I have been puzzling over why the sharpeners that I have used for razors have all worked well to create a shaving edge, when for others the type or grit rating of a stone seems to matter a great deal.

As an experiment, I tried different sharpening surfaces of increasingly coarser grit rating, eventually ending up with an old 1"x3" silicon carbide pocket stone of approximately 300 grit. As one might expect, the edge produced by the coarser grits were rougher, even though all of them when used with care produced arm-hair-popping edges.

However, after a moderate amount of careful and deliberate yet purposeful stropping on linen and leather the edge off even the coarsest of stones smoothed out considerably, providing a smooth and comfortable shave. It appears that just about any abrasive surface can be a good sharpener, but the strop is the thing that turns a sharp knife into a razor.