As Birnando said, stropping doesn't sharpen, exactly; we are burnishing the edge. Metal is removed because as the tiny little "teeth" - more like tabs really - that are bent by the act of shaving are straightened some of them break off. It is not removed by friction as one might think intuitively.

Consider also that when a cordovan shell strop eventually begins to lose its surface finish.. we apply hard carnauba wax to restore it and polish the bejabbers out of it. It's quite a slick surface yet many feel that we get our best edges from shell strops. Truth be told, I doubt that there is any measurable difference in the edge produced by light or heavy draw strops, it's really a matter of personal preference.


rs,
Tack