What makes curly hair curl? : Short Wave Hair scientist Crystal Porter explains the science behind curly hair. (Hint: It involves mushy cells in teeny-tiny tunnels.) Plus, a bit of listener mail from you! Which you can always send by emailing shortwave@npr.org.
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Micro Wave: What Makes Curly Hair Curl?

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Micro Wave: What Makes Curly Hair Curl?

Micro Wave: What Makes Curly Hair Curl?

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  • <iframe src="https://www.npr.org/player/embed/954535546/954632041" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
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You're listening to SHORT WAVE from NPR.

Maddie Sofia here with Ariela Zebede, former intern, now with her first Micro Wave episode.

ARIELA ZEBEDE, BYLINE: Hey, Maddie, very excited. Happy Friday.

SOFIA: Happy Friday, AZ. So a Micro Wave - for all of you who forgot, they are short, fact-filled episodes ending with some lovely listener mail. OK. So what fun do you have for us today, AZ?

ZEBEDE: Well, Maddie, lately I've been thinking about all the things you and I have in common...


ZEBEDE: ...You know, a passion for science and mountains and how we both hate how much everyone at NPR makes puns.

SOFIA: Oh, my God, Ariela, you can't say that out loud. Big Pun is very alive here.

ZEBEDE: (Laughter) There's no room for secrets in this team, Maddie. Come on.

SOFIA: There's some room. There's some room.

ZEBEDE: No. Look. You know what? Something else our listeners might not know about us is that we both have curly hair.

SOFIA: That's true. That's true.

ZEBEDE: And, you know, Maddie, I'm a pretty curious person, but I realized that I'd looked at this stuff on my head for years and never really thought much about it.

SOFIA: Same. Same.

ZEBEDE: I had absolutely no idea what makes hair curl in the first place. So I talked, of course, to a hair scientist, Crystal Porter.

SOFIA: OK, awesome. How does one become a hair scientist?

ZEBEDE: Well, Crystal took an unconventional route. She actually got her Ph.D. in chemistry, where she studied polymers and plastics - nothing to do with hair. It wasn't until after getting her Ph.D. that she started to realize the potential in hair research. She applied her materials science background to understanding hair as a biomaterial.

CRYSTAL PORTER: I was really amazed to find out the breadth of different scientific disciplines that go into hair science. So of course, you have the obvious, like the biology and the chemistry, because everything is made of molecules. But then where I fit in is more about the physics of the material and the properties of it.

ZEBEDE: Hair science is cross-disciplinary, Maddie, and with Crystal's help, we're going to take a look underneath the scalp to figure out what makes curly hair.

SOFIA: I'm Maddie Sofia.

ZEBEDE: And I'm Ariela Zebede.

SOFIA: And this is SHORT WAVE from NPR.


SOFIA: OK, Ariela, today we are talking about curly hair science. Take it away.

ZEBEDE: Yeah. So scientists know quite a bit about straight hair, but there's still a lot we don't understand about curly hair. And that's a knowledge gap that's especially felt by Black communities and something Crystal worked to address in the beauty industry. For a while, she was at the L'Oreal Institute for Ethnic Hair and Skin Research.

PORTER: And so I was able to jump on board and start research on hair that was of African descent. So it was perfect because it's, like, a dream to be a woman of color and someone who has a lot of problems and passion about hair.

ZEBEDE: And, Maddie, this research took her all over the world.

PORTER: We went to South Africa. We were in Nigeria, Jamaica. We went to Brazil.

ZEBEDE: And now she's sharing that knowledge with us.

SOFIA: Whoop (ph), whoop.

ZEBEDE: To start us off, Crystal took me beyond the part of hair that we normally see. There are strands of hair on our heads, right? But hair actually extends deeper than that. It sits in hair follicles, which I think of as teeny-tiny tunnels under the skin. And these follicles come in lots of different shapes.

PORTER: I often envision that you can have, like, a golf club, how you can see that it's kind of flat, and then it curves up until it's straight. You can have that extreme, or it can just be straight up-and-down and anywhere in between.

SOFIA: OK. OK. So these tunnels are getting fancy out there.

ZEBEDE: Yes, they are. And that golf club or curved follicle will tend to give you the tightest curls while that straight up-and-down tube will give you straight hair. Those are the two ends of the spectrum, but there's tons of variation. Remember, there are lots of different types of curly hair, different degrees of curliness and kinks and bends.

SOFIA: Sure. Sure. OK. OK. So the follicle makes a difference, but I feel like curly hair is much more complicated than just the shape of the follicle, right?

ZEBEDE: Yeah, definitely. Let's take it a step deeper and talk about how hair grows.


ZEBEDE: It starts at the bottom of a follicle. The cells down there are multiplying wildly, and these cells start off mushy and gel-like.

SOFIA: Right. But the cells kind of travel up the follicle, and then they harden and die, which makes the hair that we know so well.

ZEBEDE: Yes. And when these cells harden, they shrink. Now, in a straight follicle, both sides of the hair are hardening at about the same time. But in a curved follicle, the cells on one side of the curve harden and contract earlier than the other, which forces the longer portion to bend towards that shorter portion, creating a curl.

SOFIA: So these beautiful locks of ours are due to one side of a piece of hair ending up longer than the other side?

ZEBEDE: Yeah. It's kind of like when you're wrapping presents. Have you ever done that ribbon-curling trick with a pair of scissors?

SOFIA: Yeah, like where you run scissors along the ribbon, and then, all of a sudden, it curls.

ZEBEDE: Yeah. So how that works is basically one side of the ribbon is getting stretched out to be longer than the other side of the ribbon.

SOFIA: Oh, and those different lengths force the ribbon to curl. OK. All right. I've been doing this my whole life, Zebede. I had no idea.

ZEBEDE: Me neither, Maddie. Me neither. And, look, there are other factors beyond just follicle shape and this asymmetry we're talking about that make curly hair. Scientists are still trying to figure out how all of this works.

SOFIA: OK. All right. Got it. You know, Ariela, there's another thing that I'm curious about. What about when you, like, put wet hair in braids, and that kind of, like, changes the texture when you take it out? Like, what, scientifically, is going on there?

ZEBEDE: Oh, you're going to like this one, Maddie. There are a few different types of connections that hold curly hair together. One type is called hydrogen bonding, and when hair gets wet...

SOFIA: Oh, all of a sudden, there's a bunch of new hydrogen in town, you know? That H in the H2O, baby.

ZEBEDE: Exactly. And that water breaks those hydrogen bonds that normally hold your hair together, which makes hair easy to manipulate.

PORTER: For those of you who remember rollers - I don't even know how many people use rollers now, but (laughter) - it's based on the concept of you setting your hair. So when you set your hair, you're disrupting the hydrogen bonds when it's wet, and then you're allowing it to dry.

ZEBEDE: And as the hair dries, the water goes away, and the hydrogen bonds reform based on the position you force them into while the hair was still wet.

SOFIA: But these changes are temporary, right? Like, hair pretty much does whatever it wants again pretty quick.

ZEBEDE: Yes, definitely. And that's because of moisture in the air that's coming in and affecting those hydrogen bonds again. But this time, you don't have your curlers in, so it just takes on its normal shape again.

SOFIA: All right, AZ. I learned so much today about hair and, weirdly, about wrapping presents.

ZEBEDE: (Laughter).

SOFIA: Thank you for bringing this on the show.

ZEBEDE: You got it, Maddie.

SOFIA: OK. Before we go, in traditional Micro Wave fashion, let's end on some listener mail.

ZEBEDE: Yes. I have a great one from Carmen (ph), but, honestly, Maddie, you're not going to like it because it's about an error you made in one of our old episodes.

SOFIA: What are you talking about?

ZEBEDE: You remember that episode about the connection between smell and memory? We recently encored it again over Thanksgiving, so we've actually published this horrible mistake twice.

SOFIA: Ariela, you're making me sweaty. Please continue quickly.

ZEBEDE: OK. Here's what Carmen wrote.

(Reading) Dear SHORT WAVE, I'm a huge fan of your show. I started listening this summer during marathon training...

SOFIA: OK. Real low-key. Sure.

ZEBEDE: (Reading) ...And I'm almost through every episode. My friends probably hate me for the number of science facts I tell them that, quote, "I heard on a podcast."

SOFIA: Are they really your friends?

ZEBEDE: (Reading) That said, I have a bone to pick. The first time I heard the episode The Special Connection Between Smell And Memory, I decided to let it slide. But when I heard it replayed, I simply had to bring it up.

SOFIA: Oh, my God. What is it?

ZEBEDE: (Reading) The ET ride ET Adventure is located at Universal Studios, Fla., not at Disney World, as mentioned in the episode. I mention this because I love both Universal and Disney, and I want to help appease all the other fans who noticed this critical mistake.


ZEBEDE: (Reading) L-O-L. That is all.


ZEBEDE: (Reading) Thank you for everything you do, and Happy New Year.

SOFIA: Wow. I feel like I went to Disney World, and that's where I rode it.

ZEBEDE: No, Maddie. Carmen and the other die-hards are right. I checked.

SOFIA: This is my nightmare, Ariela. You are bringing me on-air and bringing me a correction. Why would you embarrass me?

ZEBEDE: Maddie, as a fact-checker, I just - we owe our listeners the truth, you know? That's our mission here.

SOFIA: Wow. You know what? You're right. I apologize to our listeners, to Steven Spielberg, tiny Drew Barrymore, my family specifically.

ZEBEDE: (Laughter) She'll be OK, we promise, everyone. Maddie?

SOFIA: All right. Ariela Zebede, former intern, current superstar, thank you so much for your first-ever reported episode for SHORT WAVE.

ZEBEDE: Thanks for having me, Maddie.

SOFIA: Honestly, we're really proud of you. I'll say it.

ZEBEDE: You're so embarrassing, truly, for yourself and for me.


SOFIA: This episode was produced by Brit Hanson...

ZEBEDE: ...Fact-checked by Berly McCoy and edited by Viet Le. Special thanks to Gill Westgate (ph).

SOFIA: I'm Maddie Sofia.

ZEBEDE: And I'm Ariela Zebede.

SOFIA: Thanks for listening to SHORT WAVE from NPR.


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