Power Cable Break In - Such a Change!

     When I bought my turn-of-the-century built home: much of the remaining wiring was still varnished cotton insulated.

     As cotton was recognized to be a not-so-great insulator, that kind of wiring was threaded throughout the house, captive in ceramic spools (knob and tube wiring), like this:

https://www.canadianhomeinspection.com/home-reference-library/electrical/knob-tube-wiring/

     Of course: that was before we figured out how to synthesize the plastics and rubber substitutes, that are better insulators.

     Cotton has an excellent, very low, Dielectric Constant, but: mixing it with another material will add that material's Constant to the cotton's.    

    That includes: laying the cables on the floor/carpeting.     A concept many don't understand, but: why some will hear differences, in their homes/systems, when using cable lifters.

    Here's a PDF chart to save, that may be of use far as choosing materials, for the DIY cable guys:

                               https://www.kabusa.com/Dilectric-Constants.pdf

Thanks, rodman99999 for that link, I will save it for future needs.

piaudiol,

Explain how cotton can be used in a "dielectric hybrid manner" in a power cable?

ozzy

Why does Duelund and others oil their cotton?  What's the advantage?

@twoleftears -

     This is just a guess and I suppose there may be other reasons, but, perhaps:

"Biggest issue is that it does not inhibit oxidation of the conductors. That has to be taken care through other means."