eli5 How does razor blade dull on hairs when razor blades are made of steel and they are much higher on mohs scale?
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knifemaker here:
Cutting edges can actually dull in several ways. The first and most obvious is simply abrasion. Even though steel is harder than hair, it may be rubbing against hard particles that are on skin or hair. This wears down the edge and makes it more blunt.
Similarly, microchipping could cause small pieces of steel to break off on a very small scale, causing it to dull if it has been heat treated improperly and is too brittle.
Another cause for dullness is edge rolling, which happens in softer steels, where rather than chipping when hitting something hard, the edge will deform. In this case it’s dull because the sharp part no longer makes contact with the hair.
Corrosion can also cause dulling on razor blades because they are so incredibly thin. It’s probably best to store them in a dry place until they’re ready to be used
Here’s a writeup by a PhD metallurgist: https://knifesteelnerds.com/2021/01/11/what-causes-razor-blades-to-dull/
The nasty industry secret is that the blades don’t really go blunt/dull, as much as they get gummed up with residue from you and shaving agents.
You can run a month on a blade if you clean them after use. (isopropyl alcohol or similar solvent) even a thorough reverse-whipedown under scolding water helps a lot
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