electron microscope study of feather blades

Apologies if I missed an existing thread on this.

http://sharpologist.com/2011/12/the-experiments-analysis.html has put up a link to http://www.reddit.com/r/asksciencef...itative_analysis_of_the_edge_characteristics/ - original PDF via https://docs.google.com/viewer?a=v&...yNTQ2ZWMtYWIxOC00ZDI2LTkzYjQtMjI5NzEyYTVmYjE3

The author shaved with several feather blades, and examined them under a scanning electron microscope. He also did some composition analysis of the steel. I will just quote the conclusions, but follow the links above for pictures.

It has been qualitatively shown that the edge characteristics of stainless steel razor blades edges deteriorate over continued use. This deterioration is a function of the number of shaves, not a function of corrosion due to humidity. Grains on the faces of either side of the bevel are shown to pull out with continued use, leaving behind a textured surface that might be responsible for nicks and cuts. Portions of the very tip are also fractured off as seen from the side profile view which may also lead to nicks and cuts. The edge tip radius of the razor blade has also been shown to increase with continued use, which will hinder the ability of the razor blade to shear through whiskers given the greater surface area. The razor blades were likely sputtered with a very thin layer of Pt only for protection of the blade during the shelf life, or possibly marketing. It should be stated that this experiment has a very small sample size of razor blades, and all of the shaving was performed by one individual. Any inconsistencies with the experimenter would lead to inaccurate results. More testing shaves would be needed with various razor blades, performed by various people, in order to get better quantitative results.

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As the author says, more study is needed. But to me this suggests a few theories about palm-stropping and corking. I suggest that palm-stropping or corking before the first shave probably will remove blade coatings - which might help if a given person finds the coating irritating. After the first shave, palm-stropping probably does not unroll the edge - for the simple reason that these photos show no evidence of edge rolling in the first place. Nevertheless it may help extend blade life marginally, but by polishing the bevel and removing foreign matter rather than unrolling the blade edge. As usual for blade life extension techniques, though, this is not important unless it happens to make a practical difference in blade life. For example, stretching a blade from 2.75 shaves to 2.8 shaves is pointless. Stretching a blade from 3.9 to 4.1 shaves might be worthwhile.

I also wonder if alcohol, acetone, or scrubbing bubbles might remove some of the foreign matter that the author found on his blades? If so, that might explain why those techniques also extend blade life for some folks.

Those pictures just confuse me more than ever.

According to that article, the chunkiness on the bevel is debris from grinding and plastic deformation. Clearly we shave differently because only 20% of it disappears on each of my shaves. This explanation certainly explains why a clean, smooth surface appears wherever a chunk breaks off. I always thought that chunkiness was a thicker (200-350nm) sprayed on coating of chromium on the bevel. Forget about the platinum coating--no chance of seeing that at 5-10nm, and it's not shown in the electron microscope pictures either. I'll venture to guess that the general lumpiness across the entire blade surface comes from the texture of the rollers when cold rolling.

It's definitely hard to see certain types of details in those pictures. I'm really surprised to see the same old optical problems: depth & angles, lighting & shadows, and contrast are all evident, made more difficult by the large depth of field. It's hard to tell in the six comparison shots which pass is rougher or smoother.

See my feather blade pictures new and old to see what I'm talking about.

Thanks for the links, Steve. I do not frequent the darkroom, so they are new to me.

Did you ever look into the effects of palm stropping or corking?

No. I've been working on getting a better system that's faster to set up and more repeatable. Got some better Nikon optics, a better camera, and am trying to build a macro system instead of using the microscope, but putting the right parts together is a bit daunting. Just to show how incredibly frustrating it can be, I have a set of eyepieces in a molded case, but can't figure out how to open the case. I'm tempted to just start using hammers and epoxy.

Wow, that's really cool. I've always wanted to look at a razor's edge through an electron microscope. It's really amazing to me to watch the progression from brand new to used and all the assorted material on the blade.

Nice article, but I'll still let me face tell me when to ditch a blade.

I've never found palm stropping to do anything useful at all. That's an interesting study which seems to confirm what I've always suspected and experience seems to prove, the actual shaving action is what ruins the blade edge, not moisture. At least not on stainless steel. Carbon steel is clearly a different animal. Obviously those will rust if left wet even for a short period.

I once stumbled upon an engineer's forum where the participants were discussing how to prolong blade life for their razors. One of them had the patience to actually wet and let air dry a blade for about 30 wet and dry cycles (as I recall this took him about 15 days using two cycles each day) without shaving with it and noted that when the blade was finally put to use it shaved like it was brand new. Corrosion played no part at all the blade dulling.

Foyle said:

I once stumbled upon an engineer's forum where the participants were discussing how to prolong blade life for their razors. One of them had the patience to actually wet and let air dry a blade for about 30 wet and dry cycles (as I recall this took him about 15 days using two cycles each day) without shaving with it and noted that when the blade was finally put to use it shaved like it was brand new. Corrosion played no part at all the blade dulling.

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Just wet/dry cycles on their own would do nothing at all to stainless steel, no matter how many cycles you put it through. However, a microscopic speck of salt or mechanical abrasion of the surface can start a corrosion process specific to stainless steel which will continue until the metal dries out completely. This is because the salt or abrasion destroys the thin layer of oxidised chromium and exposes iron underneath. A combination of chemical and geometric factors means that a tiny pit will form, or a wider area can corrode if you have something to form a crevice, like a layer of dirt.
This means that a new blade would be entirely resistant to corrosion, but once you shave with it then unless you wash and dry it extremely thoroughly, specks of dirt and salt from your skin or the soap will be left behind which will cause corrosion.

With regards to the article, I feel that 40% humidity is not representative of what a real blade would be exposed to. Many peoples bathrooms will approach 100% humidity after the shower is used, and this may happen several times a day in a large household, and as my own house is an old damp-prone building the bathroom can be at around 60-80% humidity through the rest of the day. These conditions could make a huge difference, at 40% humidity a razor may be completely dry after a few minutes to an hour, at 70% the razor may look dry but retain specks of water through the entire day. This means that during the course of a week, in a more humid environment corrosion is occurring for 10-20 times longer.
I have actually left used blades in my bathroom, and after a week found slight rust stains on the surface they were left on.

Cool I would like to see the difference between different blades also.