe other states have similar arrangements.  Better than the trash bin. You may even have other equipment to recycle.

[Early B.]

I have the crappy Monster cable on my HT rear speakers that was installed about 10 years ago and has turned green. It's about 70 feet of cable that's buried underneath the carpet. It's not worth the time and cost to replace it (approx. $4/foot for decent cable), so I live with it.