Category: Analysis

Anything that I have tested empirically, or explain with detailed calculations, or just generally bother to get all the facts straight.

Post #1701: Prius Prime warranty documents. I laughed. I cried.

This post started off as a little analysis of electric vehicle battery life, but soon went off the rails.

As it stands, it’s probably useful only if you are considering buying a plug-in hybrid electric vehicle (PHEV).  Particularly a Toyota plug-in vehicle.  If you are, it may be well worth reading.

To be clear, my wife’s 2021 Prius Prime is running fine.  No problems.  Then again, it’s less than two years old.

The upshot is that I have more-or-less no warranty on the PHEV battery in my Prius Prime.  Which is not at all how it looks, if you read the description of the warranty on Toyota’s website.  Nor how it looks, if you look at Federal legal warranty requirements on EV batteries.

Ultimately, this is a story about about a loophole in a well-intentioned Federal regulation.  And what you can learn when you bite the bullet and actually read your car’s owner’s manual.  Including the footnotes.

Critically, it means you shouldn’t drive one of these cars to use the least gasoline you can, right now.  No matter how enjoyable the resulting bragging rights might be.  You should drive them to preserve the life of the battery for as long as possible.  And those are two quite different driving strategies.

Background

The Federal government requires that all electric vehicles (EVs) sold in the U.S. include at least an 8-year, 100,000-mile warranty on the EV battery.  That’s a floor, not a limit.

California require 10 years/150,000 miles.

And, of course, some manufacturers may offer more than that.  Although most offer the US mandated 8/100,000, Toyota chose to offer the California-level warranty for all cars sold in the U.S.  So, my wife’s Prius Prime battery is covered by a 10-year, 150,000 mile warranty.

I just looked that up in the warranty documents that came with the owner’s manual.

I laughed.  Lucky me.  Go Toyota!  That battery must be bulletproof.  I’m gonna drive the heck out of it, to be sure I get my money’s worth.

But this is PHEV.  How can they do that?

Then I started thinking about that, and something didn’t quite add up.

The key thing you should realize is that using a battery for PHEV just beats the crap out of it, compared to using it in an electric vehicle.  Allow me to explain.

By and large, the main determinant of lithium ion battery pack life is the amount of electricity you run through it.  The industry standard is based on the number of full charge/discharge cycles the battery pack can take before it loses 20 percent of its capacity.  (If you only do a fraction of a full charge or discharge, you count that fraction toward the total).

(Separately, there’s “calendar aging” in addition to charge/discharge cycles, but that’s for another day.)

Because a PHEV battery is small, a given amount of driving will run you through a lot more charge/discharge cycles than you would in a full EV.  For example, a 30-mile daily work commute would put about five cycles per week on the Prius Prime battery, but only half a cycle per week on one of the upper-end 300+ range Teslas.

If you were to put batteries with the same chemistry and construction in a Prime and a Tesla, and drove those cars the same way (which would never actually happen, as any Tesla driver will attest), all other things equal, the battery in the Prime will fail way, way before the battery in the Tesla.

Let me put some real-world numbers on that.  At this point, Tesla’s battery chemistry may be a bit older than the current best.  But not by much.  Those Tesla battery packs are supposed to go 1500 full charge/discharge cycles before failure.

At 1500 full cycles, then:

  • A Tesla with a 300-mile range would travel (1500 x 300 = ) 450,000 miles to battery failure.  This is why you’ll hear Tesla owners say their batteries are good for half-a-million miles.
  • A Prime, with a 30-mile range, would travel (1500 x 30 = ) 45,000 miles to battery failure.  (Assuming all travel was done on electricity.)

Even assuming something more normal — that only half the Prime miles are traveled on the battery — the Prime, with a Tesla-like battery chemistry, would still be seeing frequent battery failures around 90,000 miles.

How can Toyota warrant those batteries for 150,000 miles?

Is the Toyota battery that much better than the Tesla battery?  (After all, it was developed a lot more recently, and batteries have been improving.)  But still, even as much as I am something of a Toyota fanboy, for the longevity of their vehicles on average, something about this didn’t quite add up.

Warranty?  Not really.

Now we get to the part where I cried, from reading the owner’s manual.

To get to the punchline, the joker in all of this — the Federal regulation, and the Toyota warranty — is what you mean by “battery failure”.  Sure, the Feds require that you warranty the battery against failure for 8 years or 100,000 miles.  But the manufacturer gets to define what “battery failure” means.

You can easily find examples on-line.  Tesla adopts a 70% threshold for battery failure.  If you lose more than 30% of your range, in your first eight years of ownership, they’ll replace the battery.  Nissan uses a 75% threshold for the Leaf, but seems to measure it in a somewhat non-standard way.  VW uses a 75% threshold.

Those are all EVs.  Where the only way to make the car go is electricity.

But the Prius Prime is a PHEV.  Electricity is not the only way to make the car run.  It can run as either an EV, or as a standard gas hybrid.

For the PHEV function of the Prius, Toyota effectively adopts a threshold of 0%, for battery failure.  As long as the battery is good enough to run the car in hybrid (gas) mode, then according to Toyota, it hasn’t failed.  Which means that if my PHEV range drops to zero, well, tough.  As long as it’ll still run as a standard Prius, the fact that it has no PHEV range does not qualify the battery as having failed.

Or, as Toyota puts it, loss of range over time is normal, and is not covered by the warranty.

The upshot is that I have literally no warranty on the PHEV function of the Prius Prime.  A fact that — trust me on this — you would never figure out by looking at Toyota’s website.  Or, near as I can tell, anywhere else.

Based on the literal Toyota warranty documents, mere loss of capacity is not failure.  Up to and including all PHEV capacity.  If my electric range dropped to zero tomorrow, but there was still enough battery left to run it as a gas hybrid,  I’d have to eat the cost of a fix, to restore PHEV capacity.

Moral of the story:  Read The Fine Manual (RTFM).

A change of decoration is in order

Now that I know the full scoop — that far from offering a 150,000 mile on the PHEV function of the battery, Toyota offers zero — I need to change a few things about the way I drive that car.

Or, putting it bluntly, I’ve been pretty stupid about how I drove the Prius Prime.  I’ve been using that battery like there’s no tomorrow.  Because, hey, with a 150,000 mile guarantee, I assumed there was no tomorrow.   I assumed Toyota built that well enough that I’d see no serious degradation of PHEV range for the first 150,000 miles or so.  And I now realize that was all just my misunderstanding of the fine print of the warranty.

I’ve been living in a fool’s paradise by trying to burn as little gasoline as possible.  Look at me, see how environmentally conscious I am.  All the while, fully understanding that EVs trade off battery wear and tear for gasoline consumption.  I just stupidly believed the 150,000 mile warranty assumed me that the tradeoff in the Prime was minimal.  When the reality is that if I drive all-battery now, chances are I’m going to end up driving all-gas later.

And that changes now.  From this day forward, I drive for minimal battery wear-and-tear.  Ultimately, the longer the battery lasts, the more gasoline I will save in the long run.

First, I’m going to stop doing highway driving in EV mode.  One of the nicest surprises of the Prius Prime is that the EV side of it was more than adequate to do highway driving.  So my habit was simply to run down the battery, no matter what the trip was.  And if that meant getting on the interstate in EV mode, no problem.  But I see in forums for other PHEVs that highway driving in EV mode is discouraged, owing to high battery drain.  So from now on, if we’re on the highway, we’ll be burning gasoline.

Second, I’m going to punch the EV Auto button every time I get in the car.  Arguably the least-well explained controls on the Prius Prime are the three buttons that determine mode-of-propulsion.  (This next bit will only make sense to Prime owners).

  • The one on the left is for pedal feel.  Ignore it for this post.
  • The one in the middle lets you choose to lock the car into EV mode, or into standard Prius Hybrid mode.  (Labeled as EV/HV mode.)
  • The one on the far right lets the car choose which mode is best.  (Confusingly labeled as EV Auto mode).

Again, I should have known better.  With all things Prius the right answer is always “let the car decide what to do”.  In “EV Auto” mode, the car will kick on the gas engine under higher loads, and so forth, as it sees fit.  Avoiding high loads on the battery should be good for longevity.

For whatever reason, Toyota makes EV Mode the unchangeable default at startup.  (Plausibly, because they knew their customers were a bunch of eco-nerds like me.)  So from now on, punching the EV Auto button after hitting start is going to be SOP.

Third, I’ve bought a countdown timer to prevent the battery from charging to 100%.  The owner’s manual offers some mostly-lame advice on extending battery life.  But one useful thing it suggests is to use the charge scheduling function so that the car is fully charged just before you use it.  The inference (actually a well-known phenomenon) is that leaving a lithium-ion battery in a high state-of-charge puts wear-and-tear on it.  We have no fixed schedule, so I’m going to do the next best thing.  Based on state-of-charge when we park the car, I’m going to dial in all but the last hour of required charging.  At that point, I’ll either typically use the car starting from 80% charged, or be smart enough to plug in an hour before I intend to use it.

Conclusion, and loophole, defined.

Anyway, it all boils down to a loophole.

If you buy a hybrid, with a battery warranty, you know what that means. It’s black-and-white.  It means the battery has to be in good enough shape to run that hybrid.  On a Prius, when the hybrid battery fails, the car is un-driveable.  Hence, a 100,000 mile warranty on the hybrid battery was easily understood.

If you buy an EV, with a battery warranty, you know that that means, even it it isn’t as crystal-clear as for a hybrid.  It means that the manufacturer will replace the battery if your loss-of-range exceeds a clearly stated amount.

But if you buy a combination EV-hybrid — a PHEV — your warranty gets lost in the cracks.  You buy it for the EV, but you only get a hybrid’s worth of warranty on the battery.  If the battery fails so badly that the car won’t run as a hybrid, they’ll replace it.  Otherwise, tough luck.

And not only did I not realize that, not only was that hugely unclear from Toyota’s promotional materials, but I’ve been driving the car as if that 150,000 mile warranty meant that Toyota expected that much usable PHEV life out of the car.  When, in fact, that’s just not true.

Not that I think Toyota would have made an inferior product.  But when Toyota said that they expect the battery to last the life of the car, I mistakenly thought that meant the PHEV functionality would last the life of the car.  Which I now seriously doubt.

So I’ve gone from a false sense of certainty, as to how this car will perform in the future, to a high degree of uncertainty about it.  Doesn’t mean its going to run like a three-legged dog at 100K miles.  But it might.  Which would be very un-Toyota-like, in my experience.

I should have known better.  It was the worst sort of magical thinking.

I was living in an eco-Fool’s paradise.  And that changes today.

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 #1696: An historical note on the current Xbox kerfuffle

 

A well-known energy hog of long standing

When the recent manufactured controversy over the Microsoft Xbox hit the papers, it resonated with me.

Probably 15 years ago, we bought a gaming console for our kids.  (For the kids, of course, because we adults would never consider wasting time playing video games.)

We bought a Nintendo Wii.  Not due to the quality of the gaming, but because the Wii console used about one-fifth the energy of the Xbox and similar alternatives.  (Ask me what screen I finally got to on Wii Tanks.)  The Wii had a lot of other interesting features — not the least of which was the Mii parade above.  But the main reason I picked it was that it had a vastly lower carbon footprint than the alternatives at the time.

At the time, the characterization of Xbox energy use was that leaving an Xbox running was like leaving your fridge door wide open.  It literally used as much power as the typical American fridge.

That does not appear to have changed in the past couple of decades.  Exactly how much energy a gaming console uses depends on what you’re doing. But it’s clear that running a graphics-intensive game, on an Xbox, and using some modest-sized display, could easily consume 300 watts.  

Here’s a site with a nice table showing typical ranges of energy consumption for home gaming consoles.  In particular, they have a nice table for the PS4, showing that the difference between letting the machine run, unused, and putting it on standby, is about 85 watts.  That matches my recollection for the Xbox.

And, doing just the tiniest bit of math, if you let that game console run at idle all the time (i.e., showing the menu), that will cost you about 750 KWH per year, compared to powering it down to standby mode.  That 750 KWH is, in fact, more than the average U.S. fridge, per year.

The upshot is that, as I recalled, if you don’t enforce turning your Xbox off, but instead just leave it idling, the additional electricity cost is more than the cost of running a refrigerator.

What did Microsoft actually just do?  Sleep versus Shutdown, or about 130 KWH per year in energy savings.

As is typical with modern news-righteousness, everybody seems to start yelling before you can get a clear picture of what just happened.

If you want a clear explanation, start here.

At issue is the difference between Sleep mode (with instant-on), and Shutdown mode (where it takes about 15 seconds for the Xbox to reboot).  Just as with your laptop, one of those keeps everything in memory, keeps memory warm, and uses more power.   The other one writes things off to storage, then more-or-less turns the machine off.

Sleep consumes perhaps 15 watts, while shutdown mode consumes just 0.5 watts. Which doesn’t sound like much, but for an Xbox continuously plugged in, the 15 watt Sleep mode consumes about 130 KWH per year more than the 0.5 watt Shutdown mode.

Just FYI, that’s enough electricity to power my wife’s Prius Prime for about 750 city miles of driving.  At the prices I pay in Virginia, that’s about $15 worth of electricity per year.

In the past, Sleep was the default mode.  But starting in March 2022, Microsoft change the default to Shutdown, rather than Sleep, for newly-manufactured units.  So, to be clear, this new default has been in place for almost a year, on newly-purchased units.

The current controversy arose because Microsoft is updating the software on older Xbox units to make them match the standard that has been in place for about a year, for new units.  That is, they are going to make Shutdown the default.

Users can override that if they wish.

In my experience, you don’t scrape the bottom of the barrel until the barrel is empty.

I don’t know how the party of Teddy Roosevelt ended up being the pro-energy-consumption party.  But that seems to characterize the Republican party today.  Coal is good.  Renewables are bad.  Energy use is good.  Energy conservation is bad.

At root, this is a controversy about a manufacturer choosing to make the software on older gaming consoles match the software that it has put on consoles manufactured for the past year.  Mainly, this changed the default “off” setting from Sleep to Shutdown, which I calculate should save about 130 KWH per year per unit.

Near as I can tell, Microsoft updates the software on my computer any damn time it pleases.  And I actually depend on the computer to get along in the real world.  How on earth this update to gaming-console software became such a cause célèbre among the Right, I cannot even begin to fathom.

But, ultimately, I think it’s a good sign.  If that’s the biggest thing they have to complain about, then things must be going pretty well.

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.

Post #1692: Strop-a-Palooza, the finale. Use a knife steel to strop stainless-steel razor blades

 

Edit:  Nope. See below.  Honing a worn stainless-steel blade with a knife steel made the edges look a lot better.  But the blade still shaves badly.  And I have no idea why.

I think I’ve figured out a possibly-effective way to strop or hone a stainless steel razor blade.  Possibly.  Use a sharpening steel.  The thing pictured at the top of the post.

Don’t use an abrasive (e.g., diamond) steel.  Use a common carbon-steel knife sharpening rod.  The last post demonstrated that you can’t abrade much off the edge before the blade is ruined for shaving.

Use the “pull” technique.   Weirdly enough, half the experts on Youtube pull the blade across the steel.  Half push the blade, as if you were cutting into the steel.  That suggests to me that this works either way.  And pulling a razor blade is going to be a lot easier.  Like this technique (Youtube link).

Hold the blade at very shallow angle to the knife steel.  Start at one side of the edge, and pull it across and up the steel.  Flip and repeat as often as you want, because, based no seemingly expert authority, it’s almost impossible to over-steel a knife edge.

I’m not entirely sure this works, but it’s the best I’ve come up with, and it seems to do something.

For sure, this does nothing for any chips in the blade edge that are large enough to be visible with a microscope.  So if a blade edge is badly eroded, honing it in this fashion isn’t going to fix it.  But, that’s fair, as honing or stropping isn’t supposed to repair a damaged cutting edge.  Those really just clean up the very final finish on an otherwise sound cutting edge.

But, maybe it does something to the very edge of the blade.  After vigorous stropping in this fashion, the stropped edge of a razor blade feels sharper when run across the ball of the finger.  So much so that I can tell one edge from the other in a blind test.

Unfortunately, I have no other evidence that this is actually doing anything.  Whatever is happening at the very knife-edge of the steel is far too small for me to see with my crude microscope.  My home-made sharpness tester had too high a variance to tell me much.  And, with one blind shave test, I can’t really feel any difference in shaving.

Edit:  Finally, after 11 shaves with one Personna blade and Barbasol, I judged the shave to be inadequate.  Here’s a contrast of the worn blade and a new blade, after that 11th shave.  You can clearly see that the new edge is perfectly straight, but that the worn edge has quite a ragged appearance. 

(Parenthetically, you can see what a difference shaving cream makes relative to Dove soap.  Unlike my used blades after soap shaving, on this blade there are no huge nicks in the edge, just an uneven razor edge.)

This amount of edge wear is enough to cause me to change to a fresh blade. 

I did my best to see whether or not the blade was any narrower, per my prior experiment in sharpening a blade.  As far as I tell, it’s not. So I’m not wearing out the blade by making it too small to give a good shave. (If that were true, there would be no point in proceeding, because I can’t restore the blade to its original width.)  I’m wearing out the blade by giving it a ragged razor edge.

So, what the heck.  I carefully steeled/honed that worn blade.  Held the blade in my hand, and gave it about ten strokes across the steel, on each edge, flipping the blade with each stroke. 

Below you see two views of the same pair of blades after passing the worn blade over the knife steel.  By eye, the worn edge now appears somewhat less ragged.  Not perfect, but significantly straighter.  Which, I think, is roughly what a knife steel ought to do.  Clean up the very tip of the razor edge of the blade.

I still don’t know if this improved the blade enough that it can still used.  But I’m going to try shaving with it tomorrow.  (Honestly, it’s hard even to be sure that I’m not kidding myself about the steeled edge being straighter.)  Shaving is clearly going to be a subjective test, and if I’d thought about it, I’d have steeled just one edge, so I could do a blind shave test of one edge versus the other.  But that’s water over the dam at this point.

I’ll re-edit this one more time, after I’ve shaved with the worn-and-carefully-steeled blade.

Final edit:  Still doesn’t shave worth a damn.  I have no idea why. 

The blade remains the correct width.  I pulled out a micrometer, and the worn blade is exactly the same edge-to-edge width as a new blade (to within the 0.01 mm resolution of the tool.) 

The blade edge looks good.  Under magnification (with a cheap USB microscope), the blade edge is nice and straight.  I’m hard pressed to tell the used blade from a new blade.

The upshot is that I have no clue why the blade won’t shave.  Possibly the blade wear goes on at a scale that I just can’t see with my current level of magnification?  I hate to leave it like that, but I can’t see any reason why this blade no longer shaves well.  But it doesn’t.

That said, this brings my razor blade deep-dive to closure.  The final question was whether or not there was anything you could do to re-sharpen a stainless-steel blade.  Edit: My answer is, yeah, maybe.  Try using a knife steel.  As of this writing, my answer is no.  As with stropping on leather, I can use a knife steel to clean up the edge, but I can’t make the blade shave well again.

Finally, I am virtually certain that all the methods you may see on the internet, for stropping a razor blade, are simply folklore.  E.g., rub the blade on the inside of a glass, strop it on denim, and so on.  These probably date back to the era of carbon-steel blades.  I’m pretty sure stainless is just too hard (or wear-resistant) for those to work.

Even a proper leather strop merely shined up and cleaned up my blade edge.  It didn’t make it any sharper or better for shaving.  Experts say that you need to use abrasives, if you plan to strop stainless on leather.  My guess is that this is good advice.  But unlike a knife blade, you can’t afford to lose even a smidgen of metal off the edge of a razor blade, or it will no longer function in a safety razor.  So I don’t think abrasives are the answer here.  But I have to note that I have not actually tried loading up a leather strop with the proper stropping abrasive and having at it.

So, the only other object commonly used for cleaning up the edge of a stainless blade, without abrading it, is a knife steel.  Knife steels definitely work on stainless knives.  There’s no reason to think they won’t work on stainless razor blades.

And, near as I can tell, yes, steeling a stainless razor blade in this fashion does something.  Kinda.  I guess?

So with that, I’m calling it a day.

 

Post #1691: Strop-a-Palooza, Part 3: Fool’s errand?

 

I’m ready to call it quits on trying to strop a stainless-steel double edge razor blade.  For now, at least.

The only thing I’m fairly sure about is that effectively honing or stropping a stainless-steel blade will probably require some sort of abrasive.  But … if I abrade away enough of the razor edge, the blade will no longer function (see prior post).

So it’s possible that this has been a fool’s errand.  Or it’s possible that I don’t have a good grasp of how much damage can and cannot be repaired by honing or stropping a stainless-steel razor blade.

Here’s a sequence of photographs, starting with a beaten-up blade, and ending with a blade that was honed using Brasso, an abrasive metal cleaner.

1: Original condition, note the nicks in the leading edge of the blade

2: After honing in a large-diameter piece of borosilicate glass.  This was a PYREX measuring cup, and best guess, that’s about the diameter that antique glass hones would have matched.  I’m not really seeing a whole lot of change in the nicks.

3: Hone on medium-diameter borosilicate.  I’m certain this was smaller diameter than implied by antique glass razor blade hones.  I’m still seeing no marked improvement in the nicks.

4:  Hone on very mall diameter borosilicate.  Maybe some of the nicks look a bit less sharp.  Maybe that’s my imagination.

5:  Leather strop, dry, 20 strokes of the razor, on 6″ strop.  The surface is nicely polished, but the edge is still a mess.

6:  Extensive honing using Brasso on medium- and small-diameter borosilicate.  The abrasives in the Brasso were evident (it felt gritty to move the blade against the glass), and maybe this smoothed down the nicks in the leading edge of the blade.

Here’s my take on all of that.

Rubbing these blades across any of the tested surfaces, without abrasives, didn’t seem to do much.  Plausibly, there’s something happening to the absolute edge of the blade.  But in terms of smoothing out those (almost microscopic) nicks in the blade, it was no go.  I think that’s consistent with expert advice to use abrasives when honing a stainless straight-razor.

Honing with abrasive Brasso on curved glass maybe did something, maybe not.  Definitely maybe kinda smoothed over some edges on the nicks in the blade.

But, at the end of the day, if you compare the rough, pitted edge in the first couple of photos, to the edge in the last photo, I’m not sure I’ve done much.

Conclusion.

For now, I’m stumped.

First, it’s possible that I simply don’t understand what honing or stropping is capable of doing to the edge of the blade.   Maybe a blade like the one above is beyond help.  In which case, I’m not sure what honing or stropping is going to do for me, for a stainless blade.  Because if the blade is in much better shape than that, chances are it shaves fine.

Second, no wet-shaving experts try to hone stainless blades.  It’s obvious, from reading well-informed discussion on wet shaving forums such as Badger and Blade, that wet-shaving afficianados will, occasionally, strop old-fashioned carbon steel razor blades.  But nobody strops stainless razor blades.  To the contrary, every mention of stainless and stropping/honing boils down to “they last longer, but you can’t strop them back into shape, the way you can with a carbon-steel blade”.  So, not even die-hard wet shaving fans mention any way to strop stainless razor blades.

Third, I already noted that stropping died out when stainless steel took over the blade market.  I am certainly that traditional stropping methods should not work (or work well, or work easily) on stainless, owing at least to the greater hardness of the steel.  Even straight razors — where stainless steel razors can be stropped — require use of an abrasive.  That tells me that traditional materials used to strop carbon steel just won’t cut it.

I’m really left with just two more things I can try.

First, I can add abrasives to the leather strop.  Plausibly, the combination of abrasives and the pliable backing will carry those abrasives into the nicks in the blade and scour them out.

The drawback to that is that the only way I have to strop a blade is to run it over the leather strop while it’s in my razor.  (Even that’s not ideal — I’m pretty sure the razor blade does not sit at the correct angle when I do that.)  In any case, I don’t want to subject my razor to the abrasives in Brasso or similar.  So I need to buy or rig up something to hold the blade, if I do that.

Second, I can buy one of those mystery devices that claims to extend the life of razor blade cartridges.  (reference, reference). Those work by stropping the stainless-steel blades contained in the razor cartridges.  Some people swear they work.  Others say they don’t.  The real question is whether I want to spend $10 on something that I’m betting is a scam.

When all is said and done, if I get motivated, I’ll try one more thing.  I’ll buy or make a device to hold the razor blade at the correct angle, and try stropping with a leather strop and the proper abrasives.

At that point, if that doesn’t do it, then I’m done.  I’ll judge that stropping or honing a stainless-steel razor blade is a fool’s errand.

Post 1690: Strop-a-palooza, part II. Sharpening doesn’t work.

Bottom line:  Sure, you can sharpen a safety-razor blade.  But it’ll no longer shave.  A modern safety razor only works when the blade edge is in exactly the right place.  If you remove even a tiny amount of metal from that razor edge, the blade edge will be recessed too far into the razor.  It will no longer cut hair well, no matter how sharp it is.

Recap

I started shaving with a safety razor in October 2012.  (I just looked up the purchase date on Amazon).  At that time, I bought a couple of “blade samplers” then settled on a 100-count box of Personna blades.

A little over a decade later, and it’s getting close to the time to buy some more blades.  So I started looking into the market for razor blades, and, by reference, for ways to extend the life of razor blades and disposable razors.

I’ve learned a lot.

Surely the most important thing I learned is that using shaving cream (rather than bar soap) radically extends the life of razor blades.  I no longer question people who report being able to use a single high-end disposable cartridge for an extended period of time.  Combine a high-fat shaving cream, quality stainless steel, and multiple blades in a cartridge, and it’s entirely plausible that some individuals can routinely use a single shaving cartridge for a month or more.

Arguably the next most important thing I’ve learned is that the level of “innovation” in disposable razor cartridges is, in fact, just as absurd as it looks.  For example, Dorco recently produced a seven-blade shaving cartridge. The increasing complexity and cost of shaving cartridges isn’t driven by a need to protect your face.  It’s driven by a need to protect profits via patents.  And since patents are only good for 20 years, manufacturers must come up with something (anything) new-and-different, so that they can compete in the economic “game of razors-and-blades”.

By contrast, the market for old-school double-edged razor blades is straight-up honestly competitive.  Every blade fits every razor, so there’s no way to lock you into a specific product.  Dozens of manufacturers compete for your dollars.  And as a result, at ten cents a blade, you have your pick of good options.  As a result, razor blades are almost unbelievable cheap, compared to what they cost at the dawn of the disposable blade.

The third thing I’ve learned is that a lot of what passes for wisdom in the “wet shaving” world is folklore.  Some of it’s true, some of it’s nonsense.  Everybody repeats it.  Nobody bothers to test it.  Except me, and the occasional kindred soul.

In particular, stainless steel razor blades have been sold in the U.S. since before WWII.  (And prior to that, non-rusting chromium steel blades were sold).  These days, you are hard-pressed to buy blades that aren’t made out of stainless.  Unlike old-style carbon steel blades, stainless doesn’t rust, so there’s no need to dry them off after use.  That should have been common knowledge since 1940, when the Sears catalog just flat-out said that a benefit of stainless blades is that you don’t need to wipe them off.  I proved that drying stainless blades does nothing, via experiment, earlier in this series of posts.  And yet, more-or-less every wet shaving site or blog you visit will tell you that you must carefully dry off your blades after use, otherwise it shortens the life of the blade.  Which, to be perfectly clear, is wrong for the 99% of modern blades that are made out of stainless steel.  And almost certainly is a holdover from the pre-1960s era when carbon-steel blades were still common.

Edit:  Nope.  See Post #1699.  I continued testing, and determined that you do need to dry your stainless-steel blades.  But the issue isn’t rust/corrosion (for stainless-steel blades), it’s water spots.  It’s due to calcium carbonate deposits from hard water.  A typical “water spot” is an order-of-magnitude thicker than the edge of a razor blade, and if you let water spots form on your blade, you end up with a dull blade.  If you live in an area with hard water, you do in fact need to dry off your blade.  Even your stainless-steel blade.

So, before I actually get around to stropping some blades, I want to ask and answer a series of questions.  These may seem obvious to you, but not to me.  If you just want to get to my first attempt at literally sharpening a stainless razor blade, skip down — the title of that section is in red

Definitions:  Sharpening versus honing versus stropping.

I am not a knife fanatic, so let me offer you my amateur understanding of the distinction between sharpening, honing, and stropping.  It boils down to how much material you’re trying to remove.  Sharpening typically uses a relatively coarse abrasive and can remove considerable amounts of metal in order to form an edge.  Honing uses much finer abrasives, removes little metal, and is more of a way to polish up an already-formed sharp edge.  Stropping ideally removes no metal, and either uses no abrasives or very fine abrasives to finish the job of polishing the razor edge of the blade.

The name of the process corresponds to the edge you’re trying to achieve, and where you are in getting to that edge.  You sharpen a lawn mower blade.  If you care, you might hone an ax after you sharpen it, to get the longest life before re-sharpening is required.  If a straight razor is in sad shape, you’d sharpen, hone, and strop it to restore the razor edge.

In the past, when the only option for blade sharpening was scraping a blade across flat stones of various sorts, that could sort-of be correlated with the motions used.  You typically sharpen an edge by moving it across the stone in the direction of cutting.  You hone an edge by moving it with approximately circular strokes and very light pressure.  You strop an edge by moving it backwards — opposite the direction of cutting — over the strop.

So, can I strop a stainless-steel razor blade?

The last thing I need to do, to finish this deep dive into understanding wet shaving, is to learn how to strop a razor blade.  In particular, how to strop a stainless-steel razor blade.  Correctly.  So that it actually sharpens the blade.

Well, yes, I can, in fact, strop a stainless-steel razor blade.  I already did that, earlier in this series (Post #1673).  Put a stainless blade in your razor, run it backward (opposite the direction of shaving) over a piece of leather, a few times, keeping a fairly steady pressure on the razor.  And you’ve just stropped the blade.  Flip and repeat.

I can do it, but does it do any good?  The results of my first attempt were mediocre.  Stropping a blade that way definitely brightened the razor edge, and seemed to remove a lot of irregularities.  But it didn’t seem to sharpen that stainless blade, and it didn’t make seem to make it shave any better.

Here’s the big if:  I’m not sure it can be done effectively.  Or, at least, not by the average user.  In my review of the history of the safety-razor market, I noted that the rise of stainless steel blades coincided with the decline in re-sharpening blades via stropping.  Early on, it was assumed that the disposable-blade user would strop those blades to maintain a keen edge.  Numerous and varied devices were sold to accomplish that task.  But those were, by and large, carbon-steel blades, which aren’t as hard as stainless.  The practice of stropping razor blades peaked in the 1930s.  And as blades got cheaper, and stainless steel took over the market, the practice of routinely stropping razor blades disappeared.

Near as I can tell, nobody offers any device currently for stropping an individual razor blade.  There are a handful of devices for stropping shaving cartridges, but I would describe them as “fringe” devices.  (Here’s a couple of examples on Amazon (reference, reference)).  They say “razor blade” when they actually mean “razor cartridge”.  And among the reasons I think of them as “fringe” devices is that their description of what stropping does (cleans, removes oxidation) is a poor match for how blade experts describe the effects of stropping (straightening, re-forming, and polishing the razor edge.)

I am absolutely sure you can strop a stainless-steel straight razor.  Experts do that all the time.  So there’s nothing about the metal, per se, that prevents stropping.  (Although the expert consensus is that a plain-leather strop is inadequate and that abrasive “compound” should be used when stropping stainless).

What I’m not sure is whether I can strop (or hone) an itty-bitty flexible stainless steel razor blade.  In some fashion that’s convenient enough that I’d be willing to do it in a routine basis.  So the problem here isn’t really one of the science.  It’s really about the engineering.

 

Question 1:  Why do they say that you can’t sharpen a double-edged razor blade?

Recall the difference between sharpen, hone, and strop, as defined above.

Even though I am not a knife fanatic, I know that “you can’t sharpen a double-edged razor blade” has to be bullshit.  You can sharpen any type of hard metal.  So of course you can sharpen a razor blade.  I could, if I chose to, pull a thoroughly dull razor blade through my kitchen knife sharpener.  And I bet it would come out sharper.

And yet, you will see this repeated as an absolutely unquestionable fact.  Everybody knows you can’t sharpen a razor blade.  It took me two weeks of playing with razors and blades before it finally dawned on me what they actually mean.  Of course you can sharpen a razor blade. But in theory, sharpening a razor blade makes it useless.

Why?  Sharpening it — removing enough material to form a new edge — would make it slightly smaller.  (And, likely, non-uniform in width.)  And a slightly smaller blade won’t work, no matter how sharp it is.

This is the end of my razor, under a microscope.  It is manufactured so that the razor blade, when clamped into a curved shape, aligns perfectly with the upper and lower edges of the razor.  That’s what puts the “safety” in this type of safety razor.  (Separately, the blade also arrives at a precisely-determined angle).  I have no way to measure how far the edge of the blade sticks out, but by eye, it’s in tenth-of-a-millimeter territory.

Bottom line:  Sure I can sharpen that.  And if I manage to scrape 0.1 mm off the edge, the blade will cease to function.  Which, given how thin the metal is, and how ham-handed I am with a sharpening stone, is pretty much a given.  So, no.  In all likelihood, I can’t sharpen a razor blade and continue to use it for shaving.

As a byproduct, I now understand that there’s an ultimate, impassable limit on razor blade re-use.  You will eventually wear them down far enough that they will cease to function.  They won’t stick out of the razor far enough to cut your hair.  No matter what miracle-of-restoration you manage to use, you can’t re-use one of these forever.

Test 1:  Run a stainless-steel razor blade through a common kitchen knife sharpener.

Might as well start the practical portion of this by running a used blade through a kitchen knife sharpener.  It’s the least-effort approach.  The questions are, does that sharpen the blade, and is the blade unusable afterwards.

Now, to be clear, this is not a smart thing to do.  If nothing else, the sharpener will be set at too wide an angle, because it’s designed for the edged of knives, not the edges of razors.  But let’s proceed and see what happens.

In this case, I’m starting with the ceramic (fine) portion of this $4 knife sharpener.  (Which, I will add, works just fine for keeping my stainless-steel kitchen knives sharp.)  The ceramic is marked as “sharpening”, but there’s some chance that it merely acts as a hone.  I can’t find a definitive answer on that.

Source:  Amazon

I marked a badly chipped section of the blade edge, attached a couple of magnets to the blade to form a little handle, then ran that through the ceramic (fine) side.   Twenty-four fairly heavy-handed passes through the ceramic (fine) sharpener, and while that chip might be a little more rounded, it’s just about as deep as when I started.  That blade edge is so rough that I can actually feel the divots as I run it through the sharpener.

OK, let me try 12 heavy-handed passes through the coarse (carbide) side.  For perspective, that’s vastly more passes than I use to dress up even a dull kitchen stainless-steel knife.  Normally, I don’t even need to touch the coarse side of the sharpener.  At the extreme, I might use five passes coarse and fine to dress the edge of a knife before (say) carving meat.

That finally reduces the nick to the point where I can’t feel it when sharpening.  But note that what I’ve done is more-or-less remove the entire second facet of the blade edge.  The nick is in the same place.  The blade is now ever-so-slightly narrower.

That said, I just tried shaving with it, and I have not narrowed it so much that it doesn’t shave at all.  It will still shave, a bit.  But it does exactly what you would expect.  By moving that edge back, it now leaves stubble.  That’s rather subjective, comparing one side of my face shaved with the sharpened edge, and one side shaved with the other edge of the same blade.  It’s a very worn blade, and neither edge gives a good shave.  But if I had to call it, yep, removing that minuscule amount of steel from the edge makes the blade forever unusable for getting a close shave.

So, I can sharpen it.  I did sharpen it.  It just won’t shave worth a damn after I did that. No matter how sharp it is.  Because it’s now too narrow.

If nothing else, I’ve learned that stainless steel razor blades seem to be extremely hard.  For sure, I don’t have to worry about accidentally sharpening them to the point where they are too narrow to function.  I really had to work at it do do that.

And I think I’ve confirmed that it’s useless to try to sharpen a razor blade.  In the technical sense of removing a significant amount of material in order to produce a more uniform blade edge.  Narrowing that razor blade by an amount that is not even visible to the naked eye was enough to render it forever worthless for use in a safety razor.

Finally, I’ll note that because I’m using a kitchen knife sharpener, I’m not sharpening the entire surface of the bevel.  The bevel of a razor blade is cut to a much narrower angle than the bevel of a typical kitchen knife.  Basically, I’m just sharpening the very tip of the razor edge.  So it’s not a huge surprise that this did little more than erode the edge.  The interesting part is how little it takes to render the blade useless.

Addendum: Are all stainless razor blades sharpened the same way initially?

Oddly enough, the answer is no.  Manufactures put a variety of different edges on their stainless steel razor blades.

The blades that I’ve been putting under a microscope so far — Personnna — were clearly ground at two different angles to form the razor edge.  It’s what I’ve termed a “faceted” edge.  That seems like a lot of effort for a 10-cent disposable item.  But it is what it is.

I’m pretty sure I’m going to erase that if I strop that blade enough.  Does that matter?  I wonder whether that’s standard practice in the industry?

Below you can see that there is no one industry standard for the final sharpening of a stainless-steel razor blade.  You’ve got everything from a simple flat edge, to a faceted (two-angle) edge, to a hollow-ground edge.

I looked at the edges from a random collection of blade brands that I happened to have on hand.  Here’s what I think the edge grinding is, based on looking at them under a crude microscope.

  • Faceted (two-angle edge):  Personna, Voshkod, Shark (I think)  Note the clear, distinct line adjacent to the extreme edge of the blade.

  • Flat-ground:  Astra, Gillette, Feather.  No line.

  • Hollow-ground:  Tiger.  You can’t see this in the still photo, but by moving the light source, it was clear that the edge was hollow-ground.

The extra effort in grinding the edge seems to have nothing to do with the quality of the blade.  Of these, Feather is almost certainly recognized as the highest-end blade offered, and Feather has a simple flat-ground edge.

In any case, as I proceed, I’m not going to worry about destroying the faceted edge of the blade by stropping. Plenty of razor blades cut just fine with a flat, single-cut edge.

Conclusion

  • Stainless steel razor blades appear to be made of extremely hard metal. It took a lot more passes to make a dent in a razor blade than it does to sharpen my stainless steel kitchen knives.  (Alternatively, some say that stainless is not hard, but has extremely good wear resistance.  I don’t much care what the technically correct explanation is.  Either way, it’s a lot harder to sharpen stainless than it is to sharpen carbon steel.)
  • Removing even tiny amounts of metal from the edge ruins the blade.
  • Manufacturers grind those final edges in all sorts of ways:  straight, facet, hollow-ground.

At the end of the day, the key practical question is whether the decline in the practice of stropping razor blades was driven by economics or technology? Did people stop doing that because blades got cheap?  Or did people stop doing that because blades started to be made out of much harder material, as the market switched from carbon steel to stainless steel.

At this point, I think I’m leaning toward technology.  As of right now, given how hard those blades appear to be, and given that stropping stainless straight razors requires abrasives, it sure looks like it’s going to be difficult or impossible to strop a dull stainless razor blade back to sharpness using any sort of common materials.

Basically, the tricks that might have worked on your grandfather’s carbon-steel blades just ain’t gonna cut it for stainless.  And I’m not at all sure what will.  I’ll give it a try in my next post.

Post #1689: Strop-a-Palooza, Part 1: Historical Perspective.

 

The last thing I need to do, to finish this deep dive into understanding wet shaving, is to learn how to strop a razor blade.  In particular, how to strop a stainless-steel razor blade.  Correctly.  So that it actually sharpens the blade.

I have no practical reason to do this.  Now that I understand the importance of using shaving cream instead of soap, I find that my razor blades last a long time.  Currently, I’m on shave #8 on a single Personna stainless steel blade, shaving with Barbasol.  I’m just starting to see the first bit of blade wear

So the blades won’t last forever.  But at that rate, I probably already own a more-than-lifetime supply of razor blades.  And so, I have no practical need to try to extend the life of a blade.

Instead, this is more a question of separating fact from fiction.  As with the rest of wet-shaving lore, when I look at ways to re-sharpen a razor blade, I see a lot of stuff that just looks nuts.  And I see a lot of clever antique devices that look downright interesting.  What’s missing is anybody taking the time actually to test these methods and determine whether or not they do, in fact, work.

So that’s the purpose of this next set of exercises.  History.  Fact vs. fiction.  Historical methods.  Ending with a practical method for stropping a stainless steel razor blade.

Just to jump ahead, I think I’ve already figured out what that’s likely to be.  It’s like to be honing the blade using polishing compound on the inside surface of a Pyrex container.  But it’s going to take me a while to explain how I got to that conclusion.

A history of razor blade stropping devices

Part 1:  Sears and Roebuck Catalog.

Source and credit:  All illustrations in this section are from Sears and Roebuck or Montgomery Ward catalogs.  All early years are from an on-line collection maintained by the University of Illinois, which you can access by starting at this link:  https://libraryguides.missouri.edu/pricesandwages/1910-1919.  Catalogs from later years are via https://christmas.musetechnical.com/

The decade of the 1930s was the heyday of stropping razor blades to re-sharpen them.  Sears offered multiple models of stropping device, including electric stroppers.  The razor blade market still appeared to be dominated by cheap (and easily stropped) carbon-steel blades, and Sears flatly stated:  “Stroppers make razor blades last longer”.

But by the time you get to WWII, electric razors were the in thing, Sears was pushing stainless steel blades, and stroppers had all-but-disappeared from the catalog. One self-stropping razor set was all that was left of the notion to strop blades to extend their life.   The more conservative Montgomery Ward still offered a stropper, but it was the same model that had been invented in the 1920s.

Of particular note:  In 1940, Sears told you that you didn’t need to dry off stainless steel blades.  That’s 80 years ago.  And people will still incorrectly tell you that you need to dry off your razor blade after each use (Post #1686).  Such is the power of folklore.

Edit:  Nope, see Post #1699.  If you live in an area with hard water, you do, in fact, need to dry off your razor blades.  The issue isn’t rust/corrosion (for stainless-steel blades), it’s that water spots (mineral deposits) coat the razor edge and dull it.  See that post for details.

As of the 1955 Sears catalog, there’s zero mention of stropping, but Sears is still offering a mix of carbon-steel and stainless-steel blades.  By 1965, razors had disappeared entirely from the Sears catalog, and Sears only offered stainless steel blades, no carbon-steel blades.  By 1975, “razor” doesn’t even appear in the index, and the only shaving options shown are electric shavers.

Decade-by-decade detail follows.

Sears & Roebuck, 1918

As I found out courtesy of the 1918 Sears and Roebuck catalog, razor blade stropping was an expected part of shaving with a safety razor at that time.  Sears sold a clever device consisting of leather rollers, a blade holder, and a crank.

Sears & Roebuck, 1924

Not much had changed by the 1924 Sears catalog.  That same stropping device (now branded Kanner’s) was sold, along with an even-more-complex “Twinplex” stropper (above).  There were also several razors marked as “self-stropping”, which appears to mean that you could attach a leather cylinder to the razor itself, which would then roll across your skin and strop the back of the blade as you shaved.

Not shown, the catalog offered a broad array of shaving soaps, largely in stick form.

Sears and Roebuck, 1936

By the time you get to the 1936 Sears & Roebuck, the stropping market had expanded, and Sears boldly claimed that “Stroppers make razor blades last longer”.  If it says it in the Sears and Roebuck, it’s so.

I see two notable changes beyond the proliferation of products.  First, there’s an electric stropper on the market.  But Sears is also offering honing stones specifically designed for honing razor blades.  Note the “Duplex Home”, with a curved side made specifically for honing razor blades.  That comes up again in the next section on stropping artifacts.

Up to this point, all razor blade stroppers had been variations on a standard leather strop.  They rolled the strop up into a cylinder.  But it was still a piece of stout leather, rubbed at the correct angle against the underside of the blade.  But now we also have a curved honing stone specifically for honing razor blades.

The other notable change was the explosion in the offerings of razor blades, and the plummeting price of blades.  Note that Sears now offered blades in bulk at less than 1 cent per blade.  So this must have been the generation when safety razors really took off.  I also note the many blade manufacturers offered chromium steel blades, which, from the consumers’ point of view, would have been indistinguishable from stainless steel.

Not shown, this catalog offered many different shaving creams.  That was a change from 1924, when only shaving soaps were listed.

Sears and Roebuck, 1940.

First, not shown, electric shavers were clearly the “in” thing.  Sears devoted almost an entire page to them.

Second, Sears was offering stainless steel blades as a premium product.  Normal carbon-steel blades were still less than a penny each.  Their stainless steel blades, advertised as long-lasting, were 6 cents each.

Of special note, way back in 1940, we already knew that there was no need to dry off a stainless steel razor blade.  Sears explicitly says that with stainless steel blades, there is “No need to wipe off”.  And yet, here we are, 80 years later, and every wet shaving site you come to still tells you how important it is to dry off your blade after use.  (See edit above — you need to dry them in areas with hard water.)

At this point, Sears is no longer offering a stropper, and offers just one “self-stropping” razor set.

Montgomery Ward, 1942

Here, I found it notable that Wards also offered stainless steel blades.   No ambiguity, with a promise that they’d never rust.  The price of bargain blades had fallen to less than a penny a blade.  As with Sears, the stainless blades were a premium product, costing 5 cents each.

Wards continued to offer the “Twinplex” stropper that had first appeared in the 1920s.

Sears & Roebuck, 1955

By this time, all the emphasis is on electric shavers.  There’s one small section for safety razors.  No mention of any type of stropping device anywhere.  Sears continues to offer both cheap carbon-steel blades and stainless steel blades.

Sears, 1965.

By the time you get to 1965, the only shavers offered by Sears are electric.  This year they featured many models of cordless electric shavers.  The offered no razors.  Certainly no strops.  And all the razor blades on offer were stainless steel.  Carbon steel blades had disappeared from the Sears catalog.

Sears, 1975

At this point, the word “razor” no longer appears in the index of the catalog.  You have to look for “shavers”.  And, sure enough, all they sell now is electric shavers.  The only vestigial nod to wet shaving is the hot shaving cream gizmo pictured above.

Part II:  I bought it on Ebay.  Other vintage razor-blade stropping devices.

Source and credit:  All illustrations in this section are from Ebay.  I will try to be sure to give a link to each individual listing that I use.

If you look on Ebay you can find examples of most of the stropping machines and self-stropping razors show in the Sears catalogs.  These are incredibly helpful for figuring out how those devices work, because the Ebay listings typically show multiple photographs from different angles.

By and large, the stropping devices shown in the Sears & Roebuck were leather cylinders, turned in some fashion, with some way to hold the blade in the proper position against the leather.  Fundamentally, they were no different from a traditional leather strop used with straight razors.  Merely made smaller and adapted to the form of the safety razor blade.

Instead, in this section I’m going to concentrate on razor-blade stropping devices other than the box-with-leather-roller types shown in the Sears and Wards catalogs.

Finally, let me be clear that I’m only interested in tools that could be used to hone or strop safety razor blades.  In particular, I need to avoid tools and devices designed for straight razors.

At the end of the day, a curved sharpening stone or even just a curved piece of hard glass appears to be the most common non-leather tool used to re-sharpen razor blades.  For those where instructions were evident, all of them said to use a light touch.  I have to assume that the curve of the stone or glass then aligns with the angle of the razor edge, and that the stone or glass itself is hard enough to strop or polish the razor edge.

Criss-Cross leather disk strop.  Click here for Ebay listing.

This is a leather disk, turned by a crank, with a blade holder sitting above the disk (in the upper right).  Put the blade in the holder, let it down onto the leather disk, and crank to strop the back of the blade.  Basically, this is just another variation on a traditional leather strop, fit to the form factor of a safety razor blade.

Curved sharpening stones

These are all sharpening stones with a curve cut into them.  You lay the blade in the curve, so that both edges touch the stone, and lightly rub it in a circular fashion.

Safety razor hone.  Click here for Ebay listing.

Safety razor hone 2.   Click for Ebay listing

Safety Razor hone 3.  Click here for Ebay listing

Curved glass strops/hones

I had never heard of using glass as a strop or hone, but there are several variations of that represented on Ebay and elsewhere.  Based on one set of instructions, I think these work just like the curved stones.  You lay your blade in the curve, edges touching the glass, press down, and just kind of move it around in a circles over the glass.

Curved glass razor hone 1.  Click here for Ebay listing.

Glass razor hone 2.  Click here for Ebay listing

Glass razor hone 3.  Click for ebay listing.

Velvet glass sharpener. Click here for Ebay listing.

Pretty sure this one works the same way as the others, you just use the inside of the glass as the curved edge of the glass.

Other/weirder stuff

Magnetic razor-blade sharpener.  Click for Ebay listing.

Well, that’s just hilarious.  I came across a modern version of this the other day.  The claim here is that by something-something-something magnetic fields something-something-something, and presto, the blade is resharpened.  It’s Science!  I assumed the modern one was a scam, and I’d bet that this is merely a 60-year-old scam.

Bakelite razor sharpener.   Click here for Ebay listing.

 

 

 

 

 

I’ve seen several models like this, mostly from Eastern Europe or the Soviet Union.  All of them have this clamshell design, with what I assume is some type of sharpening media, but I have no clue how this works.

Summary:  Some clear direction for stropping stainless steel blades.

I’m pretty sure that most common glass is not quite hard enough to be used to sharpen stainless.  Glass comes in around 5 to 6 on the Mohs scale.  Stainless, if you can put it on that scale, varies, but goes up to at least 7, depending on who;s counting.

That said, nothing would stop me from putting a little polishing or fine grinding compound on a piece of curved glass, and having at it with a stainless steel blade.

Finally, borosilicate glass (Pyrex) comes in around a 7.5 on Mohs.  So, arguably, the 21st century analog of resharpening carbon-steel blades using soda lime glass would be to resharpen stainless-steel blades using borosilicate glass.

So I think that’s the direction I’m going to take.