Why do dull razors cut you more when you’re shaving?

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Why do dull razors cut you more when you’re shaving?

In: Engineering

When something is sharper it cuts smoother and easier. Imagine trying to cut something and the blade is dull, it won’t cut very well or hardly at all. Same principle applies to a razor blade. It cuts hair easier when the blade is sharp, but won’t hardly cut when it’s dull. A dull razor pulls and tugs on the facial hair which causes it to cut the skin instead of the hair.

Dull blades have burs, little bits of metal twisted into itsy bitsy jagged little spikes like barbed wire pointing in the wrong directions. These burs develop after extended use, or from getting rusty if you wet shave and they oxidize. The little burs are what cuts and irritates your skin when the blade is dull.

Properly sharpened blades don’t have many burs, they are only sharp in the direction they are supposed to be. They cut the hairs that stick up in front of them, but not the skin which is parallel to them.

A dull razor will catch on hairs and pull on them, pulling the skin into a fold which can then get cut.