The Scientific Reason Why Razors Don’t Stay Sharp for Long

[Flyboybob]

Here’s an article that explores why razors don’t stay sharp. I wonder if this also applies to electric shavers?

The Scientific Reason Why Razors Don't Stay Sharp for Long

When soft hair hits the blade’s weak points, it causes the metal to chip apart

www.smithsonianmag.com

 

[Scaramouche]

An ongoing discussion in another part of the forum:

Cutting-Edge Research Shows How Hair Dulls Razor Blades

Cutting-Edge Research Shows How Hair Dulls Razor Blades

www.badgerandblade.com

It is interesting that many report a better shave after the first use of a DE blade, and at least one semi-scientific study reports increased sharpness after first use for most blades, measured by pressure required to sever a stretched fiber (presumably by burnishing or removing the factory coating);

Razor Blade Sharpness Testing

Razor Blade Sharpness Testing If you are only interested in the Razor Blade Sharpness Summary and already know how the testing works, click here to see summary tables. I have a background in Materi…

www.refinedshave.com

Electric blades are somewhat self-sharpening, burnishing the edges on the inner foil or comb surface. There's a limit to how sharp an older blade can be, however, because of the increase in relative thickness the further away from the edge and toward the center mass of the blade you get. The hardness also decreases farther from the edge, as the hardened martensite wears away exposing the softer phases of a steel blade. A DE blade sacrifices toughness for hardness, and the property of having an edge that can be made very sharp, but brittle (hence the chipping). The useful life of a DE blade is therefore measured in ones - one shave, two shaves, three shaves. A dozen good shaves with a DE blade is not unheard-of, but remarkable.

An electric blade, conversely, can cycle across a foil 233 times in a second in the case of Panasonic shavers, so a too-brittle edge would be quickly worn away. Hence the steel in electric blades sacrifices hardness (somewhat) for toughness, and may only show a decrease in sharpness after months, not days, of use. They get away with it (providing a close shave) by virtue of the speed they're moving - similar to a lawnmower versus a sickle. A lawnmower blade can be considerably less sharp than a sickle blade and still cut grass - not so much the reverse. But the same thing that wears a DE blade wears an electric - passing through multiple hair shafts multiple times - and eventually dulls for the same reasons.

 

[Clay S]

An ongoing discussion in another part of the forum:

Cutting-Edge Research Shows How Hair Dulls Razor Blades

Cutting-Edge Research Shows How Hair Dulls Razor Blades

www.badgerandblade.com

It is interesting that many report a better shave after the first use of a DE blade, and at least one semi-scientific study reports increased sharpness after first use for most blades, measured by pressure required to sever a stretched fiber (presumably by burnishing or removing the factory coating);

Razor Blade Sharpness Testing

Razor Blade Sharpness Testing If you are only interested in the Razor Blade Sharpness Summary and already know how the testing works, click here to see summary tables. I have a background in Materi…

www.refinedshave.com

Electric blades are somewhat self-sharpening, burnishing the edges on the inner foil or comb surface. There's a limit to how sharp an older blade can be, however, because of the increase in relative thickness the further away from the edge and toward the center mass of the blade you get. The hardness also decreases farther from the edge, as the hardened martensite wears away exposing the softer phases of a steel blade. A DE blade sacrifices toughness for hardness, and the property of having an edge that can be made very sharp, but brittle (hence the chipping). The useful life of a DE blade is therefore measured in ones - one shave, two shaves, three shaves. A dozen good shaves with a DE blade is not unheard-of, but remarkable.

An electric blade, conversely, can cycle across a foil 233 times in a second in the case of Panasonic shavers, so a too-brittle edge would be quickly worn away. Hence the steel in electric blades sacrifices hardness (somewhat) for toughness, and may only show a decrease in sharpness after months, not days, of use. They get away with it (providing a close shave) by virtue of the speed they're moving - similar to a lawnmower versus a sickle. A lawnmower blade can be considerably less sharp than a sickle blade and still cut grass - not so much the reverse. But the same thing that wears a DE blade wears an electric - passing through multiple hair shafts multiple times - and eventually dulls for the same reasons.

Another consideration with electrics would be that since they use more of a scissoring action to cut hairs, the hairs moves less, making it less likely to micro-chip the edge. It would be hard to get an image of it in action though.

 

[Flyboybob]

Another consideration with electrics would be that since they use more of a scissoring action to cut hairs, the hairs moves less, making it less likely to micro-chip the edge. It would be hard to get an image of it in action though.

I think your comment that electric shavers use more of a scissor action is spot on. That’s why the cutters stay sharp for so long. How often do you have your scissors sharpened?