Shaving: shear of bristles (e.g., lawnmowers) and cold steel mechanics

1.a. I am assuming for the sake of argument that the hairs of one’s beard softens when it’s wet. You can’t mow the lawn when it’s wet, so how come it’s easier to shave the beard when it’s wet? Shouldn’t the bristles be as stiff as possible to be sheared, and not pulled?

1.b Or is it that, if the bristles don't soften, the cream or soap softening the lower flesh where the bristles surface makes them somewhat "pullable-outable" to make up for not being easily shearable? (I am not talking about the emollient's effect of preventing abrasion on the skin surface.)

Are 1.a and 1.b reconcilable? Eve before that, correct me on which parameters are wacky.
2a. In the movie Miller’s Crossing one of the bad guys, just before he gets whacked, explains to his driver that the key to getting a good shave is lathering up your face and then running your blade under cold water. The cold water, he says, tightens up the steel.

That seems to make sense as basic mechanics. Empirically it never has worked for me–shattering my faith in Hollywood–perhaps because it washes out the emollient’s effect on the bristles mentioned above (which is left to be demonstrated).

2.b. I think about these things often while I’m shaving.
2.b.1 I cut myself a lot.

There is an experiment going begging here:

Try to shave your wet & lathered beard with a lawnmower and see how often you cut yourself.

Your Dawin Award nomination depends on it.

Premise #1 is false.
Putting hair in a room/shower temperature water for a few seconds before shaving will not soften the bristles through hydration. Placing them in a high pressure steam bath for a couple of hours will, though again, this is not a recommended shaving technique.

You’re talking about very different things.

Just from my own experience mowing lawns, the main reason that you can’t mow a wet lawn isn’t really because the mower won’t cut the grass. It’s mainly because, when its wet, the cut grass all clumps together and clogs up the mower blades. I’ve mowed wet grass, and if you’re willing to stop the mower every few minutes and unclog the blades, it generally works pretty well.

Grass is already wet when it’s alive. It’s full of water, unless you’re mowing a brown dead lawn which is analogous to what your facial hairs would be like. Another thing to consider is, you don’t care how the dirt feels when you mow the lawn, whereas you do care how your face feels when you shave.

It doesn’t take a few hours of high pressure steam to soften bristles. A few minutes with a hot towel wrapped on your face is best, or the shower is almost as good.

Running the blade under cold water doesn’t tighten the steel appreciably unless you’re plunging it into liquid nitrogen.

Using your hands to lather isn’t as good as using a good shaving brush. It helps get the bristles pointing up (like in that amusing 'Lectric Shave commercial). The lather is also supposed to help with the blade sliding across your skin so it doesn’t bind to it causing razor burn and poor razing.

My 35 years of shaving experience disagrees with this. I know the conventional wisdom has always been hot towels, etc., but the conventional wisdom is often wrong.

The hair on your face is not dramatically different than the hair on your head. Coarser, maybe, but it’s still made of the same stuff with the same structure. You don’t have to stand under a hot shower for hours for your hair to become totally limp when it gets wet–more like a few seconds. Why would your beard be any different? Washing your face with soap to get rid of oils that would repel water is really all that’s needed to thoroughly wet and soften the beard. The whole hot towel thing is really just because it feels good.

If you’re arguing that the water doesn’t do anything at all, try shaving without it and let me know how that works for you. :slight_smile:

I do agree with the part about how high-pressure steam is not recommended shaving technique. :smiley:

It’s worth noting that electric razors - which shear, rather than cut, hair - do in fact work best on dry facial hair.

The biggest reason you shouldn’t mow a lawn wet is that the clippings will clump and clog the mower and fall into the lawn in big clods that not only look ugly but also may kill the patches of grass they sit on.

It isn’t that difficult to shear hair. Also, I bet the cutting edge of a razor can’t really maintain a different temperature than the skin and hair and lather for long enough to matter - razors are thin, the blade edge is thinner, and anyway they are generally stainless steel which has pretty poor thermal conductivity as metal goes. How much of the hair is actually outside of the skin, and how the skin feels and behaves under any kind of blade, and how it feels to the hand afterwards, are all much more subtle issues. There may be enough perception difference to completely overwhelm any differences in the cutting per se.

Shaving cream works because it lubricates the face, not because it hydrates the whiskers. That’s why you can shave with any lubricant, including motor oil or peanut butter (though they are harder to wash off, making them less than optimal) if no water is available. The shaving cream of lotion allows the blade to move without catching the skin.

The hair on your head is not really hydrated either. There is just a lot of water trapped between the individual strands of hair. A nylon paintbrush bristle won’t absorb any paint, but the brush still works via the same principle.

I think hair probably does get hydrated a little. It has a fairly high surface energy and is not fully halogenated, being protien. It probably has a takeup on the order of a couple percent, no? Even nylon will take up an easily measureable quantity of water internally.

Note that you can build a humidity meter using a strand of human or other animal hair wrapped around a little axle to turn an indicating pointer. I built two of these with hairs about 20" long - one from my grandmother, which was noticeably darker at one end and grayer at the other, and another from a hair collected from a barbed wire fence with horses hanging around it. The hair gets a little longer when the humidity is higher.

I doubt that it makes the hair different enough to matter when shaving, but hair must be able to absorb water.

Yeah well, having studied textile technology I could bore you shitless over the differences in hair and wool fibre character resulting from composition of the para, ortho and mesocortex fractions of hair and wool fibres.

RealityChuck and ivn1188 are on the money: water, oil, lather etc is about hydrating/lubricating the skin. Shaving is applied dermatology, not fibre technology.

Hair/wool being based on an alpha helix structure can, under the right conditions stretch almost without limit. Which is why you don’t wash woollen garments in hot water. At university one of the Profs had a experiment with a single wool fibre that have been under small load for 25 years in a humidity vessel and was still elongating.