Composition of old cloth covered wire

Nov 13, 2012 4 Replies

What was the composition of that old cloth covered electrical wire? Obviously some sort of cloth. What kind? Then what was added to it to make it firm? From what I've seen it appears that some contained tar or some sort of wax. But the white and red wires were painted, and I dont think paint would adhere to wax. I'll take a wild guess and say that the earlier stuff was not the same as the later. For example the early knob and tube wire was thicker and seemed more tar-like, whereas the later stuff found in BX was of a different consistency, with less thickness.


Here's the Standard Handbook for Electrical Engineers - 1918 edition.

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Petroleum tar would quickly become brittle and break up into tiny particles. Coal tar will stay flexible for ever.

Paul

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