ECN Forum Forums General Topics of the Trade General Discussion Area Old wire question

I'm sure the original reason for tinning the cores was to protect the copper from chemicals in rubber insulation. If I recall correctly early PVC insulated cable in UK was still plated, then it occured to someone that this was a needless cost, and bare copper in PVC started.

Exactly. The manufacturing process of rubber involves vulcanisation, which is done using sulfur. The sulfur would corrode copper, therefore any rubber isolated copper wire is tinned.

Many people mistake tinned copper for aluminium.

Even today's rubber cords have tinned copper wires (H05RR-F and H07RN-F are the European designations).

I didn't think they used real rubber for anything these days.

Well, synthetic rubber is quite similar (at least the manufacturing process), but apparently even real rubber is still used (in the European wire designations R is synthetic rubber and N is real and there are both RN and RR cords, the first letter is the conductor isolation, the second the outer sheath).

Also in the old K&T days, the EC would solder all of their splices. Then they would wrap it with rubber tape, and then friction tape over that.