The claim is discussed at The Art of Manliness, as quoted from the book Shaving Made Easy (1824):
. . . the author argues that the idea that a soft beard gives a better shave is a bunch of bunk and that hot water should be avoided:
A hair, as is well known, is a tube composed of a hard fibrous substance, growing from a bulb or root, which secretes an oily matter. This oil works its way up through the hair, and by permeating all parts, renders the hair soft and pliable. Now in this natural oily condition, it is very difficult to cut the hair with a razor, and it becomes even more difficult if the beard be made still softer by the application of hot water. Many do this, and it is no wonder they find shaving difficult. When this is done, the hairs become soft and limp, and the razor will either slip over them entirely, or else cut partly into them, bend them back and shave them lengthwise, all the while pulling and straining them at the roots, and making the process of shaving most painful.
(emphasis presumably added by artofmanliness.com)
The article itself discusses the claim, and its possible merits as well as possible shortcomings. Simply reasoning through the arguments, one can make a strong case for both cold-water shaving and hot-water shaving.
So I'm curious if there are any studies on the matter that show that a softer beard leads to a closer shave (hot water theory), or if a coarser beard leads to a closer shave (cold water theory).
I know there is a related question here, which touches on related topics, but doesn't really address the claim that a coarser beard, promoted by cold water, makes for a closer or worse shave.
For clarity, the specific claim I'm interested in is: Shaving with cold water produces a closer shave than hot water due to the softening effect of hot water which causes the razor to slide over the hair, rather than cutting it.
