Agent 86 wrote:

some 14 AWG zip cord (or speaker cable). If you look close, you'll notice
that it's made up of lots (and lots) of teeney-tiny strands of wire that
fit really close together so there's not much air space between them. The
air's not particularly important, but the implication is that if you use
enough strands so they fit together tightly, you have *almost* as much
metal in a stranded wire as in a solid wire of the same gauge.

This must be one of those schoolboy mathematics exercises:
Calculate the percentage of copper in a cable of n strands.

I make it 100% for 1 strand, 88% for 2 strands, 87% for 3 strands,
83% for 4 strands and 91% for many strands.
Of course my geometry isn't what it was forty years ago.

If you want 100% copper in your multi-strand wire you must fill the gaps
with even smaller strands and sell it for $thousands per metre.

--
Eiron.