How a razor blade can be damaged as it cuts human hair (2020)
news.mit.edu
news.mit.edu
For me though it didn’t detract too much from the awe. What an incredible result.
The videos are very cool and I appreciate cool videos, but I don't see any evidence in them for the claim of capturing damage to the blades. It's possible that the press release omits clearer videos that unequivocally show damage to the blades during cutting.
s3 is good though. It actually shows some chips.
The site focuses mainly on sharpening razor blades and is full of SEM images of blades in various conditions. Very cool to see.
This page about burrs has some particularly cool images: https://scienceofsharp.com/2015/01/13/what-is-a-burr-part-2/
I'm no knife expert, but my understanding is that today's best knives use VG-10 steel, which is designed to "chip itself to make itself sharper". So its hard, flexible, slightly more brittle than you'd expect. But these micro-chips end up sharpening the blade more often than not. There's more than one way to design a blade's metallurgy.
For shaving steel, it needs to be as cheap and flexible as possible, so that machines can mass produce them. High end knife-blanks cannot be punched if the steel is too hard or strong (leading to a "price cliff", where the best steels are an order of magnitude more expensive than the punchable lower-cost steels).
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So yes, very interesting experiment. But also consider the overall picture: chip-resistance isn't everything.
The amount of steel flaking off a knife into any given meal is likely much smaller than how much iron is in the food on its own merits.
Food prepared in iron cooking pots as an intervention for reducing iron deficiency anaemia in developing countries: a systematic review - https://pubmed.ncbi.nlm.nih.gov/12859709/
It's also something that many vegans have looked into https://plantprosperous.com/cast-iron-cooking-for-vegans/ (which links to the above article too - though I found the nih one first)
My search-fu is failing me at the moment, but that was also believed that this was an important part of the pioneers heading west in the early parts of United States history.
I believe also a little iron fish is sometimes introduced into the non iron pot during cooking.
https://brightthemag.com/lucky-iron-fish-raise-questions-abo... and https://pubmed.ncbi.nlm.nih.gov/28049274/
VG10 just is designed for those chips to sustain the sharpness of the knife, so it requires less sharpening. You can look at the ends of any knife that's been worn away, and its not as smooth as when it was originally sharpened.
The knife's edge is the thinnest part of steel, and may only be a few atoms thick when properly sharpened. It doesn't take much for it to chip off.
"Sharpness" is related to the physical size and radius of curvature of the apex of the blade, combined with the angle of the terminal bevel. [1][2][3]
Chipping of any sort almost certainly tends to erode the sharpness for many reasons, not least of which is that a sharp edge is a very low entropy state (compared to a dulled / chipped / etc edge...).
VG-10 steel is considered "entry level" in terms of high end steels. [4] It was first introduced in production knives in the mid-90s, almost thirty years ago! [5] And there has been significant progress in materials since then.
Almost all mid- and high-end knives these days are cut from blanks via an industrial laser or waterjet cutter.
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[1] https://scienceofsharp.com/2014/01/25/quantifying-sharp/
[2] https://scienceofsharp.com/2014/08/18/definitions-of-sharp-a...
[3] https://scienceofsharp.com/2015/03/24/sharp-and-keen-part-2/
[4] https://www.bladehq.com/cat--Best-Knife-Steel-Guide--3368
That said, a well sharpened kitchen knife should have no problem at all with tomato skins.
I noticed that when I got a new knife recently it didn't feel smooth at all, more like it had lots of microscopic burrs. That knife cut through (thickish garden) tomato skins more readily, even after weeks of knife use. Eventually I had to resharpen that knife and I just find that even though I can get it nice and sharp the type of edge I put on the knife doesn't last as long.
And yes, when I cut a lot of tomatoes I might use a serrated knife but in normal use I don't like to switch so much so I do almost everything with a 8 or 9" chef knife.
I bought a Celestron USB microscope. It was fascinating to look at my skin, nails, desk surface, carpet, anything. Well, at least for the 15 minutes before the device failed. I returned it and never bought a replacement. :-(
Has anyone had luck with a toy-ish microscope in the $200 range?
Would be interested in a recommendation for something with higher magnification
Considering what started the whole idea of the consumables industry, a patent on making razor blades longer-lasting seems incredibly ironic.
That's the real dark side of patent law - its used by the entrenched businesses FROM competitors entering the market with better technology for up to 17y.
That's exactly how we got Reprap so late - Stratasys patented the whole lot of 3d printing tech, and the patent didnt expire until 2011.
What both these studies reveal is an absence of bending of the sharp edge, indicating that the tradition of razor stropping has no real effect.
Indicating that if stropping does help, it's not by the obvious/expected mechanism of bending the sharp edge back.
It's unconventional, but I use an abrasive when stropping my straight razor (quarter micron diamond paste), which greatly increases the sharpening effect and reduces the need for other sharpening (traditionally, honing on stones).
I strop with a fine honing compound on the strop, and the purpose of that for my application is to get a more highly polished edge than I get off of stones. The[0] explanation among woodworkers being that a more polished edge has fewer micro serrations along the edge that create weak points on the edge for dulling to start. If the edge has fine points from coarser (relatively) stones, they can break off, leaving a definitely non-sharp region behind. Or something like that.
Other tools that are frequently stropped include drawknives. Chisels and plane irons are less commonly stropped because the softer strop inevitably reduces the flatness of the blade at the cutting edge[1].
[0] Ok, one explanation. Some woodworkers will argue bitterly about anything related to sharpening.
[1] The importance of which is another topic that woodworkers will argue endlessly.
Extending the life of a razor blade sounds nice, but cutting hair perpendicular to the blade means shaving against the grain, does it not? I don’t want to handle the pain of doing that on the first or second pass while the hair is still long enough (like a couple of millimeters or longer, which cannot be trimmed using a trimmer and needs a blade). But shaving against the grain gives the smoothest skin texture (at the risk of causing ingrown hair, which for me is quite rare).
What I’m saying is that I’d rather the blades dull and need replacement sooner than put up with the burn and pain caused by shaving against the grain from the get go. A few passes with the grain and perpendicular to the grain (sideways) helps the “against the grain pass” be less painful and provide a smoother result.
I’d still love a blade that lasts longer though.
The two biggest things for me were using a shaving oil rather than a cream, and shaving first with the grain and then across.
The latter required more time as my facial hair is very thick and the “direction” seems to change a lot on my face.
I can shave with a dull blade, completely dry, against the grain, in any direction, and it doesn't bother me a bit. Occasionally I'll cut myself and not notice.
(I don't use a dull blade since it's not efficient, but I'll use one if nothing else is available.)
If it is gene based, I'm not sure if it's something that moderates pain tolerance, hair / keratin composition, or some combination. I can grow a really thick beard, fwiw.
They are $10 for 100-blades, extremely cheap, very sharp, very good at cutting. I highly recommend them.
I only shave twice per razor. Some people shave once-per-razor (throwing away a blade each day). Its just 10-cents a blade after all...
That video was oddly pleasant to watch. I admit I was expecting to see the blade become miraculously f'd up in the process, due to the rest of the article, but hair is indeed very soft and the look of that angular cut at such a scale is kind of amazing to think about.
(Perhaps when such microscopes hit Aliexpress we'll see this genre enter the extremely-satisfying-videos arena)
That or scanning electron microscopes have gotten a way faster “shutter speed” since I last looked at them.
https://scienceofsharp.com/2014/08/13/what-does-stropping-do...
https://imustacheyoutoshave.com/sharpening-a-razor-with-your...
I just switched to a double edge safety razor and never looked back.
Why shaving dulls even the sharpest of razors - https://news.ycombinator.com/item?id=24075855 - Aug 2020 (123 comments)
Firstly, I'd read that DE blades actually get sharper after the first shave, due to coating wearing off, then quickly dull after the third or fourth shave. Personally, I'm unsure of this finding, as I always find new blades the best cutting and in fact change my blade every other shave.
Secondly, it's commonplace to the point of common knowledge or folk lore that it is rusting that ruins blades, hence you should soak them in alcohol, or dry them vigorously after each shave. Is this even true?
As for changing every other shave, I guess it depends on beard and razor. I have a Merkur 34C that tugs like mad whatever blade I use, new, old, in-between, they're all as bad. And an Ikon slant thing that feels like you could use a piece of paper in it and it'd work wonderfully. I go about 60-70 shaves before I can tell the razor might be getting a bit dull in that one.
With a new blade, it feels like rubbing a wand on my face. By the 4th shave, it feels like a tiny metal man is plucking each hair from my face. Especially painful in the mustache area.
Skin oils might be a bit of harm, too.
Razors have a much, much tinier edge than even the sharpest filet knife. So basically every cut deforms the edge in someway.
They could potentially make thicker blades, but most people aren't going to ever bother resharpening them, nor would they be able to get the edge correct. And if they make the edge itself thicker... it's going to feel like shaving with an axe.
https://knifesteelnerds.com/2018/06/18/maximizing-edge-reten...
if you shave along the direction of hair growth, the blade will approach hair at 15-30 degrees which causes excess wear & tear on a shaving blade.
if blade is not extra sharp, blade starts ripping hair, shaving along the grain in comparison is more forgiving for duller blades.
Given that the angle of cut matters is it better to shave certain parts of the face with the grain or against?
what really kills the blade and creates cracks is when you cut hair at 15-20 degrees and blade cuts hair and then starts dragging it along your face while cutting and this is how microcracks form and grow in size.
you can create your own experiment with knife and some veggie like green onion. try to cut it at steep angle and drag it along the cutting board - and you will see that it produces much more stress on cutting surface
Item 2. In a somewhat oblique vein, during COVID I always wore N95/P2 masks in public and I always took extra heed to follow the instructions that came with them which read to the effect that 'this mask will be less effective on those with bearded faces'.
Clearly that stands to reason so the question is by how much.
I'm constantly bemused by the large percentage masks on bearded faces and whose wearers seem oblivious to the fact that their beards are likely rendering their masks ineffective. Especially so when I see doctors on TV who've beards and who are there specifically to proselytize the virtues of wearing masks. With their beards popping out from behind their ill-fitting masks, it seems strange to me that these highly trained medicos seem oblivious to the obvious fact that their beards are putting them at risk—not to mention that they are setting a bad example.
Now the issue is this: given that a clean-shaven, stubble-free face provides a better mask-to-skin seal than one with stubble, the questions are:
Does anyone know of whether tests have been done on N95-type masks to test the effectiveness of their mask-to-skin seals? If so, whether any significant leakage was detected at the seal and whether stubble growth throughout the day worsened said leakage (the implication being that by the afternoon/evening masks would be less effective though increasing seal leakage)?
The corollary of the question would be to ask if a beard stubble impedes the effectiveness of the mask-to-skin seal then at what point in the growth of a newly-forming beard (at what stubble length, etc.) does the stubble render the mask ineffective (dangerous to wear)?
I suppose, given all the fuss over COVID, I've been rather surprised by casualness over the approach to mask-wearing given that the warning were there on mask packets before the pandemic. I would have thought this would have alerted many to the fact come COVID but seemingly not.
BTW, my attention to detail seems to have paid off so far (I've not caught the disease as yet). Nevertheless, it would have been good to have been able to put some some figures to the practice rather than working anecdotally.
I think you're looking for the book "Knife Deburring: Science behind the lasting razor edge" by Vadim Kralchuk. The author had a good website, but it appears no more and my cursory web search indicates that he has passed away. He has / had a YouTube channel as well.
I'm not bad at sharpening plane irons and when I set my mind to it I can make them razor sharp—certainly sharp enough to shave with but I only test them by shaving the hairs on my arm and they do that very well.
That said, most books on this subject only cover techniques and not the underlying metallurgy. The metallurgy is important but the problem that most of us encounter is that we plane users don't know what it is (as it's usually unspecified).
Even if it is, it doesn't help much. Leaving aside badly-tempered steel (sharpened to red heat on a grinder etc.), some steels are just horrible to work with, I've some block plane blades made in the 1930s that have high tungsten content and they're almost impossible to sharpen well and even when razor sharp they don't cut well and it's never been clear why. Thus my comment about wanting to know more about the subject.
Excellent (aftermarket) plane irons of known alloy are widely available (at least here in the U.S.). I know some woodworkers value having all original parts, but if the primary goal is paper-thin even-width shavings it's hard to beat modern metallurgy.
Some steels are just horrible and tempering and hardness are not necessarily good indicators of quality. I have a few chisels that superficially seem OK and the steel is hard and takes a good edge but five minutes later they're useless, others, sometimes even cheaper ones, turn out to be excellent.
As a techie who like playing with tech toys I thought of using a handheld x-ray fluorescence spectrometers like, say, this one: https://alloytester.com/xrf-steel-tester. There are any number of them around these days but they're expensive even to hire and I can't really justify one just to indulge my curiosity. However though, it would be really nice to go around testing everything that has an edge and logging its alloy properties against actual performance tests. Perhaps some day.
I couldn't care less about original parts (they're tools!)—so long as the tool works well (I don't for a moment consider myself a collector of old tools). That said, when making repairs I'll go to some trouble with old tools to match a tool with its 'correct' parts if possible (but ultimately it's a pragmatic decision—if I don't have the correct part I'll use wherever is to hand or what works best). By that I mean if it's possible to mate together a tool with parts from the same manufacturing source and same era then I'll do. For example, my No. 8 Stanley somehow lost it's lever cap during a move and I had access to several others that would fit but I selected one that came from the same factory and manufactured around the same time (in this instance the plane was of US manufacture/New Britain and made in 1933, so it received another lever cap from the same factory made in the same era (it was of the first generation to use the kidney-shaped slot for the cap's screw). I'm in Australia, so I had lever caps manufactured in the US, UK and here (including UK Record parts) to choose from. Nevertheless, it now has a plane iron of modern manufacture (but I've kept the original one and it's identified as belonging to said plane). There's also another reason to match parts which is that they usually fit better (leaving Bed Rock planes aside, I'm also of the opinion that the best consistent run of 'normal production' planes Stanley ever made came from its US plant and were manufactured between 1933 and about 1941 (the run came to an end when war regulations kiboshed the quality).
I do have a sense of history when it comes to these old hand-tools, my No. 8 is now 89 years old but it's not the oldest, that accolade goes to my No. 45† which dates from 1907. I'm of the opinion that we never actually own these objects, we're just their custodians for life—after all, my No. 8 is still in excellent condition (so are several others which are older), and if looked after with a little care, it'll still have several human lifetimes left in it after I'm gone. BTW, its original owner wrote his name on a piece of paper and dated it then put it in the space under the plane's tote (I'm now very curious to know who he was but I've really no idea). Anyway, that piece of paper stays with the plane (I've really no right to remove it).
Incidentally, I have a copy of Antique & Collectable Stanley Tools - A Guide to Identity & Value - 1996 edition by John Walker. You're likely already aware of it but in case you're not, it's an absolutely invaluable 880-plus page tome on the subject of Stanley tools, there's nothing else its equal. It's the ultimate bible for not only collectors but also for anyone who fixes or refurbishes these tools. There's a new edition out which I've not yet seen (it was out of print for quite some years which made secondhand copies of it much more valuable than many of the tools mentioned therein).
Back to plane irons, I use this mob from time to time for replacement irons but they're expensive here where I live. They are reasonably consistent and work reasonably well but I'm not altogether totally happy with them (it's what I now use in the No. 8, No. 4, 5 etc.): https://www.ibctools.ca/product-category/ibc-blades/. They'll also do paper-thin shavings but that's usually of secondary importance—for me, a steel that keeps a keen edge for the longest duration ranks first (these come close but I've had irons that cut somewhat better).
Thanks for your comment.
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† Damn monstrosity of a thing it is, the only thing I can imagine that's worse would be a No. 55.
Am I the only one who finds the repeated incorrect spelling of "heterogeneous" annoying?
The worst part is, the way they spell it, "heterogenous", actually means something else. Just not what they think it means...
It seems that microscopically, the honed edge of the blade looks like a comb of teeth. When you shave, these teeth fold over. Stropping apparently straightens out the folded edge.
Eventually these teeth break off, and the edge has to be remade. That can be done with a few strokes on a coticule, every 6 months or so.
The authors apparently experimented on stainless steel blades; stright razors are made from carbon steel, which doubtless has a different microcrystalline structure.
[I know, the article's about disposable razors]
Yet one must still sharpen the edge eventually.
This team is playing with fire and should tread carefully. If they should happen to stumble across the secret to a “perma-sharp” razor blade that never needs replacing, I have no doubt that “big razor” will dispatch them with a vengeance.
The team lead will be strolling through the park on a lazy Sunday afternoon, when a stunningly beautiful female jogger “accidentally” steps on his foot. He’ll think nothing of it, but what he won’t realize is that he was just on the receiving end of a Polonium 238 injection delivered at the order of the Gillette family.
Growth, removal, color…
You’d think the richest people would want to invest in that research as they grow older.
We have hair transplants, not really a new thig.
For some woman washing hair is a hours long procedure applying various chemicals :)
Coloring is also "solved" a long time ago.
What do you miss?
"They found that the simulations predicted failure under three conditions: when the blade approached the hair at an angle, when the blade’s steel was heterogenous in composition, and when the edge of a hair strand met the blade at a weak point in its heterogenous structure."
"Tasan says these conditions illustrate a mechanism known as stress intensification, in which the effect of a stress applied to a material is intensified if the material’s structure has microcracks. Once an initial microcrack forms, the material’s heterogeneous structure enabled these cracks to easily grow to chips."
2) I'm not certain, but I presume the idea is that many clickbait article titles are improved by removing the "how".
So why are there no ceramic blade razors?
Perhaps Gillette could put out one of their fancy twenty-odd blade monstrosities with an extra ceramic blade in front though. I'm sure that's marketable to people who haven't figured out they're spending way too much money on something that costs a fraction if you look beyond the products pharmacies push in your face.
I don't doubt that in your experience ceramic knives cut food better than metal ones, but I suspect you have not used a well-sharpened knife. Mass-produced knives are typically sharpened using belt grinders and do not cut as effectively as knives hand-sharpened by someone skilled at it.
Inflation certainly seems like a good motivator for more people to switch to safety blades — wet shaving should be cheap, and it is if one stops buying the stuff marketed the hardest.