Why do razors have multiple blades?

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Often shaving commercials brag about how their razor has more blades than their competitors, are more blades somehow better, and if so why?

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Oh a nice easy one! There’s a really satisfying animation I saw about this years ago that has become ingrained in my memory, but I couldn’t find it so [here’s one](https://www.youtube.com/watch?v=20SSZH2JI2s&ab_channel=Gillette) that’s effectively the same.

Basically, when a blade passes across a hair, it doesn’t just cut it, it also pulls it out of your skin slightly. If you then follow it up with another blade before it can sink back in, the next blade can cut the extra bit that got pulled out, that the first blade didn’t get. Then, it pulls it out even more, allowing a third blade to cut even further down.

The reason cutting further down is better is because the remaining hair will stick out of your skin a shorter distance, resulting in a smoother feel and less irritation.

Two blades make it a little easier to get a close shave with one pass. Razors with more than two blades come from Marketing, not Engineering.

If you are shaving using a straight razor, only one blade is necessary. However, very few people shave with straight razors because it is dangerous and time consuming in its own way. Instead, nearly all razors are safety razors. Safety razors have guards around the blade to ensure it can’t cut too deeply into the skin. Hair can build up between the blade and that guard, making the blade less effective and more likely to snag on the skin. You can (usually) dislodge this hair just by rinsing the razor head, but the more blades there are on the razor, the harder it is to clog all of them, and the less frequently you have to rinse.

Answer: some of the ads for those blades will show you why. It’s akin to having a dual-deck riding mower–you get multiple attempts to cut each blade of grass you go over.

The first blade “cuts” (really, drags/lifts the hair out of the pore and rips it with the leading edge of that blade), then the second blade comes along immediately, before the remaining hair retracts, and again “cuts” (separates) another segment of the hair, and so on.

There’s a limit to how efficient multi-blade razors can be (six blades doesn’t get you much more than three or four), but it gives you a little “cleaner” shave (the hair remnants are now at pore level or slightly below–which has its own host of issues), which makes your face/legs/whatever smooth to the touch.