This is part of an ongoing series to test various internet-based suggestions for extending the life of a razor blade. You can see the background for this in the just-prior post.
The first thing I want to test is whether stropping a used razor blade allows it to be re-used comfortably. (Stropping means running the blade backwards — opposite to the direction of shaving — over some suitable material such as leather or denim, to polish the razor edge of the blade.)
Based on a sample of one blade, it appears to me that:
- Stropping “cleaned up” much of the raggedness of the edge of a used razor blade. This is visible in pictures below.
- Stropping did not sharpen the used blade. The stropped edge was slightly less sharp than the un-stropped edge. This is based on my home-made sharpness tester, described below.
- In a blind shaving test, I could not tell which edge of the used blade had been stropped and which had not.
There are obviously a lot of caveats here, starting with, this is a sample of one. I used one brand of stainless-steel blades (Persona), I used a leather strop, and, plausibly, my used 10-cent blade may not have been terribly worn out before I decided to replace it.
Perhaps if the blade had been made of a different material, or I’d used something other than leather for the strop, or I’d started with a really badly worn blade, things might have turned out differently.
All I can say is that for the blades I use, for the condition that I typically throw them away in, stropping made the blade edge look nicer, on a microscopic basis. But it didn’t seem to change the functionality of the blade at all. I literally could not tell the difference between the stropped and unstropped sides of the used blade when I shaved with it.
YMMV.
Details follow. I’ll likely redo this test at a later date with a thoroughly worn-out blade, to see if results change.
Background: There is no substitute for testing.
In the four+ years I’ve been writing this blog, I’ve found that much of the practical advice that is passed around the internet never gets questioned. Or tested with any sort of rigor.
Instead, your typical blogger reads up on a topic, repeats what others have said, and that’s that. Nobody bothers with even the most cursory checks to see if what they are saying is true, or even plausible. As a result, much of the practical advice you read is electronic folklore. Not that I am dissing folklore. It’s just that some folklore is true. And a lot of it is not.
Probably my favorite example of ridiculous-but-universal advice is this rule about using a crock pot (slow cooker): “Never lift the lid while food is cooking.” Gosh, if you do that, you’ll lower the temperature by 20 degrees F and set your cooking back by half an hour.
I challenge you to find a blog post explaining crock-pot cookery that does not repeat that advice.
To which my response is, so, if I lift the lid ten times in a row, the crock pot should freeze solid? In reality, it takes a crock pot less than 10 seconds to replace the heat lost when somebody lifts the lid. I went through all that in my Post G22-055, Crock-Pot Crackpot.
My point is, I’ve learned to be skeptical, because much of the internet advice I’ve tested has turned out to be dead wrong. Now, when I see practical advice on the internet, I look for some sort of controlled test of that advice, or I test it myself before passing it along.
Penny-wise …
Which brings me to my current, somewhat ridiculous, situation. I’m embarking on a multi-day (possibly multi-week) task to test ways to extend the life of a ten-cent razor blade.
This, because I’m about to buy razor blades for the first time in half a decade. And in doing my research, I ran across lots of free advice on how to make razor blades and disposable razors last longer.
Post 1672 has the full background. Some of the above seems reasonable. Some has a faint odor of bullshit and/or something that mattered back before razor blades were not commonly made of stainless steel.
So, as is my custom, I figured I’d test those before I passed them along, and try to establish the extent to which these practices can extend the usable life of a razor blade.
… Pound Foolish?
The first stumbling block is that I want to test the sharpness of razor blades in some objective fashion. (I.e., other than by shaving with them). And commercial sharpness testers cost hundreds of dollars. Rather a lot to spend to test a ten-cent blade.
I first saw a sharpness tester used on Project Farm. Didn’t seem like there was much to it. You cut through a taut thread/wire with a knife. The thread sits in a holder, on a scale. The scale registers the downward force required to part the thread. The sharper the blade, the less force required.
I believe that much of the expense associated with a commercial sharpness tester is that the thread/wire is exceptionally uniform. It’s calibrated so that the force, in grams, gives you an estimate of sharpness on a well-established scale. So you get a reliable, repeatable, comparable measurement.
By contrast, all I need is a way to compare sharpness across different razor blades. As long as the results are repeatable, and give some indication of relative sharpness, I don’t much care whether or not they can be compared to standard scales of sharpness. I don’t need the precise calibration of a commercial sharpness tester.
Cheap sharpness tester
Materials consist of:
- Big flat washers
- Super glue (NOT hot glue).
- Thread
- A hex nut of a size to match the washers
- A kitchen scale registering in grams.
The idea here is to produce a bunch of washers with a stout thread glued across them, with the thread under the same tension for all the washers. The force required to cut that thread, with various razor blades, should give me some indication of the relative sharpness of the blades.
To achieve that, line up the washers on a table top. Tape the thread to the table top, drape across the washers, and hang it over the table edge, with some weight on it. Put two drops of superglue on each washer to glue the thread in place. Cut them apart when the glue is dry.
(Note that washers have a flat side and a rounded side. For consistency, these all have the rounded sides facing up. By the look of it, I had a heavy hand with the superglue. No harm, I think, just a longer curing time. The hex nut serves as the weight here, and will serve as the “spacer” to give me room to cut the thread, once these are sitting on the kitchen scale.)
The upshot is a home-made mock up of a commercial sharpness tester. I’ve replaced the standardized material with some random thread I happen to own. I’ve replaced the accurate logging scale with my kitchen scale registering in grams.
Alternatives that did not work: I tried hot glue, which sets a lot faster than superglue. But it simply did not work. The thread slipped right through it. I tried using disposable flossers, instead of thread-glued-across-washers, but there seemed to be too much variation in the toughness of the floss across the 4-cent flossers.
So, in the end, the only repeatable approach was to super-glue thread to washers. Which is a drag, unless you have a whole box of washers. Because you only get a few tests at a time.
Surely the weakest link in this setup is that I hold the blade in my hand to test it. For now, that appears to work well enough. But I’m sure I’d reduce the variance of the readings if I had a blade holder that could be slowly pressed into the thread.
Cheap leather strop
No sense stopping there. Now that I can test razor blade sharpness, the first thing I’m going to try is stropping (burnishing, polishing) the razor blade. Will this restore that used blade to the sharpness of a new blade, or not?
It makes sense to start here because I can test it immediately with my supply of used razor blades. (And if it works well, I immediately have a multi-year supply of usable razor blades, because I’ve been tossing my old ones in a “razor blade bank”. And I then have no need to test anything else.)
A traditional razor strop was made of leather, so I made a quick-and-dirty razor strop from a scrap of leather glued to some foam board. I’m not sure if there’s any art to choosing the leather, so if this doesn’t work, I may try a different strop material. But for moving this project forward, that will do for now.
Results 1: Used blades definitely appear worn, under a microscope.
I was surprised to see that even a cheap USB microscope was adequate to show the difference between a new blade (below, left) and a used blade (below right). For the used blade, note the erosion of the blade corner in the first photo, and the generally pitted and uneven razor edge in the remaining photos. Contrast that to the generally straight and uniform edge of the new razor blade.
Results 2: Stropped used blades look better, but lose the double-faceted edge.
Next you see the same two blades, but this time I stropped one edge of the used blade. I ran it “backwards” over a roughly 6″ long piece of leather, 20 times. Then flipped the blade, and ran the other side (of the same edge), ditto. To summarize, it was a well-stropped blade, as these things are reckoned.
Stropping the used blade did two things.
First, stropping removed much of the raggedness of the razor edge that is evident in the un-stropped used blade above. That was actually visible to the naked eye, as the stropped edge appeared to be brightly polished, compared to the un-stropped edge.
But, in addition, stropping seems to have removed or rounded-over much of the secondary facet of the razor edge. Note that the new blade always clearly shows two different angles at the razor edge, with the very tip of the razor edge cut at a slightly steeper angle than the rest. But that feature all-but-disappears in the third photo of the stropped edge. Basically, it has largely been polished away.
Results 3: Stropping appears to have dulled the blade edge a bit.
The data are what they are, and I won’t apologize on their behalf. Except to note that there’s a pretty high variance across trials of the used blades, suggesting that maybe the blade itself is not uniformly sharp after it’s been used.
In any case:
- The new blade gave uniform results, average of 35 grams to cut the thread.
- The used blade was duller, average of 44 grams to cut the thread.
- The stropped used blade was duller still, average of 53 grams to cut the thread.
Results 4: Blind shave test, no discernible impact of stropping.
At this point, I have one used blade that has one original edge, and one stropped edge. I put that in my razor, gave it a few spins, shaved one side of my face with one side of the razor, and the other side with the other.
I could not tell which side had been stropped. And, in fact, when I guessed, I guessed wrong.
So take that FWIW. Possibly, I tossed that used blade before it was really worn out. So I should redo at least this portion after wearing a blade down to the point of painfulness.
Conclusions on stropping to restore used razor blades.
Stropping with a leather strop absolutely does something. It removes much of the raggedness along the edge of the used blade. But it appears to do so at the expense of removing the original two-angle bevel of that edge. And, FWIW, it appears to result in a somewhat duller blade. And, at least for this sample of one blade, I could not tell which edge had been stropped, when I then shaved with that used blade.
Much of this seems consistent with the research done on blade wear at MIT, cited in my prior post. To paraphrase, researchers there found that razor blades didn’t so much get rounded-down as they got beaten-up. The quality of the shave declined over time not because the razor edge rounded over, but because the razor edge accumulated numerous tiny chips and cracks.
If true, then stropping (or polishing or burnishing) didn’t so much sharpen the blade as it removed a lot of the microscopic irregularity along the razor edge.
So, why didn’t stropping the used blade result in a noticeably better shave?
At this point, my bet is that I simply didn’t let that 10-cent razor blade get dull enough for stropping to matter much. I mean, sure, I’m cheap, but I’m not so cheap that I’ll put up with a dull razor blade, when a new one costs about 3 cents a shave.
So, I’m going to try this one more time, after I’ve used a blade to the point where it hurts to shave. At that point, I’ll test the sharpness as I did above, and I’ll see whether or not stropping does enough to reduce the pain from shaving with a dull blade.
More to follow.
