Why shaving dulls even the sharpest of razors

https://news.mit.edu/2020/why-shaving-dulls-razors-0806

by WalterSobchak • 6 years ago

136 123 6 years ago

news.mit.edu

yumraj3• 6 years ago

“We’ve learned how to make better blades, and now we want to do it.”

Unfortunately this is at odds with the interests of blade manufacturers, so I doubt we’ll see better blades anytime soon - at least from the current manufacturers.

rgoulter2• 6 years ago

Cartridge razors would surely make more money than safety razors, but people are still able to buy the latter.

As far as I understand the variety of safety razor blades, there's not a race to the bottom where the more-expensive blades don't sell.

Insofar as shaving can be a luxury activity, I think it's possible there's room for more higher price for more durable blades for safety razors.

e.g. The bestsellers here https://www.amazon.com/Best-Sellers-Beauty-Mens-Replacement-... lists a pack of 8 refills for cartridge razors for 24 USD. Searching for "safety razor blades" shows a pack of 100 for 7 USD - 11 USD, and I see a 50 pack for 15 USD.

Semaphor4• 6 years ago

Searching for "safety razor blades" shows a pack of 100 for 7 USD - 11 USD, and I see a 50 pack for 15 USD

I once got the Derby blades [0], $5.59 for 100. I still have around 90 of them left somewhere in the attic because I got what I paid for. Now, I use Feather blades, about the same price for only 10, but one blade lasts me multiple month and I get better results. But as you said, with safety razor blades you only pay a fraction compared to cartridges anyway ;)

[0] https://www.amazon.de/Shaving-Factory-Derby-Professional-Ras...

delecti• 6 years ago

Game theory. If a smaller name starts using those techniques to gain market share then the others will have to as well.

aaron6953• 6 years ago

Men hate shopping, men love tech, male shaving blades are really light so could be posted from one location to the world.

If this works well it would take off for the male shaving market alone, could we skip big corps are evil this time?

Even if it's a 10% improvement, it's not the Neuromancer future we were promised but someone will license it and raise prices by 10% just for the novelty.

anitil• 6 years ago

Huh, I always thought that it was oxidation from getting wet that damaged the blade. I even remember getting a recommendation to clean the blade with alcohol to dry it of faster.

I always find myself falling for this sort of 'Well of course the answer is <simplified answer that is wrong>'

Edit: I've posted to /r/ImageStabilization/ for that first image - https://www.reddit.com/r/ImageStabilization/comments/i54p9s/...

aaron6953• 6 years ago

I palm strop my safety razor, the idea is to smooth the microscopic bumps. No idea if it's scientific.

https://www.bruceonshaving.com/2010/11/17/palm-stropping-raz...

[edit] Sorry, as Someone1234 points out I actually meant cartridge razor

gpsx• 6 years ago

Cooks use a knife straightener on their knives to keep them sharp longer. Well, I'm not a cook, but I do it too. It works really well. I was wondering if people could do this on razors. I think this is equivalent to palm stropping. For a cartridge, I think something with small metal teeth, at the right angle, ran back and forth over the blades, would do a good job of straightening the edges.

xmprt• 6 years ago

When manufacturers make more money by selling more blades, I don't think they're going to invest much into this technology anytime soon.

badrabbit• 6 years ago

DIY blades would be cool though. I can imagine a small company selling long lived blades for a high price.

jayd16• 6 years ago

They'll just start marketing the gel strips more heavily.

keenmaster• 6 years ago

Unlike with mature tech platforms, successful entry into the market is not exceedingly difficult. A new company can offer everlasting razors. Then cleaning cartridges and other refills will become the new razors.

jl2718• 6 years ago

I assume they mean crystalline domain heterogeneity. The best metals are single-domain so that there are no fissures along the boundaries. But that takes very pure material and very slow cooling. A good alternative is nanacrystalline or amorphous domains, which are fairly simple, just blast with microwave energy during cooling. This can make a very strong metal with great working properties, a bit softer, but doesn’t fracture.

dzonga• 6 years ago

before gillete started to market multi-use, multi-blade razors. most folks, like me who have course curly hair would've only used disposable blades only once. n I find, single blade razors to be effective, no razor bumps etc. just wet with water, a light moisturizing oil such as almond n you're done.

news_to_me• 6 years ago

If you like single-blade disposable razors, you'll love a safety razor ;)

FridgeSeal• 6 years ago

I’ve been meaning to buy a decent safety razor setup for a while-any suggestions for brands or models?

ghaff2• 6 years ago

I had always assumed based on what I’d heard that corrosion was the main factor in blades wearing out. Which may still be the case. But this suggests that there are still ways that soft materials can still chip very thin cutting surfaces.

unclebucknasty• 6 years ago

Years ago there was some product, essentially a goo, that claimed to dramatically extend the life of blades. The rationale was that hair was too soft to dull a blade, and what was really dulling them was oxidation.

Don't know what became of the product, but would be interesting to know if corrosion plays a role in the chipping.

ghaff2• 6 years ago

I vaguely remember way back when I was a Masters engineering grad student, one of the undergrads had a senior project that involved dipping razors in alcohol and it significantly increased their lifespan because of reduced corrosion. And that does seem to be a thing according to the Internet: https://macgyverisms.wonderhowto.com/how-to/extend-life-your....

Doesn't mean you can't still chip thin edges of a (presumably) fairly brittler steel blade with something relatively soft of course.

wrycoder2• 6 years ago

Research probably funded with government grant.

They patent it, either start a company or collect royalties. MIT takes a cut. Standard MIT practice.

Qahlel• 6 years ago

They patent it, sell it to Gilette and we never ever hear of this tech again.

s1artibartfast2• 6 years ago

and everybody benefits.

wrycoder2• 6 years ago

Not if you’re a taxpayer that would rather not fund such things.

In other words, the government grant should at least be refunded from the profits.

m3kw9• 6 years ago

The videos in there are oddly satisfying.

taeric• 6 years ago

And yet I've been on the same razor for well over a year. Can't help but think I'm doing something terrible wrong. :(

rtx• 6 years ago

Yes, try a new one you will feel the difference.

throwaway57522• 6 years ago

Same here. I use them dozens/hundreds of times. Maybe our facial hair is softer or we aren't discriminating enough! I notice the difference with a new blade, but it doesn't bother me.

travisjungroth• 6 years ago

Yeah, it comes down to hair and skin. I have coarse hair and soft skin. I wear out razors quickly and it becomes very noticeable.

ComputerGuru2• 6 years ago

I think it's a structural difference in the hair itself, along the difference between diamonds and carbon. I have facial hair that is prone to fracturing and then giving me splinters that can easily go a few mm deep into my fingers.

aidenn02• 6 years ago

For me after about a dozen shaves the razor starts plucking the hairs out rather than cutting them, which both hurts more and leads to ingrown hairs.

caseymarquis• 6 years ago

I've heard a second hand story about some titanium razors made internally at <large razor company> which were given out to employees as gifts. They lasted for years, but could never be released as they simply wouldn't be able to turn a profit.

nordsieck4• 6 years ago

I've heard a second hand story about some titanium razors made internally at <large razor company> which were given out to employees as gifts. They lasted for years, but could never be released as they simply wouldn't be able to turn a profit.

That seems unlikely to me.

Properly heat treated steel is considerably harder than titanium. This is why titanium knife blades are generally limited to niche applications (like dive knives, although that market is being contested by modern rust-proof steels like H1).

Material hardness is one of the leading factors in edge retention.

sliken• 6 years ago

But hair is so soft compared to titanium, seems possible that the much greater flexibility might make up for the poorer edge retention.

throwaway57522• 6 years ago

Seems like a thread where people might be interested in https://knifesteelnerds.com/, which has made the front page on HN on a couple of occasions. I have no relationship of any kind, beyond finding it interesting.

1vuio0pswjnm72• 6 years ago

"When the hair was free to bend, however, chips were more likely to occur. These chips most commonly formed in places where the blade edge met the sides of the hair strands."

So the question is, in shaving, how do we ensure that all hairs are perpendicular to the blade edge and not free to bend?

I use Feather blades exclusively; the number of shaves I can get from one blade varies according to the shaving soap used.

Semaphor4• 6 years ago

Feather blades are great, but for anyone reading this who thinks about switching to a safety razor from cartridges or electrical ones: Don’t start out with them, they are really unforgiving even for safety razor standards in how easy it is to cut yourself.

wolfgang42• 6 years ago

When I switched to a safety razor I bought a sampler pack of different brands of blades. The Feather blades felt great; there was no grabbing or skipping, I’d just glide the razor across and all the hair would be gone. Then I’d look in the mirror and there’d be blood dripping down my neck. They are so sharp that I wouldn’t feel it at all.

Polylactic_acid3• 6 years ago

I started with feather blades. Cut myself a bunch the first few times. It doesn't really hurt but its just annoying because you don't want blood on your clothes. Eventually looked up a guide and found out I was doing it wrong and now I basically never have issues.

1vuio0pswjnm72• 6 years ago

I also use a Muhle R41. I have used this since the beginning and never had any problems with cuts. I did have to experiment with a few soaps find the right one to get more mileage out of the blades though.

natmaka• 6 years ago

Isn't strain-hardening also a factor?

tyingq• 6 years ago

I does ring true that there's little financial incentive to create long lasting blades.

Even if you produce something that's cheaper over a year, I doubt there are many takers for the high up front cost.

opwieurposiu3• 6 years ago

Cartridge razors are garbage, but they are idiot-proof. I use a straight razor (cuthroat) and hone it a few strokes with 8k diamond after every use, no leather strop. Even with the time spent sharpening it is faster than a cartridge razor because it cuts a wider swath and never clogs. It took me quite a few iterations to find a razor/sharpening tool combo that worked properly. A safety razor works almost as well with no fuss sharpening. The other downside of a straight razor is if you drop it could cut your d* off so I always put on shorts before shaving.

catalogia• 6 years ago

I like the middle-ground; safety razors. They're exceptionally cheap and idiot proof. Mine really doesn't clog like cartridge razors either. Cartridge razors seem like a scam in nearly all respects, although I concede loading them is probably safer for the elderly or generally those with dexterity problems.

vl• 6 years ago

Safety razor requires more time to shave than cartridge razor because it requires more strokes. But I actually prefer it because usually I don’t shave every day. Cartridge razor clogs up in this case. When I shave every day I use either cartridge razor (Dorco) or wet electrical (Braun 9000). Both work greatly for daily shaving, fail for shaving every few days.

Fezzik2• 6 years ago

Also: entirely recyclable.

evanelias2• 6 years ago

Another nice middle-ground is a shavette, which is a disposable blade straight razor, like what barbers use. Although it definitely requires a lot more care/practice than a safety razor initially, you can get a really close shave once you get used to it.

Shavettes are extremely affordable, like $10 for the base. Unlike a "real" straight razor, shavettes never require sharpening since they just use standard disposable single-edge blades, or a double-edge blade split in half.

speakspokespok• 6 years ago

Switched to a safety razor (Also called a Double Edge) after Mach3s had been out for awhile and they started jacking up the price. That must have been 2005ish and I've not really used anything else since. For quality of shave there is no comparison. Badger & Blade forum had a good process at the time where you started with a certain blade and worked up the sharpness ladder as your skin toughened up and you found the blade/razor combo that worked best for you. I'm a Personna Prep and Merkur 34C guy myself.

Shaving with a double edge instead of using a disposable is comparable to preparing your own dinner rather than going to McDonald's. It's a skill, it takes time, it's far for economical, there's a ritual to it, and it's enjoyable. It's also a uniquely positive masculine thing (and I think that that does matter) and one day I can pass the razor to my son or grandson.

Merkur 5C

kqr2• 6 years ago

I switched to safety razors because the place where I used to get my straight razor sharpened stopped accepting orders from regular people.

If someone knows someone in Sweden who will do a good job of making my straight razor... well, razor sharp, I'm all ears.

opwieurposiu3• 6 years ago

This is the stone I am currently using, 8k(3 micron) diamond. Made by sprinkling diamond dust on a steel block while electroplating the steel with nickel. The nickel holds the diamonds on pretty firmly so it lasts a long time if you do not abuse it. Cost about $80 https://www.sharpeningsupplies.com/8-Extra-Extra-Fine-Diamon...

In the past I have used fiber optic polishing film, it works and cost around $1 a sheet. It must be stuck to a very flat surface like a glass table or your bathroom mirror. You want something in the range of 1-10 micron.

https://www.ebay.com/itm/114106443536

esaym• 6 years ago

I think the trick with straight razors is to finish the blade with a denim strop with abrasive compound. I only have two stones, a 2k and a 5k. From there, I strop with a strip of denim that I put a little bit of automotive "swirl remover" (it's like car wax with a bit of abrasive in it, but the point is almost any kind of "polish" compound will work.)

This blog describes why denim works so well: https://scienceofsharp.com/2016/04/14/simple-straight-razor-...

subhro2• 6 years ago

I sharpen my straight razor at home. Get a 3K, 5K, 8K and maybe a 12K naniwa superstone. Unless you massively damage your razor somehow, You would be good for life.

stormdennis• 6 years ago

How many toes, you got?

opwieurposiu3• 6 years ago

I got plenty of toes, but only one d*. Toes are expendable.

this_is_not_you2• 6 years ago

I have been using a safety razor for shaving my face for a few years, now I just have a beard and don't shave anymore apart from shaping the beard.

But I do have to shave my head and I just can't figure out how to use a safety razor or straight razor for that. I keep cutting myself. The margins seems to be quite narrow and boy does your head bleed if you cut it...so I am stuck with cartridge razors which actually works really well. Just means spending more money and dealing with clogging.

nelaboras• 6 years ago

I am using a safety razor for my head. Once every 2-3 shaves I cut myself (usually on my non-handed side) but otherwise no issues. The cut usually heals by the time I'm done and I have rather thin/sensitive skin.

Derby or Feather blades and a cheap €15 handle. I try to shave once with the grain, once sideways. The blade is held at quite am angle but with very little pressure.

raxxorrax• 6 years ago

I used a "cutthroat" razor after being sick of others getting dull that quickly. With changeable blades though. They are always in pristine condition and my barber said it is better for most people. 100 pieces à 5$...

But even with a good brush, which is as essential as a sharp blade for that kind of shaving, it just cannot compete in my opinion. It takes longer and is more bloody. Boy did razors made technological improvements, I think the plastic ones really can compete today.

It looks easy how barbers do it but it is another thing if you do it in front of a mirror.

nordsieck4• 6 years ago

1. I'm not super familiar with razors, but I am pretty familiar with knives. The chipping they describe is typical of a knife that is ground with an angle that is too acute. In knives made of hard material they fail by chipping, whereas in knives with a softer edge (think German kitchen knives) the edge rolls instead.

The classic solution to this problem is to grind the secondary bevel more obtusely so that there is more material to "support" the edge. This results in a knife that is less sharp, but more durable. That may be a tradeoff that razor manufacturers are not willing to make.

2. There are already steel making processes that are designed to make more homogenous steel. The most famous one is probably CPM (Crucible Particle Metallurgy):

Instead of pouring an ingot (where the additives have a chance to settle into a non-homogenous state, they basically pour the steel through something similar to a shot tower - making lots of tiny homogenous micro-ingots that they later fuse together in what is essentially a sintering process. The end result is a much more homogenous ingot. Practical testing shows that steel made in this way is more performant, although it presumably increases the manufacturing cost.

zerocrates• 6 years ago

"Less sharp, more durable" sounds like it's pretty much all downside if you're in the business of selling razor blades.

mturmon• 6 years ago

The CPM process you describe sounds similar to so-called PMV-11 steel, which is used in some high-end chisels and woodworking planes. It’s not just marketing, several professionals who are mostly impartial have said its noticeably better than conventional tool steels.

There are some nice wear images off the site below as well.

http://www.pm-v11.com/Story.aspx

ComputerGuru2• 6 years ago

Thanks for the link! The images are on these pages:

Impact testing: http://www.pm-v11.com/TestingImpact.aspx

Wear testing: http://www.pm-v11.com/TestingWear.aspx

Sharpening: http://www.pm-v11.com/TestingSharpening.aspx

nordsieck4• 6 years ago

Not to derail the conversation, but I spent some time reading about PM-V11. Is there a data sheet somewhere? It looks to me like a mystery steel, which I'm always pretty skeptical of.

Specifically: while it's very hard to make a particular steel perform better, it's very easy to make a particular steel perform more poorly. I'm not claiming that they purposefully engaged in malfeasance, I'm just generally skeptical.

I'm particularly skeptical of their claim that it outperforms CPM-M4, which is generally used for bladesports[1] for its ability to take a fine edge and resist mechanical edge deformation. I'm not surprised by the difficulty they had in sharpening it, though.

___

1. https://www.youtube.com/watch?v=YkemT5ciBnw

Polylactic_acid3• 6 years ago

That may be a tradeoff that razor manufacturers are not willing to make.

Razors are so cheap ($0.10 each) that there is simply no reason to make them worse in order to last longer when virtually everyone would rather they work as well as possible and spend another 10 cents a week.

nattmat• 6 years ago

Where I’m from Gillette is the popular brand, and they are $5 to $7 each.

m4633• 6 years ago

Unless you are buying gillette blades. Even at costco you can spend almost $50 on a bunch of refills.

Unfortunately I seem to have the best shaving experience with gillette blades. I tried Harry's and other brands, but then I tried gillette again and it was markedly better.

55555• 6 years ago

But would they make more or less money if their blades lasted longer?

tus88• 6 years ago

I would like to know this too.

known• 6 years ago

Pythagoras theorem in play;

peterwwillis• 6 years ago

I have used straight razors, safety razors, electric razors, and various cartridges. A good multi-blade cartridge is vastly superior to anything the layman can do with the first three. They shave all kinds of growth in one pass, don't cut you, and get very close, without needing any foam. They really are the pinnacle of shaving technology. It's amazing how people ignore them for older tech which can only match them with a lot of extra work.

Semaphor4• 6 years ago

It's amazing how people ignore them for older tech which can only match them with a lot of extra work.

a) Price. You save a huge amount of money over time.

b) Ritual. I really enjoy whipping up the soap with my brush, and lathering up my face before shaving with my safety razor.

c) Efficiency. If you don’t shave every day (I sometimes don’t for up to a week), cartridges get clogged way too quickly with thicker hair while my safety razor can easily handle it.

evanelias2• 6 years ago

If you have especially curly facial hair, multi-blade razors have a tendency to yank out some hairs instead of cutting them, especially in places where some hairs grow in a different direction. This in turn causes irritation, razor bumps, ingrown hairs, etc.

After using multi-blade cartridges my entire adult life, I switched to a shavette (disposable blade straight razor) a few months ago and it pretty much immediately solved all of the skin irritation issues. Plus it's massively less expensive. The downsides are it's slower and more injury-prone, admittedly.

growlist3• 6 years ago

Idk. I switched to a safety razor and everything is better now, save for slightly worse nicks, but a shaving block takes care of that. And the cost of a cartridge (couple of quid each?) certainly is NOT better than the cost of a fresh blade in a straight razor (25p or so).

Edit: old style i.e. safety razor, soap and brush is also far more environmentally friendly than new style i.e. cartridges plus foam out of a can.

Markoff• 6 years ago

Looking at the first photo - aren't you supposed to shave against the growth of hair?

I use hair clippers, clean shaving is for babies.

m4633• 6 years ago

I shave with the hair at first, then against it.

ajuc• 6 years ago

Not "even the sharpest" but "especially the sharpest". The sharper the edge the easier it is damaged.

Also - I've got a cheap beard trimming machine I bought 10 years ago. I use it every week or two, and I haven't replaced the blades even once (I don't think it's even replacable) - still works fine.

It seems the solution is to use blades that are almost dull?

fho• 6 years ago

Definitely not an expert here but I think the difference is that trimming machines "cut" by pinching the hair between two moving surfaces. That way you can have a 90 degree angle at the cutting edge that is much sturdier than a blade that is designed to cut.

JeremyNT• 6 years ago

This is my understanding as well.

I've tried every form of razor and - despite all the folklore - the best[0] shaves for me are to be had by electric shavers, which operate on this principal. These have a foil which the hair can protrude past, then it is sheered off by either rotating or oscilating "blades" that push the hair against the foil.

It's like a pair of scissors, which can operate when "dull" - because there's something to push against, they don't need to be nearly as sharp.

[0] "best" meaning a combination of least discomfort, time efficiency, and closeness - a safety razor against the grain can get closer, but it's a miserable experience

ggm• 6 years ago

"I liked the scanning tunneling microscope so much.. I bought the company"

hendry• 6 years ago

Water dulls blades in my experience.

You need to ensure they are dried well after use, otherwise they dull far quicker. I have no idea why, so perhaps someone can test my hypothesis?

nordsieck4• 6 years ago

Water dulls blades in my experience.

I've heard that corrosion can be particularly damaging to the very edge of blades. The idea is basically that all corrosion is generally limited to small surface patches (in the presence of good maintenance) however, the very edge of the blade has a very high surface area to mass ratio, so corrosion affects the edge more than anywhere else.

I'd expect any razor that is designed to be around water to be of stainless steel or some other corrosion resistant material, but I suppose it's possible that corrosion happens on the edge anyhow (albeit at a much slower rate).

lmilcin• 6 years ago

Not just human hair. I use razors to scar bread loves before baking them. Surprisingly, the razors get dull quite quickly after couple dozen loves.

tcpekin• 6 years ago

Here is the actual article, with much more analysis:

https://science.sciencemag.org/content/369/6504/689

growlist3• 6 years ago

Wow, amazing imagery. Personally I switched to straight razors recently and given the very low cost of blades I'm quite happy to use a new one every couple of shaves, which for me is only once a week.

Edit: sorry, I meant safety razor, not straight.

Solstinox• 6 years ago

You mean double-edge, right? I thought straight edge was basically a shaving knife you can sharpen...

growlist3• 6 years ago

thanks, edited my comment

aidenn02• 6 years ago

I wonder if powder metallurgy blades last longer considering they tend to make more homogeneous alloys

Why shaving dulls even the sharpest of razors

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