Please see this:
http://web.hep.uiuc.edu/home/serrede/P436/Lecture_Notes/American_Wire_Gauge.pdf
The material is really quite irrelevant. 12 AWG is 12 AWG. So a solid 12 AWG wire is what that chart in the link I provided says it is…
Human hair is about 100 microns thick. That’s about .004". So no, we are stacking about 4 hairs on top of each other…