Tag: razor blade life

Post #1698: Razor-blade longevity test, the redo

 

This post replaces all my prior posts on extending the life of a razor blade.  Because, I think I goofed.

Based on my most recent analysis:

Whatever it is that dulls a razor blade, short of abuse that puts big nicks in the blade, you can’t see it under a low-magnification microscope.  Blades that appear perfectly sharp, and (by measurement) retain their full width, can, nevertheless, be too dull to remove your beard.  I have no idea why.

The ONLY test for whether a razor blade remains sharp and usable is to shave with it.  Neither examining it with a low-power (USB) microscope, nor testing it with a home-made sharpness tester, provided useful information on how well a blade would shave.

Of the three things commonly cited on the internet, for extending the life of a razor blade, I now believe that:

  1. Softening your beard prior to shaving is critical for razor blade life.
  2. Drying off your razor blade — even a stainless steel blade — is necessary to keep it from dulling prematurely.
  3. Once it goes dull, there’s nothing you can do.  Stropping a dull stainless steel blade does not return it to a usable state.

Number 2 is a change from my prior posts, and that’s really the key point of this post.

Edit:  And I now know why:  Water spots.  A calcium carbonate deposit (a.k.a., water spot) is much thicker than the edge of a razor.  Tested and confirmed by comparing distilled water to tap water, Post #1699.

The upshot is, if you use shaving cream or (arguably) a high-end shaving soap, and dry your blade after each use, you’ve done your due diligence to get the most out of your razor blade or disposable shaver.  Whether more extreme measures add to that — keeping the blade stored in oil, freezing it, or whatnot — would require more analysis.

A recap and a bit of detail follows.

Recap

I’m trying to determine whether any of the suggestions for extending blade life, commonly found on the internet, actually work.

I boiled this down to:

  • Dry your blade
  • Strop your blade
  • Soften your beard.

I wanted to be as objective as possible, so I tried to avoid rating blades based on how the shave felt, figuring, there’s a lot of subjective leeway in that.  Instead, I was going to rely on how the looked, and how sharp they appeared to be, based on a home-made sharpness tester.

In hindsight, that was a mistake.  Appearance was an adequate way to judge blades if they were thoroughly abused.  But for blades that have not been abused — without visible nicks or erosion in the edge — it turns out that a sharp, usable blade looks just like a dull, unusable one.

Results.

Soften your beard/lubricate your face:  CONFIRMED

If nothing else, this razor blade test has broken me of a life-long bad shaving habit.  I shave(d) with soap.  Most recently I’ve been using Dove, because that’s supposed to have more emollients in it and be generally nicer to your skin.

And, not unrelated, I’d typically get three shaves out of a blade before I got the urge to replace it.  Maybe five, at the outside.  But by the time I got through that fifth shave, it required multiple passes of the blade and, basically, it hurt.

For this final test, I decided to shave half my face using Dove soap, and half with Barbasol.  The main active ingredient in Barbasol is stearic acid.  That’s the same as the main fat in coconut oil, and it is frequently recommended as a beard softening agent.

From the first shave, it was absolutely clear that shaving with Barbasol was a lot better than shaving with soap.  In the end, I got ten decent shaves with Barbasol, versus a typical 3 to 5 shaves with soap. 

That one is case closed, as far as I’m concerned.  I’d conservatively say that using Barbasol easily doubles blade life, relative to shaving with Dove soap.

If you want a more in-depth dive into the ingredients of shaving cream and shaving soap, see Post #1668.

Strop your stainless steel blade:  Busted

Stropping means running the blade “backward” — opposite the direction of cutting — over some suitable material.  The idea is to polish and hone the very final edge of the razor’s edge.

The practice of stropping razor blades to re-sharpen them disappeared just about the same time that stainless steel blades (above) took over the market.  I strongly suspect that this was cause-and-effect.  Stainless razor blades are just too hard (or wear resistant, take your pick) for stropping to have much effect.  I went through this in the historical perspective on stropping, Post #1689.

I have now tried all of the following, and none of it resulted in restoring a dull blade to usable status.  I.e., from the standpoint of shaving, none of this sharpened a stainless steel blade:

  • Stropping on a leather strop, blade held in razor.
  • Stropping by rubbing on the inside of a plain water glass.
  • Stropping by rubbing on the inside of a curved borosilicate glass.
    • Low curvature (measuring cup)
    • Higher curvature (oil lamp chimney base)
    • High curvature (oil lamp chimney top)
  • Stropping on borosilicate glass, with abrasive metal cleaner
  • Stropping using a standard carbon-steel knife steel.
  • Stropping using a commercial leather strop plus green “compound”.

None of that seemed to make the least bit of difference in how well the blade shaved.  In particular, using an actual commercial leather strop and compound, 30 strops, did nothing to restore a blade to usability.

Finally, literally sharpening a blade — removing significant amounts of material from the blade edge — destroys its usability.  It makes it too narrow for the safety razor, and it then leaves stubble instead of cutting cleanly.

Stropping, steeling, sharpening, and so on.  Total bust.

Dry your razor after use.  I’ll be damned.

 

For this one, I cooked up a fairly elaborate experiment to show that nothing happened to stainless steel blades if you leave them wet.  I took six blades (three new, three used), kept one edge wet for a week (either continuously, or dunked in water once a day), and kept the other edge dry.

And, by eye, there was absolutely no difference, under a low-powered microscope, between the wet and dry edges.  There was no difference in sharpness, based on my crude sharpness tester.  So I originally concluded that drying a stainless blade after every use is unnecessary.

Then the stropping experiment finally ended, I put a different razor blade in my razor.  This was one of my test blades above, and I expected it to shave like a new blade.

Well, I was half right.  One side shave just like a new blade.  The other side was so dull as to be unusable.

When I pulled it out of the razor, the unusable side was the one that had been dipped in water a few times a day, for a week, and left to dry at room temperature.

So, I’ll be damned.  I can think of no other explanation for this, other than, failing to dry off that blade, for what amounts to a couple of week’s worth of dunking, left it dull.

I may look a little more carefully at this.  I want to repeat that.  And some people say that extreme measures can preserve blade life even further.  Others claim that the dulling is due to build-up of minerals on the blade, from hard water.  So I may want to look at all of that.

But as of right now, for reasons that I absolutely cannot fathom, it appears that you do, in fact, need to dry off a stainless blade to keep a sharp edge on it.  Or, at least, failing to do that will dull the edge.

I have no clue why that is.  I’m only attesting that, based on a sample of one blind shave with one carefully-treated blade, that appears to be true.

Anyway, dry off your stainless steel blade.  Apparently confirmed.

Edit: See next post for the explanation.  It has nothing to do with rust or oxidation of a stainless-steel blade.   Post #1699.

Post #1693: Razor blade wear and tear, the final piece of the puzzle.

 

OK, I lied.  My last post was not my final post on shaving.

To complete the analysis of factors affecting razor blades, I need to document normal variation in beards.  In short:  It’s huge.  All other things equal, that almost certainly leads to huge variation in razor blade life.

This scholarly article will probably tell you more than you ever wanted to know about beard hair.   A key sentence is:

The density of beard hair follicles varies with facial area and ethnicity. Values range between 20 and 80 follicles/cm2

I interpret that to mean that, within normal variation, some guys have four times as many beard hairs (per skin area) as others.  All other things equal, that’s going to generate four-fold variation in razor blade longevity.

There is further variation in hair thickness, stiffness, shape, and so on.

With that much background variation, there really is no such thing as normal razor blade life.   There’s only what’s normal for you, and what you can plausibly do to extend it.

The only shaving technique studied in that article is wetting (hydrating) your beard.  Which I think anybody who shaves with a blade understands to some degree.

The force needed to cut a beard hair is reduced by about 20% within the first minute of water contact. After four minutes, the cutting force is reduced by 40% and does not significantly decrease further with longer hydration

This correlates well with the standard advice you’ll hear from shaving experts, which is to let your shaving soap or cream sit on your face for a minute or two before you shave.  (Both shave cream and soap lather contain water.)

Interestingly, I can find zero scholarly evidence that the fat (e.g., stearic acid) in shaving cream does anything to soften hair.  And yet, I have found that shaving cream extends blade life, compared to shaving with soap, even though both methods result in hydrating the beard prior to shaving.  Moreover, so far (shave #10 on the same blade, today) it extends blade life far beyond what you might expect from the 40% reduction in cutting force cited above.  And, all major brands of shaving cream or gel contain one of two fatty acids as their main component.

Maybe that’s strictly a skin softener?  Maybe a lot of the wear-and-tear of shaving comes from the skin, and not the hair?

Beats me.  Whatever the underlying mechanism is, it seems to work.  And every manufacturer of shaving cream seems to include it as the main ingredient after water.

I guess, now, I really will call it a day on posts about shaving.

That’s not to say that I’ve exhausted the topic.

It’s more than I’ve exhausted my willingness to track down all the nutty claims that are made about shaving and razor blades.  Every time I look, I find another one.  Today, it’s a patent claiming that dipping razor blades in 12% to 20% citric acid will extend their life at least five-fold, by preventing the formation of “mineral crystal buildup”.

Edit:  Well, as it turns out, upon further research, that’s not so nutty after all.  See Post #1699 on how water spots (calcium carbonate deposits, or “mineral crystal buildup”) can coat the razor edge and so dull the blade.

Let us never forget that you can keep your blades sharp forever by keeping them in a pyramid-shaped object.  But only if you orient it exactly with the earth’s magnetic field.  And yeah, there’s a patent for that one, too.