Re: Dull Razors

[Joseph Bellina <jbellina@SAINTMARYS.EDU>]

One of the main reasons older razor blades lasted such a short time and
newer SS blades last longer is the reduced corrosion rate of SS blades.
As a result of the corrosion, the blade edge becomes embrittled and
pieces break off for there reasons mentioned.  The hairs are thicker and
tougher than the blade edge, and it is the embrittled edge which
degrades.  Stropping can remove some of the corroded material, thus
revealing a sharpened edge.  While I hadn't thought of it before, I
suspect that shaving creams with lubricating oils tend to coat the blade
edge limiting the corrosive embrittlement.
It is also the case that SS being somewhat more ductile than hardened
steel with bend at the edge as well.  Such bending can lead to
microcrack formation which further enhances corrosion.

cheers

On Fri, 24 Sep 1999,
L. R. Cartwright (Larry) wrote:

> On Fri, 24 Sep 1999, Jim Green wrote:
> > Why do shaving razors get dull?
>
> On my way out of school this afternoon, I grabbed a microscope and brought
> it home to do a quicky examination of a couple razor blades.  As I am
> often reminded by you PHYS-L guys, physics is experimental science and I
> try to remain true to that.
>
> As I suspected, the "sharpness" of a brand new stainless steel blade at
> the microscopic level was not as slick and smooth as one might expect, but
> the edge of a used blade was absolutely devastated:  relatively "huge"
> chunks of metal torn away or bent aside, reminiscent of a lawnmower blade
> that has hit many rocks and sticks.  It would seem that hair and epidermal
> debris must be a pretty rugged landscape for the microscopically thin
> blade-edge to be repeatedly dragged through; and that hair and skin tissue
> must present quite a degree of "hardness" at that scale.
>
> As Bill suggested earlier, there may be different answers for different
> types of blades; I only looked at my Gillette Sensor stainless.
>
> Best wishes,
>
> Larry
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Larry Cartwright, Physics and Physical Science Teacher
> Charlotte High School, 378 State Street, Charlotte MI 48813
> <physics@scnc.cps.k12.mi.us> or <science@scnc.cps.k12.mi.us>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~