Tag: stropping

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 #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.

Post #1688: Winning the Game of Razors-and-Blades.

 

When I started this series of posts, I was bewildered by the market for wet shaving.    Four questions stood out.  Really, two pairs:  One about economics, one about performance:

  1. Why do manufacturers keep coming up with ever-more-absurd gimmicks for shaving cartridges?
  2. Why does a shaving cartridge typically cost a buck or more, but a double-edged razor blade costs ten cents?
  3. Why do some people report getting a ludicrously high number of shaves from a single blade or cartridge, while others report re-use in the low single digits, for the exact same blade or cartridge?
  4. Is any of the folklore around ways to extend the life of a razor blade true?

After doing my research, I reached a state of razor enlightenment.  It all makes perfect sense.  So let me start by ‘splaining what I think I know.  Then finish with a short discussion of stropping. Continue reading Post #1688: Winning the Game of Razors-and-Blades.

Post #1687: Razor blades, some economic footnotes

 

I set out to compare modern prices for razor blades to prices from earlier eras.  I got a lot more than I bargained for.  Turns out, there really is nothing new under the sun.  Except that razor blades have gotten a lot cheaper over time.

The basic question is, how cheap are modern razor blades?  Compared to what they would have cost historically, that is.

But the fun part is the 1918 Sears & Roebuck catalog.  This post is worth it for that alone.

 

They cost how much?

If you wanted to know about historical food prices, or typical rents, or average family income, or the cost of gasoline from bygone eras, you can find that information.  Those were all important commodities, and their prices were duly tracked and recorded.

By contrast, there’s no such luck for a cheap disposable product like a razor blade.  Nobody really much cared about them, in the sense of preserving their prices for history.  Nobody systematically recorded information about them.  And that makes it hard to find out what they used to cost, way back when.

Initially, all I could do was look for bits and pieces of advertising.

Even then, the only razor company modern historians much care about is Gillette.  And Gillette was not only a super-premium product, Gillette also played fast-and-loose with their pricing, owing to patents on some key aspects of safety razors early in that era.

In fact, there is a term-of-art in economics called “razors-and-blades“, to discuss profit-maximizing strategies for companies who sell razor handles that will only fit their razor blades.  Think inkjet cartridge pricing, and you’ll get the gist of it.  And, sure enough, once you’re locked into a handle, the manufacturer tries to extract the as much money as possible in the cartridges.

Let me start with Gillette’s list price for blades.

I am supposed to say something like “Gillette introduced the safety razor in 1904”, but that’s not even remotely true.   One can find ads for “safety razors” for many decades prior to that, all with the same basic design of a blade contained in some sort of housing, to make it hard to cut yourself.

What Gillette actually invented was the cheap, stamped-steel disposable razor blade (per Wikipedia).  And, of course, the razors that would use those blades.  Before Gillette, most safety razors had a permanent blade, designed to be re-sharpened.  Gillette got the idea to do away with a permanent, knife-like razor and substitute a disposable blade.

At that time, Gillette’s razor was marketed as a superior and more sanitary way to shave, owing to the reduced likelihood of nicks and cuts from shaving.  It commanded an appropriately premium price.

From 1904, until his patents ran out around 1924, Gillette razor blades were priced at 12 for a dollar, or 8.3 cents per blade.  That was the list price, and some sources suggest that discounting was common.

But taking that 8.3 cents at face value, I’ll translate that to current dollars using the BLS inflation calculator.  That only goes back to 1913, but it tells us that 8.3 cents, in 1913, is the equivalent of just over $2.50 in today’s (December 2022) money.  Per blade.

As noted in prior posts, current prices on double-edge razor blades range from about 5 cents each at the low end, to about 40 cents each for high-end Japanese Feather brand blades.   It’s reasonable to say you have your pick of medium-quality blades around 10 cents each.  (Those are all Amazon prices for lots of 100 blades.)

Thus a modern stainless-steel quality razor blade costs about 4 percent of what a name-brand, list-price Gillette razor blade originally cost.

But wait, there’s more.  Average (family, I think) income in that era was about 750 dollars per year.  (Based on various sources).  Median family income today is about $71,000.  So, as a fraction of a year’s income, a modern 10-cent razor blade is just 1.3 percent as costly as Gillette’s original 8.3 cent blade.

Thank goodness for Sears & Roebuck.

But wait:  Gillette was not the only blade on the market, it was just the best-advertised.  And likely the most expensive.  A comparison to the Gillette list price overstates how costly razor blades were, on average, at the dawn of the disposable razor blade.  Unfortunately, the earliest pricing I can find on other blades dates to the WWI era.

I stumbled across a University of Missouri collection of old mail-order catalogs, all scanned and available on-line.  You can get access to from this URL:  https://libraryguides.missouri.edu/pricesandwages/1910-1919.

With that in hand, it’s just a question of looking up razors in any year’s catalog and see what’s on offer in the Sears & Roebuck.  And it’s a real eye-opener.

Let me take the 1918 Sears and Roebuck catalog, despite that being in the middle of WWI.  The source for all the images below is page 1321 of the 1918 Sears and Roebuck catalog, via the University of Illinois.  Clicking this link should take you to a page that’s about 20 pages earlier in the catalog.  Just page down to get to razors.

The first surprise is that stainless steel blade are NOT a 1960s invention.  Check out this 1918 Sears & Roebuck ad, for a razor and 12 chromium steel blades.  While technically incorrect, the term “chromium steel” is often used interchangeably with “stainless steel”, for the simple reason that it behaves like common stainless.  It’s very hard, and it’s rust-proof.

Second, as is true today, you could also purchase carbon steel blades.  Oddly, you will note that the chrome steel blades are NOT a premium product.  At 12 for 38 cents, they are actually cheaper than the “crucible steel” blades at 5 for 20 cents.  (I believe that, in that era, “crucible steel” was a catch-all term for higher-quality steel carbon steel, free of inclusions or impurities.)

Third, Gillette’s stuff was, indeed, pricey.  Here you can see Gillette blades at 6 for 39 cents.  That’s about twice the price of the most expensive blade on the illustration above.  The complete shaving outfit from Gillette was four times the price of a similar outfit from the off brand.  (Also, what’s with “We do not exchange old blades.”?)

Finally, re-sharpening blades by stropping must have been common practice.  Not only do most of the razor outfits include “stropping handles”, Sears sold two different stropping devices, one to fit Gillette blades and one to fit most other blades.  This comports with the findings from my tests, where stropping definitely cleaned up and re-formed the razor edge of a used blade.

I now wonder whether stropping might have been more effective on old-style (softer) carbon-steel blades, than on chromium steel.  That’s sure the case with knife sharpening.  It’s vastly easier to sharpen a high-carbon steel blade on a whetstone than it is to sharpen a stainless blade.  Perhaps that explains the lack of premium pricing for chromium steel blades in that era?

The calculation, redone.

The cheapest blades offered above appear to be the 12-for-38-cent chromium steel ones, or about 3 cents per blade. In addition, with all that stropping going on, I bet those blades were used longer than modern blades are.  But I have no way to factor that into my calculation, absent any data on average shaves per blade in that era.

At face value, then, the best bargain on blades in the 1918 Sears & Roebuck catalog translates to about 66 cents per blade in modern money (using January 1918 as the basis for pricing, WWI saw a brief but very sharp round of inflation in the U.S.)

Or, crazily enough, just about what a low-end name-brand disposable cartridge costs today.  Still a good bit of money relative to the average family income.  But not nearly as expensive as the list price for Gillette blades would have suggested.

Really, almost the only structural difference between the 1918 market and the modern market is that disposable blades had not yet been standardized.  Gillette blades fit Gillette razors.  (Again, just like disposable cartridges today.)  Other brands seemed to have adopted a more-nearly-interchangeable standard.

If I had to point to one subtle-but-important difference, it’s in the quantities.  Recall, this is a mail-order catalog, with all the time lags that implies.  And yet, no razor blades were offered in lots larger than 12.  And everybody seemed to offer either a stropping machine or a manual strop for use on their blades.  Together, this suggests to me that you were expected to use each blade for quite a long time.

As opposed to Amazon, today, where almost any blade you’d care to buy can be had in a box of 100.  And “strops” for disposable razor blades are niche-market oddities.  Which both suggest that we probably re-use blades a lot less in the modern world than they did back in 1918.