A good source of auto-grade wires is junk cars. I strip harnesses at no cost to the owner (
) and then have a good variety of colors, hashes, and gauges for almost any task.
I prefer to use marine grade when I can afford it. The local marine supply has primary wire (solid color) in most common sizes. It's a multi-stranded, double-insulated wire with each individual strand tinned.
When I think about it, all of my diy projects trend toward marine grade connectors, shrink, wire, switches. etc. Unlike automotive and m/c, marine stuff assumes it's gonna get wet with all sorts of liquids for all kinds of time.
. . .and sorry for the misinformation re: electrons and the surface of a conductor. I had been taught that in what amounted to a HF instrument class and assumed it was a universal truth.
