Curly hair: macroscopic features

First off, let me state that this thread is not about the differences between curly and straight hair. Discussions of inter-keratin triple helix disulfide bond linkages will not be permitted in this thread. Nor will any mention of hair straighteneing or curling protocols/chemistries. Friends, cast these off as they are irrelevant.

What we’re interested in here is the the macro-structure of curly hair. Specifically, why do curls form?

For the purposes of this discussion, let’s define a macro-curl as a structure consisting of hundreds of individual hair strands originating from a small patch of scalp. Micro-curl, OTOH, is the kinking and twisting of an individual hair strand caused by the aforementioned (and now unmentionable) inter-strand disulfide linkages. My question is, what forces hold the individual strands together in this quasi-stable (and durned cute) configuration. This seems to occur best in hair that is only moderately curly on a micro level.

Too much micro-curl, and forces which separate the strands of hair dominate, resulting in serious fro-age. Not enough, and strands hang separately, lifeless and limp.

Interestingly, the addition of a compound which bonds hair strands to one another (gel, pomade) counteracts the fro or frizz effect, allowing macro-curls to form in otherwise unruly hair. This underscores the necessity of an inter-strand bonding force in the formation of macro-curls.

It occurs to me that temporary inter-strand bonding as a result of wetting the hair might provide a template for macro-curl formation. Once hair is dry, though, the macro-curls remain.

How do macro-curls get organized? What promotes their stability?

I ask Google, “Why macrocurls form”.
Google replies, “Did you mean: why macrocells form?”

Good luck with your quest! :smiley:

Egads!! DDG came up empty with her research-a-ma-phone. Surely, this does not bode well for science.


Completely making this up as I go along:

Each follicle is created the same way, by the same DNA doodads, so isn’t it reasonable that any two adjacent follicles are similar to each other? That doesn’t explain why all the hairs on the head don’t look alike, though.

If hairs are like their neighbors, then you have to deal with the follicle orientation. I would think that whatever process is responsible for making arm hair go in a specific direction in a specific area would also make the head hairs all point in an organized way too.

I have curly hair that is macroscopic on two levels: the curls are large, and thus completely absent until the hair is at least a couple inches long, and it creates the macroscopic curls that the OP is about. The only other area of body hair that has hair long enough and dense enough to exhibit macroscopic curl features does exhibit such curls.

Perhaps examining the problem from an evolutionary standpoint would be more useful. In eras before modern hair care, would macro curly hair be a more desirable trait than curly hair that doesn’t have the macro structure in populations where both traits were present and all else was equal?

One could even argue that it must still be a more desirable trait for some people, or we would have no concept of a ‘perm’ or hair curlers or any of that cruft.

Don’t ever again post such a question when I’m about to go to bed. :mad: I hate you. :slight_smile:

The good thing: It was easier than I thought and I could fall asleep at 23:44, tightly hugging a notebook full of squiggly lines.

The bad thing: Can’t explain it without diagrams.

Imagine a cylinder with a line wrapped around (1). This is our model of a curly hair. Unroll this spiral, and it will be the diagonal of a rectangle in a flat coordinate system (2). Note that the relative position of two spirals is only determined by their distance, rotating or three-dimensionally shifting one of them would both map onto shifting its origin sideways in this system (3).

If one of these hairs gets pushed, it will pivot around the point of its origin (4). I think I omitted some shearing of the rectangle (no hair cutting jokes, please :)) (I now realize the aspect ratio of the browser font took care of it!), and it would rather bend than pivot, but that doesn’t affect the following theory.

Now even on the head of Homer Simpson is more than one hair. When two hairs meet, there will be a point of contact, at which forces are exchanged. One hair gets pushed left “*”, the other right “#” (6), resulting in the contact point moving further down on the length of both hairs.

This tends to equalize the angles of them. Of course if the force gets too strong, the contact point will move over the end of one hair (7), leaving the hairs free to get entangled in another place, thus statistically lumping them together in macro-curls with minimal elastic stress.

Note that what looks like the hairs could simply pass by each other results from our coordinate transformation. In reality it would be like trying to separate two entangled spiral springs.

The cohesion of hair gel adds another force, holding the hairs together, resulting in an enlargement of the spatial cells of acceptable force.

 (1)                                       ^     ..
 ____   ^                                  :   .'*`  (4)
(____)  |           <-|-> (3)              : .'  * '
|   *|  |--------+    |                    +'   *  `
| ** |  |       *|    +--------+---+  ^  .':   *    '
|*   |  |     ** |    |   |   *|  #|  `.'  :   *    `
| .. |  |   **   |    |   | ** |## |   `   :  *      '.>
|   *|  | **     |    |   **  ##   |    '  : *      .'
| ** |  |*       |    | **| ## |   |    `  : *    .'
|*   |  +--------+->  |*  |#   |   |     ' :*   .'
| .. |                +---+--------+     ` *  .'  \
|   *|     (2)                            '*.'angle\
| ** |                                    `'--------->
|*   |
`----'          #     *
               #    **
              #   **                       # **
             #  **            (6)        ##**
   (5)      # **                       *O*
           #**                       *##
^    ^   *O*             ^    ^   ***#  ^
|    | **#               |    | ** ##   `-point moves
|    ** # ^              |   ***  #        up and right
|  **| #  |              |  * | ##
|**  |#   point of       |**  |#        * turns < this way
+--> +-->   contact      +--> +-->      # turns > that way

  (7)   *
     * #
 ^  * #
 | *  #
 |*  #

Now to the question even Cecil can’t answer: Why, oh why, did I do this :confused:

Did you know my first post ever was about rotating growing hair and drawing spirals on it?


That sounds like the answer.
[sub]sigh, I have no idea what you’re talking about. Note to self: don’t ask a question whose answer is beyond your comprehension.[/sub]

So now I know there are curly hair experts out there…

Why was I born with very straight blonde hair only to have it turn into a large mass of extremely curly brown hair around the age of 6 or 7?

Is it DNA, hormones, environment, or what? Did I just grow more hair that started pushing itself every which way?










Well, OK, maybe a short aside. From

Come on now, you added that “transformations between” thing after i posted :slight_smile:

I don’t want to know the difference. I know the difference. It’s my hair! I want to know why something like that would happen.

BUT, I will refrain from asking in this thread and ask again sometime, when you least expect it, and you will forget how much I have offended you ;):stuck_out_tongue: