Chris Hsu for American Public Media
Our knives are drawn and ready to mince and dice our way through the science of chopping. In this episode we'll find out what happens to that carrot you're chopping on a molecular level (spoiler alert: the knife never actually touches it!). We also visit knifemaker Moriah Cowles' studio and talk to Splendid Table host Francis Lam to get his chopping tips.
This is the third in a five-part series on the science of cooking, made in collaboration with America's Test Kitchen Kids.
Moriah Cowles heats a piece of steel in the forge at her studio Orchard Steel in Vermont.
Erica Heilman for American Public Media
Moriah Cowles shapes a hot piece of steel into a knife at her studio Orchard Steel in Vermont.
Erica Heilman for American Public Media
Summer Tomato and Peach Salad
Courtesy of America's Test Kitchen
SUMMER TOMATO AND PEACH SALAD
This recipe comes from America's Test Kitchen's upcoming The Complete Cookbook for Young Chefs.
Serves 4 to 6
Prep Time: 10 minutes
Cook Time: 25 minutes
Prepare Ingredients
3 ripe tomatoes
Salt and pepper
2 small ripe peaches
3 tablespoons extra-virgin olive oil
1 tablespoon minced shallot
1 tablespoon lemon juice, squeezed from 1 lemon
¼ cup fresh mint leaves
Gather Cooking Equipment
Cutting board
Small serrated knife
Colander
Medium bowl
Whisk
Rubber spatula
Start Cooking!
1. Use small serrated knife to cut each prep tomato in half (through stem end), then remove and discard core. Cut tomatoes into ½-inch-thick wedges. Cut each wedge in half.
2. In colander, combine tomatoes and ½ teaspoon salt and gently toss to combine. Place colander in sink and let tomatoes drain for 15 minutes.
3. While tomatoes drain, cut each peach away from pit, then discard pit. Slice peaches into ½-inch-thick wedges. Cut each wedge in half.
4. In medium bowl, whisk together oil, shallot, lemon juice, ¼ teaspoon salt, and 1/8 teaspoon pepper. Add drained tomatoes and peaches to bowl with dressing and use rubber spatula to gently stir to combine.
5. With your fingers, tear mint leaves into pieces. Sprinkle mint over salad. Serve
Pitting Peaches
Once peaches are pitted, slice them into wedges and then cut the wedges in half following the same method shown for the tomatoes.
1. Cut small slice off bottom of peach to create flat surface.
2. Slice around pit to remove 4 large pieces. Discard pit.
Tomato Prep
1. Use small serrated knife to cut tomato in half from top to bottom (through stem).
2. Place each half flat side down. Use tip of knife to cut out core from each half.
3. Cut tomatoes into wedges that are roughly ½ inch thick.
4. Cut each wedge in half (cut the short way).
Audio Transcript
Download transcript (PDF)
NANTINE: You're listening to "Brains On," where we're serious about being curious.
GIRL: "Brains On" is supported in part by a grant from the National Science Foundation.
[ELEVATOR DING AND ELEVATOR OPENING]
ELEVATOR: This is Brains On headquarters. Where can I take you?
NANTINE: Hey, Elevator.
MOLLY BLOOM: Elevator, take us to the Brains On lab or kitchen.
NANTINE: Lab or kitchen?
MOLLY BLOOM: I'm so excited for you to see this. It's part lab, part kitchen. It's where we make food, but you know us. We always have some new idea we're trying to work out.
ELEVATOR: Here we are, Brains On lab or kitchen. Goggles on. Taste buds ready.
MOLLY BLOOM: Thanks, Elevator.
SANDEN TOTTEN: Hey, Nantine. Hey, Molly. You guys, come over here. You got to see this.
MOLLY BLOOM: What have you got there, Sanded?
SANDEN TOTTEN: I have been tinkering for months, and I finally got it working. Here it is. Dun, dun, dun, ah, the Lukewarmanator.
[BELLS CHIMING]
NANTINE: It's so sparkly?
SANDEN TOTTEN: Huh? Oh, uh, yeah, I dropped a bunch of parts in that vat of glitter downstairs by accident. But, look. You take this super hot soup that's been bubbling away on the stove for an hour.
NANTINE: [SNIFFS] It smells so good.
SANDEN TOTTEN: Yeah, but way too hot to eat, so I put it in the Lukewarminator, press this button, and--
[RINGING]
[DING AND DOOR OPENING]
Go ahead, try it now. Try it, try it.
MOLLY BLOOM: [SIPS] Oh, my gosh, it's not hot at all anymore.
[SIPS]
And it's not too cold either.
SANDEN TOTTEN: Exactly. It's perfectly lukewarm, the best temperature in the world. I can put in ice water or frozen peas, and voila, lukewarm water, lukewarm peas. Genius, right?
MOLLY BLOOM: You will never burn your tongue again.
[CLATTERING]
MARC: Ah, look out!
NANTINE: What's going on back there?
SANDEN TOTTEN: Oh, uh, that's Marc. He's working on his traveling kitchen idea?
MOLLY BLOOM: It looks like he's just wearing a jumpsuit with a blender taped on one arm and a toaster taped to his back.
SANDEN TOTTEN: Yeah, it's a work-in-progress.
MARC: Hey, Sanden, can I get your help? The toast is ready, but I can't reach it!
SANDEN TOTTEN: Coming, Marc. Uh, I'll see you guys later. I'm going to go help with that.
NANTINE: We'd better head to the studio anyway.
[ELEVATOR DING]
ELEVATOR: I can take you there, but don't you want to try anti-gravity mode first or visit a spork factory?
MOLLY BLOOM: Thanks, Elevator, but we're good.
ELEVATOR: Fine, studio it is.
[MUSIC PLAYING]
(SINGING) Chill, chop, mix, heat. Reverse the order, then repeat. Eat, mix, chop, chill the recipe for every meal.
[SNAPPING]
[CRUNCHING]
[SODA POURING]
Chill, chop, mix, heat. Reverse the order, then repeat. Heat, mix, chop, chill the recipe for every meal.
[ICE IN GLASS]
MOLLY BLOOM: You're listening to "Brains On" from American Public Media. I'm Molly Bloom, and my co-host for our series on the Science of Cooking is Nantine Bah from New York City. Hi, Nantine.
NANTINE: Hi.
MOLLY BLOOM: So, Nantine, you are part of a program called Harlem Grown, where you learn about growing and cooking your own food. Can you tell us a little bit about the Harlem Grown garden? What kind of vegetables and fruits do you grow in the garden?
NANTINE: We grow a lot of herbs. Like, we grow parsley, sage, basil, dill. We also grow cucumbers and tomatoes, swiss chard. Collard greens, we grow those too.
MOLLY BLOOM: So when did you start using a knife for cooking?
NANTINE: Second grade because my after school had like a cooking activity. Like, there'd be a cooking teacher, and she would teach us how to make basic things like yogurt parfaits and stuff. And they also took us to Columbia University for some cooking classes.
MOLLY BLOOM: Cool. When you first started using a knife, were you nervous about it or were you like, let's do this?
NANTINE: I wasn't really nervous because it was a plastic knife, so it was like-- I was like, I can't cut myself with this.
MOLLY BLOOM: So what tips do you have for kids who might not have started using knives yet and might feel a little nervous about it?
NANTINE: Don't use a knife that looks dangerous because you're going to get scared, you're going to start overthinking it, and you might end up cutting yourself in the process.
MOLLY BLOOM: So start with like a smaller, more manageable knife for your smaller hands?
NANTINE: Yeah.
MOLLY BLOOM: Good tip.
[MUSIC PLAYING]
We are very lucky, because Nantine is not the only culinary expert helping us out with this series. We've partnered with the brilliant minds at America's Test Kitchen to answer your many food-related queries.
NANTINE: So far, we've tackled your questions on chilling and heating the stuff we eat.
MOLLY BLOOM: This week, our knives are drawn and we're ready to chop.
NANTINE: We're starting with this question.
BEN: Hi, my name is Ben. And I live in Ventura, California. My question is, why do things that are thinner cut better than things that are lighter?
MOLLY BLOOM: Yeah, why is it you can slice so nice with a thin blade but if you use something wider, like a rolling pin, you just smush it? Brains On producer Sanden Totten is here with an answer.
[DOOR OPENS]
SANDEN TOTTEN: Hey, guys. I just made the most amazing lukewarm latte. [SIPS] Ah. All right, I'm ready to answer this question. But first, we need to understand a little bit more about how knives slice. Let's start with this knife and this carrot.
[CHOPPING SOUNDS]
Chopping it seems like no big drama, right?
NANTINE: I would say there is zero drama happening right now.
SANDEN TOTTEN: Yeah, I used to think that too, then I called up Julia Majors with the American Institute of Physics, and she set me straight.
JULIA MAJORS: Well, it's fascinating at all levels. When you're actually just making a basic cut, you are using forces of materials that are pushing against each other. And at that point of contact, then you have kind of a battle of one material over the other.
[DRUM BEATING]
MOLLY BLOOM: All right, soldiers, that knife is trying to tear our carrot army apart. Will we let it?
GROUP: No!
MOLLY BLOOM: That knife thinks we're weak. Are we weak?
GROUP: No!
MOLLY BLOOM: That knife wants to chop us up and put us in a salad. Are we a salad?
[AGREEING]
MAN: I think we'd be good.
WOMAN: Yeah, totally.
MAN: Yeah, let's do it.
SANDEN TOTTEN: Let's look a little closer at what's going on. Uh, where's Marc's zoom ray? Let me see.
[CLATTERING]
NANTINE: Zoom ray?
MOLLY BLOOM: It's something Marc put together a while back, but don't worry, it works way better than the traveling kitchen.
NANTINE: Phew.
SANDEN TOTTEN: Yes, I found it. So let's zoom in on this carrot knife battle.
VOICE: Zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom.
SANDEN TOTTEN: Both carrots and knives are made up of these things called molecules.
MOLLY BLOOM: Yes, everything is made up of molecules, they're the building blocks of the universe.
SANDEN TOTTEN: Totally, totally. Now, if we zoom in on a specific molecule--
VOICES: Zoom.
[MUSIC PLAYING]
SANDEN TOTTEN: --we see it's made up of even smaller parts called atoms.
NANTINE: Whoa. Those atoms have a center and then some kind of weird cloud around them. What is that?
SANDEN TOTTEN: Those are clouds of electrons. Electrons are these itsy, bitsy, tiny, winey buzzing little particles that help make up atoms. They're negatively charged and super fascinating. Julia Majors told me that it's here at the level of the electron cloud that the cutting actually happens.
JULIA MAJORS: You're going to have that cloud of electronic charge right at the edge of that carrot material. And then, you're going to have another cloud of the electron charge around the metal. And when they approach each other, then you're going to have, at the end of the day, its electromagnetic forces on that microscopic level.
SANDEN TOTTEN: Both the carrot's electron clouds and the knife's electron clouds are negatively charged. And remember, opposites attract, but samesies push awaysees, so that means these two negatively charged clouds are going to push each other away, kind of like how two similar sides of a magnet push each other away.
[MECHANICAL ECHO]
MAN: Come on, Team Knife, let's shove these carrot clouds out of the way.
MOLLY BLOOM: [GRUNTS] Stand your ground, carrots. Hold tight. Push right back.
SANDEN TOTTEN: Now, to answer Benjamin's question, here is why a sharp, narrow blade is better than a wide, flat one. See, when you're pushing down on the knife, you are applying pressure. The narrower and sharper the edge of the knife, the smaller an area the force of the knife goes to, leading to more pressure for the same effort.
If you have a wide, flat edge, the force is spread out over a large area, so the pressure is weaker overall. You don't want that because you're going to need all the force you can get to break apart that carrot. And since the forces that hold the metal molecules of the knife together are stronger than the forces holding the carrot molecules together, that carrot has a really tough time with a sharp knife.
MOLLY BLOOM: Come on, Team Carrot, keep it together!
MAN: Push harder, knife atoms. [HEAVY EXHALE] We're almost there.
JULIA MAJORS: At some point, that material is going to break apart, so that part of the carrot goes on one side and part of the carrot goes on the other side of where they meet.
MOLLY BLOOM: I slipped. I lost our grip. Oh, no!
[RUMBLING]
MAN: Yes, knives did it! Coming through. Ha, ha! Move out of the way, carrot heads. [CHUCKLES]
SANDEN TOTTEN: So when you cut something, you're not splitting carrot atoms, per se, but you are pushing them away from other carrot atoms that make up carrot molecules and carrot cells with the knife. And it gets even weirder. These carrot and knife atoms push each other away with electromagnetic force, which means they never actually touch each other at all.
MOLLY BLOOM: What?
SANDEN TOTTEN: I know, right? So the knife moves forward, and the carrot molecules part around it, leaving the path wide open for the blade.
MOLLY BLOOM: OK, you are blowing my mind right now. So when I cut something with a knife, the knife and the thing never actually touch?
SANDEN TOTTEN: Nope.
JULIA MAJORS: And that's true of anything that you touch. Even though you feel it and you feel that touch, when you look really, really at the very interface of your hand and the surface, it's actually not fully, fully touching because of those opposing charges.
NANTINE: So I'm not actually touching this table right now?
SANDEN TOTTEN: Nope. You're just feeling electrons repelling other electrons.
MOLLY BLOOM: So when I sit in this chair?
SANDEN TOTTEN: Just clouds of butt molecules hovering over chair molecules, Molly.
NANTINE: This is too much.
SANDEN TOTTEN: Yeah, science can totally mess up your mind, but it will give you something really cool to think about next time you chop a carrot.
MOLLY BLOOM: Thanks, Sanden.
NANTINE: Yeah, thanks.
SANDEN TOTTEN: No problem. Now, if you'll excuse me, this latte got a little too cold while we were talking, so I'm going to go re-lukewarminate it. See you guys.
[MUSIC PLAYING]
MOLLY BLOOM: It's always important to be careful when using a knife. They can do serious damage, even with the mind-blowing physics we just talked about. But here's a safety tip that might be surprising.
SASHA MARX: A sharp knife is actually way, way safer than a dull one.
MOLLY BLOOM: That's Sasha Marx, an editor with America's Test Kitchen Kids.
NANTINE: Dull knives may be more dangerous because you have to push down harder to use them.
MOLLY BLOOM: And that could lead to your knife slipping and cutting you instead of the food. Nantine, what is your favorite knife to use?
NANTINE: A small knife.
MOLLY BLOOM: How do you use it? Do you chop quickly? Do you chop carefully? What is your style?
NANTINE: I chop carefully.
MOLLY BLOOM: Excellent. Always good to be careful. My favorite knife is a serrated knife, those ones that look like little saws that are good for cutting tomatoes or crusty breads. And our friends at America's Test Kitchen Kids shared a great recipe with us for you to practice your knife skills. It's a peach tomato salad, perfect for summer. Here's Molly Birnbaum from America's Test Kitchen Kids.
MOLLY BIRNBAUM: We are chopping and we're using two different types of knives which really gets at how knives behave and which is best for which different type of ingredient, as well as using our hands to tear apart some other types of ingredients.
[MUSIC PLAYING]
MOLLY BLOOM: If you want this very delicious, totally refreshing recipe, you can head to our website, brainson.org.
NANTINE: Sounds scrumptious. And for more top-notch recipes, sign up for the America's Test Kitchen Kids newsletter. You'll get ideas for meals and hands-on activities straight to your inbox.
MOLLY BLOOM: Go to americastestkitchen.com/kids to sign up. You'll be the very first on your block to learn all about ATK Kids, which launches this fall.
NANTINE: It's the perfect way to excite the next generation of curious cookers and engaged eaters.
[KIDS SHOUTING "BRAINS ON"]
MOLLY BLOOM: And speaking of engaged, let's engage those eardrums. Fire up your critical thinking. It's time for the mystery sound.
[MYSTERIOUS SOUNDS]
GIRL: (WHISPERING) Mystery sound.
MOLLY BLOOM: Here it is.
[CRACKLING]
OK, any guesses, Nantine?
NANTINE: It sounds like something's getting cut through.
MOLLY BLOOM: Mhm. Any guesses what that thing might be?
NANTINE: Bread.
MOLLY BLOOM: Excellent thought. All right, we are going to be back with the answer later in the show.
[MUSIC PLAYING]
NANTINE: Do you have a mystery sound you'd like to share with us?
MOLLY BLOOM: A cooking question you want answered on the show?
NANTINE: Or maybe a drawing of Sanden's Lukewarminator or Marc's traveling kitchen.
MOLLY BLOOM: Share it all with us. Just head to brainson.org/contact. Your mail always makes our day.
NANTINE: We're also looking for your answers to this question.
MOLLY BLOOM: If aliens came to Earth and you could only serve them one dish to represent the food of the planet, what dish would you serve them and why?
NANTINE: Molly, you've been asking everyone else, but now it's your turn to answer. What would you serve the aliens?
MOLLY BLOOM: Oh, man. This is a really hard question. It's hard to know what they eat. Like, what if they don't eat meat? Or, what if they don't even have a mouth? Like, what if they just need to get their nutrients from like a mist? So I guess I would serve them like a soup because it's warm so even if they, like, don't eat the soup, they could inhale the steam coming off of it and maybe get some nutrients that way.
NANTINE: Now thinking about it, because I've kind of been thinking about it over the week--
MOLLY BLOOM: Mhm?
NANTINE: --I would just serve them water.
MOLLY BLOOM: Why?
NANTINE: Because, like, I mean, when they're coming to Earth, they're going to see the water as, like, they get to Earth. And it's like, it's the most diverse thing we have.
MOLLY BLOOM: Well, if aliens do come to Earth, I hope they'll submit some rad mystery sounds to us.
NANTINE: Those would be hard to guess.
MOLLY BLOOM: But those aliens would be the first interplanetary members of the Brains Honor Roll.
NANTINE: Yeah! They'd joined the Earth's finest, like Bronwyn.
BRONWYN: Hello! My name is Bronwyn from Brooklyn, New York. And my question is, why are there holes in Swiss cheese?
MOLLY BLOOM: We'll have an answer during our Moment Of Um at the end of the show, as well as the latest group of earthlings to join the Brains Honor Roll.
NANTINE: Stay tuned.
[MUSIC PLAYING]
GONGADOR: Do you like food?
MOLLY BLOOM: Yes.
GONGADOR: Tired of having to shove entire potato in mouth?
MOLLY BLOOM: Uh.
GONGADOR: Wish head of lettuce was in sizes of bites?
MOLLY BLOOM: Sure, but, I mean, you can just chop it.
GONGADOR: Exactly. Now first time ever, you too can chop food. It's Gongador Teaches You To Chop Food video series. Learn from me, master chopper Gongador. Hi-yah!
MAN: [LABORIOUS EATING] Boy, it sure is hard to bite through this watermelon rind.
GONGADOR: Use patented watermelon chop, and trouble's over. Hi-yah!
[WATERMELON CHOPPING]
MAN: Thanks, Gongador. Now my watermelon is so chopped.
MOLLY BLOOM: Wait, he just smashed it. That's not chopping.
WOMAN: I want to share this cake, but I have no way to make smaller portions.
GONGADOR: Use special pastry chop. Hi-yah!
[CAKE SQUISHING]
WOMAN: Yes! Now there are pieces for everyone.
MOLLY BLOOM: What are you talking about? He just splattered cake everywhere. You'd have to scrape it off the wall.
GONGADOR: If you buy video series now, Gongador will throw in lessons on more amazing chops, like raw chicken chop!
[CHICKEN CHOPPING]
Wet noodle chop!
[NOODLE CHOPPING]
Giant fat of jell-o chop!
[JELL-O CHOPPING]
And legendary world-famous ice cream chop!
[ICE CREAM SQUISHING]
MOLLY BLOOM: Yeah!
MAN: Everyone loves chopped ice cream.
MOLLY BLOOM: No, they don't! That's not a thing! And besides, that's not chopping. The big guy's just punching stuff. Haven't you people ever heard of using a knife?
GONGADOR: Gongador Teaches You To Chop Good video series. Call now. Operators are standing by! Hi-yah!
[METAL CLINK]
MOLLY BLOOM: Don't call. Don't support this lunacy. Please, just use a knife.
NANTINE: You're listening to "Brain On" from American Public Media. I'm Nantine Bah.
MOLLY BLOOM: And I'm Molly Bloom. Today, our minds are sharp, and our knives are sharper as we chop our way through some fascinating cooking science.
NANTINE: We've learned about why sharp knives cut better than dull knives. But how do you make a knife in the first place?
MOLLY BLOOM: Knife-maker Moriah Cowles invited us into her studio, Orchard Steel in Vermont, to show us how it's done.
MORIAH COWLES: OK, forging is the first part of the knife-making process.
[FORGE IGNITING]
Basically to forge, you take a piece of steel and you put it in a forge, which is an oven or a kiln that gets up to 2,000 degrees. It gets really, really hot. So it turns that first red and then orange. So when it's that orange color, it gets soft and it changes the molecular structure in there so that it's a little bit softer. It's sort of hard clay, so that you can hammer it to shape and you can get the piece of steel to the shape you want.
[HAMMERING]
In order to hammer it to shape, I actually have to use the anvil, big heavy piece of steel that has a horn on one side and a flat part on the other. And I use it to put the hot piece of metal on so that I can hammer against something hard to help me shape the steel. So the first part, I'll hammer just the tip of it so that I'm getting to the tip of the knife, and then I'll get the heel, which is the part where the blade reaches the handle, and then I'll flatten it out and create a bevel where the top of the knife or the spine goes from thick to thin. Because I want to start on the thick on the top and get thin towards the edge. I probably heat it up, I don't know, between 10 and 15 times just to go through the whole process of making the knife, so going from a rectangle to a fully-formed knife.
After I forge the basic knife shape, the next part of the process is heat-treating the knife. And it's just a basic process of heating and cooling the knife in order to harden the steel. So the knife starts out in the heat-treating oven, which is about 1,500 degrees. It's like four or five times as hot as a pizza oven. And then I'm taking it out and in less than eight seconds, dunking it into a tank of cold oil. So if you can imagine being like standing by the side of a volcano, and then as quick as you can, jumping into ice cold water, it's sort of like that, and that is called quenching. Then, I grind them with a belt sander to make the edge of the knife sharp.
[BELT SANDING]
And that's where-- I'm doing that by hand so my fingers are passing by like a really fast belt sander, so sandpaper that's moving really fast. And you can imagine that's cutting steel, so if my finger gets in the way, it's going to cut my finger even faster. So I've lost a few fingernails. And I've never caught myself on fire, which is good. [LAUGHS]
You have to be really careful, though. You have to be respectful because it's really elemental. I really like that part of it, actually, because it's just steel, fire, and, like, man power or woman power. [SOFT LAUGH]
[MUSIC PLAYING]
MOLLY BLOOM: Thanks to producer Eric Hileman for heading into the studio with Moriah. Making knives is super cool and super noisy. And speaking of noises, it's time to go back to the mystery sound. We'll see if you've honed your listening skills. Are you ready, Nantine?
NANTINE: Yes.
MOLLY BLOOM: All right, here it is again.
[CRACKLING]
Any new guesses?
NANTINE: It sounds more like something crunchy being crumbled up.
MOLLY BLOOM: Mhm. Here is the answer.
MOLLY BIRNBAUM: So my name is Molly Birnbaum, and I'm the editor-in-chief of America's Test Kitchen Kids. And that was the sound of an onion being peeled.
MOLLY BLOOM: An onion.
NANTINE: Oh.
MOLLY BLOOM: Yeah. So have you peeled an onion before?
NANTINE: No.
MOLLY BLOOM: But you know that sort of like crinkly, outside, papery part of the onion that you take off before you eat it?
NANTINE: Yeah.
MOLLY BLOOM: That's what that sound was. And I have a question. Have you ever been around onions when they're being chopped?
NANTINE: Yes.
MOLLY BLOOM: Do your eyes water?
NANTINE: Yeah.
MOLLY BLOOM: Do you have any tips for avoiding that whole thing?
NANTINE: So I learned this from a video. If you're cutting onions or like garlic or something that'll make your eyes water, just chew gum. Like, I think mint gum is better than like fruit-flavored bubble gum and stuff like that. But if you're chewing gum, preferably mint, it's like-- I don't know how, but it's like your eyes don't water. And I was with my friends in the Harlem Grown office during one of the Saturdays when we were cooking, and we all had gum. So then we tried it, and, like, our eyes didn't water, surprisingly.
MOLLY BLOOM: That is an excellent tip. Well, if you want to find out how onions make you cry, you can listen to our episode called "For Crying Out Loud: All About Tears", and you'll find out all about this very potent vegetable.
[MUSIC PLAYING]
Now, Nantine is a relative knife newbie, but we wanted her to learn from an expert shopper.
NANTINE: Francis Lam is the host of Public Radio show "Splendid Table."
MOLLY BLOOM: He writes and thinks about food a lot. And he's also a very talented, classically-trained chef.
FRANCIS LAM: The way I use a knife now I learned in cooking school, in culinary school, and in restaurant kitchens. But it's not the kind of knife and not the kind of, like, knife usage that I grew up using. I grew up in a Chinese-American home and there, we used big cleavers.
In Western cuisine and French cuisine, you see these chefs, they go in the restaurants and they have a whole knife kit. It's like this ridiculous display of like, well, I've got this 8-inch knife, I've got this 6-inch knife, I've got the 2-inch knife, I've got the 45-inch knife, you know, whatever. And they all have different blades and different sharpness and all that stuff.
And then you go to like even a master Chinese chef-- and like I've got one knife-- the idea is you can do every cut you need to do with that one knife. And it's a big, wide cleaver. I'm not saying one is better than the other, one style is better than the other, or one skill, or one philosophy, or one cuisine is better than the other. But if you think about the fact that one cuisine is talking about, OK, you have all these different tools to do all these different individual tasks versus this other cuisine that's like, I've got one tool and I can do all the same tasks, like that's kind of cool, right? But, Nantine, how comfortable are you with a knife?
NANTINE: For me, it really does depend on the size, because my hands, they're pretty small. As to with a bigger knife, it's not uncomfortable for me, but it's kind of like I have more caution because it's like the middle is what's going inside of what I'm cutting, so it's like I'm kind of cautious not to stab into the cereal box or--
FRANCIS LAM: [LAUGHS]
NANTINE: --the containers.
FRANCIS LAM: Yeah, you're slicing, not stabbing.
NANTINE: What's like your first memory using a knife?
FRANCIS LAM: I think my first memory using a knife was when my auntie came over for like a big family dinner. And she's a really good cook, so she was actually doing a lot of the cooking. I was maybe like 9 years old, 10 years old, something like that. And I was always like-- I always liked to hang out in the kitchen because I'd be like, ooh, is that done? I'm gonna taste that. [LAUGHS] Like, I was just like straight chilling, like never had anything to do. And I remember her saying to me, hey, do you want to peel this carrot, and then asking me, hey, do you want to help me cut the carrot? And that was, I think, the first time I was ever asked to use a knife and I remember that. And I remember thinking, I feel so old right now. I feel like such a grown up right now.
NANTINE: Does it matter how you chop up the food you're going to cook?
FRANCIS LAM: I think it matters depending on what you're trying to cook and what kind of effect you're trying to get. For me, like, different shapes don't necessarily matter as much, although they can. That's like my old chef yelling at me again. Like, no, this has to be a perfect circle, this has to be a perfect rectangle, this has to be a perfect square. And part of that is for presentation. But even beyond presentation, size actually does matter when you cut, and surface area matters when you cut. If you're exposing more sides of the inside and you're frying it or cooking in a pan and you want to get it brown and delicious and caramelized, more sides means more browning, means more crispy, means more tasty. But if you're cooking a soup and you just drop in a whole carrot in the soup and you're going to cook it for like an hour or two hours, all that flavor is going to come out of the carrot anyway. It doesn't really matter how you cut it.
NANTINE: Do all kinds of cooking use knives or are there other ways to break up food and, like, release the flavor?
FRANCIS LAM: Oh, that's a good question. I think most cuisines and most cultures do use knives. I think a lot of them use them differently. But I think if you're talking about not using knives, there are times when I know chefs too who say like, no, don't use a knife because that's too sharp and you want to rip something instead, like an herb, maybe. You want to rip an herb instead of cutting it. And what ripping something does is if you think about like a leaf of an herb, and that herb is going to be made of cells. And inside those cells are all the aromas and all the good stuff that's in that herb.
And if you cut it with a knife and the knife is sharp, then you're just kind of cutting it really cleanly and you're not releasing that much versus if you rip it and tear it or maybe like bunch it up and crush it a little bit, then you're actually kind of breaking open a whole lot of those cells and you're releasing all those flavors and releasing all those aromas. So there are times when you don't want to use a knife and times when you do want to use a knife, and a lot of it is kind of like living and learning and trying things out.
NANTINE: Bye, Francis. Thank you.
FRANCIS LAM: [LAUGHS] Thanks, Nantine. It was great to talk with you.
NANTINE: Oh, great to talk with you too.
[MUSIC PLAYING]
Chopping up your food is an important step in cooking, but there's more than one right way to do it.
MOLLY BLOOM: Just make sure you do it safely.
NANTINE: There's a lot of art and science that goes into shaping metal into a knife.
MOLLY BLOOM: And when you cut something, it's really electromagnetic forces pushing apart the molecules.
NANTINE: And your knife and the food you're cutting never really touch at all.
MOLLY BLOOM: That's it for this episode of "Brains On".
NANTINE: "Brains On" is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: We couldn't have made this series without our friends at America's Test Kitchen, Molly Birnbaum, Kaitlin Keleher, Sasha Marx, Tucker Shaw, and Lisa McManus.
NANTINE: And we had production help this week from Lauren Dee, Emily Allen, and Jacqueline Kim.
MOLLY BLOOM: Many thanks to [INAUDIBLE], John Miller, Tony Hillary, Julie Williams, Michelle Faust, Jon Raby, Jennifer Miller, Elyssa Dudley, and Matthew Bynum. And we had engineering help from Veronica Rodriguez, John Miller, and Sara [INAUDIBLE].
NANTINE: Now before we go, it's time for our Moment of Um.
[VARIOUS VOICES SAYING "UM"]
GIRL: Why are there holes in Swiss cheese?
[MUSIC PLAYING]
JENNY EASTWOOD: My name is Jenny Eastwood. And my company is called Smallgoods. I am what is known as a cheese monger. A cheese monger is one who sells cheese. Swiss cheese has holes because of little gas explosions caused by very tiny, very healthy microbes.
So what are microbes? Well, microbes are very tiny organisms that can only be seen under a microscope. Microbes live in cheese, happily munching away on the sugar and fat within that cheese. And just like people, all that food makes them full of gas. Because these microbes live inside the cheese, this gas, known as carbon dioxide, is trapped and it blows up like a balloon. When these balloons pop, they create holes or eyes, as we cheese mongers call them.
MOLLY BLOOM: I'm feeling super cheesy with emotion as I prepare to read through this list of names. This is the most recent group to join the Brains Honor Roll. These are the amazing listeners who send us their questions, ideas, mystery sounds, drawings, and energy to keep our show going. Here they are.
[MUSIC PLAYING]
[LISTING HONOR ROLL]
(SINGING) Brains Honor Roll. Bye-bye.
NANTINE: If you want to be on the Brains Honor Roll, it's easy.
MOLLY BLOOM: Just send your questions, mystery sounds, ideas, or drawings to us by visiting brainson.org/contact.
NANTINE: And you can listen to the rest of the series at our website, brainson.org, or wherever you get your podcasts.
MOLLY BLOOM: We'll be back soon with another helping of culinary science.
NANTINE: Thanks for listening.
GIRL: "Brains On" is supported in part by a grant from the National Science Foundation.
[ELEVATOR DING AND ELEVATOR OPENING]
ELEVATOR: This is Brains On headquarters. Where can I take you?
NANTINE: Hey, Elevator.
MOLLY BLOOM: Elevator, take us to the Brains On lab or kitchen.
NANTINE: Lab or kitchen?
MOLLY BLOOM: I'm so excited for you to see this. It's part lab, part kitchen. It's where we make food, but you know us. We always have some new idea we're trying to work out.
ELEVATOR: Here we are, Brains On lab or kitchen. Goggles on. Taste buds ready.
MOLLY BLOOM: Thanks, Elevator.
SANDEN TOTTEN: Hey, Nantine. Hey, Molly. You guys, come over here. You got to see this.
MOLLY BLOOM: What have you got there, Sanded?
SANDEN TOTTEN: I have been tinkering for months, and I finally got it working. Here it is. Dun, dun, dun, ah, the Lukewarmanator.
[BELLS CHIMING]
NANTINE: It's so sparkly?
SANDEN TOTTEN: Huh? Oh, uh, yeah, I dropped a bunch of parts in that vat of glitter downstairs by accident. But, look. You take this super hot soup that's been bubbling away on the stove for an hour.
NANTINE: [SNIFFS] It smells so good.
SANDEN TOTTEN: Yeah, but way too hot to eat, so I put it in the Lukewarminator, press this button, and--
[RINGING]
[DING AND DOOR OPENING]
Go ahead, try it now. Try it, try it.
MOLLY BLOOM: [SIPS] Oh, my gosh, it's not hot at all anymore.
[SIPS]
And it's not too cold either.
SANDEN TOTTEN: Exactly. It's perfectly lukewarm, the best temperature in the world. I can put in ice water or frozen peas, and voila, lukewarm water, lukewarm peas. Genius, right?
MOLLY BLOOM: You will never burn your tongue again.
[CLATTERING]
MARC: Ah, look out!
NANTINE: What's going on back there?
SANDEN TOTTEN: Oh, uh, that's Marc. He's working on his traveling kitchen idea?
MOLLY BLOOM: It looks like he's just wearing a jumpsuit with a blender taped on one arm and a toaster taped to his back.
SANDEN TOTTEN: Yeah, it's a work-in-progress.
MARC: Hey, Sanden, can I get your help? The toast is ready, but I can't reach it!
SANDEN TOTTEN: Coming, Marc. Uh, I'll see you guys later. I'm going to go help with that.
NANTINE: We'd better head to the studio anyway.
[ELEVATOR DING]
ELEVATOR: I can take you there, but don't you want to try anti-gravity mode first or visit a spork factory?
MOLLY BLOOM: Thanks, Elevator, but we're good.
ELEVATOR: Fine, studio it is.
[MUSIC PLAYING]
(SINGING) Chill, chop, mix, heat. Reverse the order, then repeat. Eat, mix, chop, chill the recipe for every meal.
[SNAPPING]
[CRUNCHING]
[SODA POURING]
Chill, chop, mix, heat. Reverse the order, then repeat. Heat, mix, chop, chill the recipe for every meal.
[ICE IN GLASS]
MOLLY BLOOM: You're listening to "Brains On" from American Public Media. I'm Molly Bloom, and my co-host for our series on the Science of Cooking is Nantine Bah from New York City. Hi, Nantine.
NANTINE: Hi.
MOLLY BLOOM: So, Nantine, you are part of a program called Harlem Grown, where you learn about growing and cooking your own food. Can you tell us a little bit about the Harlem Grown garden? What kind of vegetables and fruits do you grow in the garden?
NANTINE: We grow a lot of herbs. Like, we grow parsley, sage, basil, dill. We also grow cucumbers and tomatoes, swiss chard. Collard greens, we grow those too.
MOLLY BLOOM: So when did you start using a knife for cooking?
NANTINE: Second grade because my after school had like a cooking activity. Like, there'd be a cooking teacher, and she would teach us how to make basic things like yogurt parfaits and stuff. And they also took us to Columbia University for some cooking classes.
MOLLY BLOOM: Cool. When you first started using a knife, were you nervous about it or were you like, let's do this?
NANTINE: I wasn't really nervous because it was a plastic knife, so it was like-- I was like, I can't cut myself with this.
MOLLY BLOOM: So what tips do you have for kids who might not have started using knives yet and might feel a little nervous about it?
NANTINE: Don't use a knife that looks dangerous because you're going to get scared, you're going to start overthinking it, and you might end up cutting yourself in the process.
MOLLY BLOOM: So start with like a smaller, more manageable knife for your smaller hands?
NANTINE: Yeah.
MOLLY BLOOM: Good tip.
[MUSIC PLAYING]
We are very lucky, because Nantine is not the only culinary expert helping us out with this series. We've partnered with the brilliant minds at America's Test Kitchen to answer your many food-related queries.
NANTINE: So far, we've tackled your questions on chilling and heating the stuff we eat.
MOLLY BLOOM: This week, our knives are drawn and we're ready to chop.
NANTINE: We're starting with this question.
BEN: Hi, my name is Ben. And I live in Ventura, California. My question is, why do things that are thinner cut better than things that are lighter?
MOLLY BLOOM: Yeah, why is it you can slice so nice with a thin blade but if you use something wider, like a rolling pin, you just smush it? Brains On producer Sanden Totten is here with an answer.
[DOOR OPENS]
SANDEN TOTTEN: Hey, guys. I just made the most amazing lukewarm latte. [SIPS] Ah. All right, I'm ready to answer this question. But first, we need to understand a little bit more about how knives slice. Let's start with this knife and this carrot.
[CHOPPING SOUNDS]
Chopping it seems like no big drama, right?
NANTINE: I would say there is zero drama happening right now.
SANDEN TOTTEN: Yeah, I used to think that too, then I called up Julia Majors with the American Institute of Physics, and she set me straight.
JULIA MAJORS: Well, it's fascinating at all levels. When you're actually just making a basic cut, you are using forces of materials that are pushing against each other. And at that point of contact, then you have kind of a battle of one material over the other.
[DRUM BEATING]
MOLLY BLOOM: All right, soldiers, that knife is trying to tear our carrot army apart. Will we let it?
GROUP: No!
MOLLY BLOOM: That knife thinks we're weak. Are we weak?
GROUP: No!
MOLLY BLOOM: That knife wants to chop us up and put us in a salad. Are we a salad?
[AGREEING]
MAN: I think we'd be good.
WOMAN: Yeah, totally.
MAN: Yeah, let's do it.
SANDEN TOTTEN: Let's look a little closer at what's going on. Uh, where's Marc's zoom ray? Let me see.
[CLATTERING]
NANTINE: Zoom ray?
MOLLY BLOOM: It's something Marc put together a while back, but don't worry, it works way better than the traveling kitchen.
NANTINE: Phew.
SANDEN TOTTEN: Yes, I found it. So let's zoom in on this carrot knife battle.
VOICE: Zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom, zoom.
SANDEN TOTTEN: Both carrots and knives are made up of these things called molecules.
MOLLY BLOOM: Yes, everything is made up of molecules, they're the building blocks of the universe.
SANDEN TOTTEN: Totally, totally. Now, if we zoom in on a specific molecule--
VOICES: Zoom.
[MUSIC PLAYING]
SANDEN TOTTEN: --we see it's made up of even smaller parts called atoms.
NANTINE: Whoa. Those atoms have a center and then some kind of weird cloud around them. What is that?
SANDEN TOTTEN: Those are clouds of electrons. Electrons are these itsy, bitsy, tiny, winey buzzing little particles that help make up atoms. They're negatively charged and super fascinating. Julia Majors told me that it's here at the level of the electron cloud that the cutting actually happens.
JULIA MAJORS: You're going to have that cloud of electronic charge right at the edge of that carrot material. And then, you're going to have another cloud of the electron charge around the metal. And when they approach each other, then you're going to have, at the end of the day, its electromagnetic forces on that microscopic level.
SANDEN TOTTEN: Both the carrot's electron clouds and the knife's electron clouds are negatively charged. And remember, opposites attract, but samesies push awaysees, so that means these two negatively charged clouds are going to push each other away, kind of like how two similar sides of a magnet push each other away.
[MECHANICAL ECHO]
MAN: Come on, Team Knife, let's shove these carrot clouds out of the way.
MOLLY BLOOM: [GRUNTS] Stand your ground, carrots. Hold tight. Push right back.
SANDEN TOTTEN: Now, to answer Benjamin's question, here is why a sharp, narrow blade is better than a wide, flat one. See, when you're pushing down on the knife, you are applying pressure. The narrower and sharper the edge of the knife, the smaller an area the force of the knife goes to, leading to more pressure for the same effort.
If you have a wide, flat edge, the force is spread out over a large area, so the pressure is weaker overall. You don't want that because you're going to need all the force you can get to break apart that carrot. And since the forces that hold the metal molecules of the knife together are stronger than the forces holding the carrot molecules together, that carrot has a really tough time with a sharp knife.
MOLLY BLOOM: Come on, Team Carrot, keep it together!
MAN: Push harder, knife atoms. [HEAVY EXHALE] We're almost there.
JULIA MAJORS: At some point, that material is going to break apart, so that part of the carrot goes on one side and part of the carrot goes on the other side of where they meet.
MOLLY BLOOM: I slipped. I lost our grip. Oh, no!
[RUMBLING]
MAN: Yes, knives did it! Coming through. Ha, ha! Move out of the way, carrot heads. [CHUCKLES]
SANDEN TOTTEN: So when you cut something, you're not splitting carrot atoms, per se, but you are pushing them away from other carrot atoms that make up carrot molecules and carrot cells with the knife. And it gets even weirder. These carrot and knife atoms push each other away with electromagnetic force, which means they never actually touch each other at all.
MOLLY BLOOM: What?
SANDEN TOTTEN: I know, right? So the knife moves forward, and the carrot molecules part around it, leaving the path wide open for the blade.
MOLLY BLOOM: OK, you are blowing my mind right now. So when I cut something with a knife, the knife and the thing never actually touch?
SANDEN TOTTEN: Nope.
JULIA MAJORS: And that's true of anything that you touch. Even though you feel it and you feel that touch, when you look really, really at the very interface of your hand and the surface, it's actually not fully, fully touching because of those opposing charges.
NANTINE: So I'm not actually touching this table right now?
SANDEN TOTTEN: Nope. You're just feeling electrons repelling other electrons.
MOLLY BLOOM: So when I sit in this chair?
SANDEN TOTTEN: Just clouds of butt molecules hovering over chair molecules, Molly.
NANTINE: This is too much.
SANDEN TOTTEN: Yeah, science can totally mess up your mind, but it will give you something really cool to think about next time you chop a carrot.
MOLLY BLOOM: Thanks, Sanden.
NANTINE: Yeah, thanks.
SANDEN TOTTEN: No problem. Now, if you'll excuse me, this latte got a little too cold while we were talking, so I'm going to go re-lukewarminate it. See you guys.
[MUSIC PLAYING]
MOLLY BLOOM: It's always important to be careful when using a knife. They can do serious damage, even with the mind-blowing physics we just talked about. But here's a safety tip that might be surprising.
SASHA MARX: A sharp knife is actually way, way safer than a dull one.
MOLLY BLOOM: That's Sasha Marx, an editor with America's Test Kitchen Kids.
NANTINE: Dull knives may be more dangerous because you have to push down harder to use them.
MOLLY BLOOM: And that could lead to your knife slipping and cutting you instead of the food. Nantine, what is your favorite knife to use?
NANTINE: A small knife.
MOLLY BLOOM: How do you use it? Do you chop quickly? Do you chop carefully? What is your style?
NANTINE: I chop carefully.
MOLLY BLOOM: Excellent. Always good to be careful. My favorite knife is a serrated knife, those ones that look like little saws that are good for cutting tomatoes or crusty breads. And our friends at America's Test Kitchen Kids shared a great recipe with us for you to practice your knife skills. It's a peach tomato salad, perfect for summer. Here's Molly Birnbaum from America's Test Kitchen Kids.
MOLLY BIRNBAUM: We are chopping and we're using two different types of knives which really gets at how knives behave and which is best for which different type of ingredient, as well as using our hands to tear apart some other types of ingredients.
[MUSIC PLAYING]
MOLLY BLOOM: If you want this very delicious, totally refreshing recipe, you can head to our website, brainson.org.
NANTINE: Sounds scrumptious. And for more top-notch recipes, sign up for the America's Test Kitchen Kids newsletter. You'll get ideas for meals and hands-on activities straight to your inbox.
MOLLY BLOOM: Go to americastestkitchen.com/kids to sign up. You'll be the very first on your block to learn all about ATK Kids, which launches this fall.
NANTINE: It's the perfect way to excite the next generation of curious cookers and engaged eaters.
[KIDS SHOUTING "BRAINS ON"]
MOLLY BLOOM: And speaking of engaged, let's engage those eardrums. Fire up your critical thinking. It's time for the mystery sound.
[MYSTERIOUS SOUNDS]
GIRL: (WHISPERING) Mystery sound.
MOLLY BLOOM: Here it is.
[CRACKLING]
OK, any guesses, Nantine?
NANTINE: It sounds like something's getting cut through.
MOLLY BLOOM: Mhm. Any guesses what that thing might be?
NANTINE: Bread.
MOLLY BLOOM: Excellent thought. All right, we are going to be back with the answer later in the show.
[MUSIC PLAYING]
NANTINE: Do you have a mystery sound you'd like to share with us?
MOLLY BLOOM: A cooking question you want answered on the show?
NANTINE: Or maybe a drawing of Sanden's Lukewarminator or Marc's traveling kitchen.
MOLLY BLOOM: Share it all with us. Just head to brainson.org/contact. Your mail always makes our day.
NANTINE: We're also looking for your answers to this question.
MOLLY BLOOM: If aliens came to Earth and you could only serve them one dish to represent the food of the planet, what dish would you serve them and why?
NANTINE: Molly, you've been asking everyone else, but now it's your turn to answer. What would you serve the aliens?
MOLLY BLOOM: Oh, man. This is a really hard question. It's hard to know what they eat. Like, what if they don't eat meat? Or, what if they don't even have a mouth? Like, what if they just need to get their nutrients from like a mist? So I guess I would serve them like a soup because it's warm so even if they, like, don't eat the soup, they could inhale the steam coming off of it and maybe get some nutrients that way.
NANTINE: Now thinking about it, because I've kind of been thinking about it over the week--
MOLLY BLOOM: Mhm?
NANTINE: --I would just serve them water.
MOLLY BLOOM: Why?
NANTINE: Because, like, I mean, when they're coming to Earth, they're going to see the water as, like, they get to Earth. And it's like, it's the most diverse thing we have.
MOLLY BLOOM: Well, if aliens do come to Earth, I hope they'll submit some rad mystery sounds to us.
NANTINE: Those would be hard to guess.
MOLLY BLOOM: But those aliens would be the first interplanetary members of the Brains Honor Roll.
NANTINE: Yeah! They'd joined the Earth's finest, like Bronwyn.
BRONWYN: Hello! My name is Bronwyn from Brooklyn, New York. And my question is, why are there holes in Swiss cheese?
MOLLY BLOOM: We'll have an answer during our Moment Of Um at the end of the show, as well as the latest group of earthlings to join the Brains Honor Roll.
NANTINE: Stay tuned.
[MUSIC PLAYING]
GONGADOR: Do you like food?
MOLLY BLOOM: Yes.
GONGADOR: Tired of having to shove entire potato in mouth?
MOLLY BLOOM: Uh.
GONGADOR: Wish head of lettuce was in sizes of bites?
MOLLY BLOOM: Sure, but, I mean, you can just chop it.
GONGADOR: Exactly. Now first time ever, you too can chop food. It's Gongador Teaches You To Chop Food video series. Learn from me, master chopper Gongador. Hi-yah!
MAN: [LABORIOUS EATING] Boy, it sure is hard to bite through this watermelon rind.
GONGADOR: Use patented watermelon chop, and trouble's over. Hi-yah!
[WATERMELON CHOPPING]
MAN: Thanks, Gongador. Now my watermelon is so chopped.
MOLLY BLOOM: Wait, he just smashed it. That's not chopping.
WOMAN: I want to share this cake, but I have no way to make smaller portions.
GONGADOR: Use special pastry chop. Hi-yah!
[CAKE SQUISHING]
WOMAN: Yes! Now there are pieces for everyone.
MOLLY BLOOM: What are you talking about? He just splattered cake everywhere. You'd have to scrape it off the wall.
GONGADOR: If you buy video series now, Gongador will throw in lessons on more amazing chops, like raw chicken chop!
[CHICKEN CHOPPING]
Wet noodle chop!
[NOODLE CHOPPING]
Giant fat of jell-o chop!
[JELL-O CHOPPING]
And legendary world-famous ice cream chop!
[ICE CREAM SQUISHING]
MOLLY BLOOM: Yeah!
MAN: Everyone loves chopped ice cream.
MOLLY BLOOM: No, they don't! That's not a thing! And besides, that's not chopping. The big guy's just punching stuff. Haven't you people ever heard of using a knife?
GONGADOR: Gongador Teaches You To Chop Good video series. Call now. Operators are standing by! Hi-yah!
[METAL CLINK]
MOLLY BLOOM: Don't call. Don't support this lunacy. Please, just use a knife.
NANTINE: You're listening to "Brain On" from American Public Media. I'm Nantine Bah.
MOLLY BLOOM: And I'm Molly Bloom. Today, our minds are sharp, and our knives are sharper as we chop our way through some fascinating cooking science.
NANTINE: We've learned about why sharp knives cut better than dull knives. But how do you make a knife in the first place?
MOLLY BLOOM: Knife-maker Moriah Cowles invited us into her studio, Orchard Steel in Vermont, to show us how it's done.
MORIAH COWLES: OK, forging is the first part of the knife-making process.
[FORGE IGNITING]
Basically to forge, you take a piece of steel and you put it in a forge, which is an oven or a kiln that gets up to 2,000 degrees. It gets really, really hot. So it turns that first red and then orange. So when it's that orange color, it gets soft and it changes the molecular structure in there so that it's a little bit softer. It's sort of hard clay, so that you can hammer it to shape and you can get the piece of steel to the shape you want.
[HAMMERING]
In order to hammer it to shape, I actually have to use the anvil, big heavy piece of steel that has a horn on one side and a flat part on the other. And I use it to put the hot piece of metal on so that I can hammer against something hard to help me shape the steel. So the first part, I'll hammer just the tip of it so that I'm getting to the tip of the knife, and then I'll get the heel, which is the part where the blade reaches the handle, and then I'll flatten it out and create a bevel where the top of the knife or the spine goes from thick to thin. Because I want to start on the thick on the top and get thin towards the edge. I probably heat it up, I don't know, between 10 and 15 times just to go through the whole process of making the knife, so going from a rectangle to a fully-formed knife.
After I forge the basic knife shape, the next part of the process is heat-treating the knife. And it's just a basic process of heating and cooling the knife in order to harden the steel. So the knife starts out in the heat-treating oven, which is about 1,500 degrees. It's like four or five times as hot as a pizza oven. And then I'm taking it out and in less than eight seconds, dunking it into a tank of cold oil. So if you can imagine being like standing by the side of a volcano, and then as quick as you can, jumping into ice cold water, it's sort of like that, and that is called quenching. Then, I grind them with a belt sander to make the edge of the knife sharp.
[BELT SANDING]
And that's where-- I'm doing that by hand so my fingers are passing by like a really fast belt sander, so sandpaper that's moving really fast. And you can imagine that's cutting steel, so if my finger gets in the way, it's going to cut my finger even faster. So I've lost a few fingernails. And I've never caught myself on fire, which is good. [LAUGHS]
You have to be really careful, though. You have to be respectful because it's really elemental. I really like that part of it, actually, because it's just steel, fire, and, like, man power or woman power. [SOFT LAUGH]
[MUSIC PLAYING]
MOLLY BLOOM: Thanks to producer Eric Hileman for heading into the studio with Moriah. Making knives is super cool and super noisy. And speaking of noises, it's time to go back to the mystery sound. We'll see if you've honed your listening skills. Are you ready, Nantine?
NANTINE: Yes.
MOLLY BLOOM: All right, here it is again.
[CRACKLING]
Any new guesses?
NANTINE: It sounds more like something crunchy being crumbled up.
MOLLY BLOOM: Mhm. Here is the answer.
MOLLY BIRNBAUM: So my name is Molly Birnbaum, and I'm the editor-in-chief of America's Test Kitchen Kids. And that was the sound of an onion being peeled.
MOLLY BLOOM: An onion.
NANTINE: Oh.
MOLLY BLOOM: Yeah. So have you peeled an onion before?
NANTINE: No.
MOLLY BLOOM: But you know that sort of like crinkly, outside, papery part of the onion that you take off before you eat it?
NANTINE: Yeah.
MOLLY BLOOM: That's what that sound was. And I have a question. Have you ever been around onions when they're being chopped?
NANTINE: Yes.
MOLLY BLOOM: Do your eyes water?
NANTINE: Yeah.
MOLLY BLOOM: Do you have any tips for avoiding that whole thing?
NANTINE: So I learned this from a video. If you're cutting onions or like garlic or something that'll make your eyes water, just chew gum. Like, I think mint gum is better than like fruit-flavored bubble gum and stuff like that. But if you're chewing gum, preferably mint, it's like-- I don't know how, but it's like your eyes don't water. And I was with my friends in the Harlem Grown office during one of the Saturdays when we were cooking, and we all had gum. So then we tried it, and, like, our eyes didn't water, surprisingly.
MOLLY BLOOM: That is an excellent tip. Well, if you want to find out how onions make you cry, you can listen to our episode called "For Crying Out Loud: All About Tears", and you'll find out all about this very potent vegetable.
[MUSIC PLAYING]
Now, Nantine is a relative knife newbie, but we wanted her to learn from an expert shopper.
NANTINE: Francis Lam is the host of Public Radio show "Splendid Table."
MOLLY BLOOM: He writes and thinks about food a lot. And he's also a very talented, classically-trained chef.
FRANCIS LAM: The way I use a knife now I learned in cooking school, in culinary school, and in restaurant kitchens. But it's not the kind of knife and not the kind of, like, knife usage that I grew up using. I grew up in a Chinese-American home and there, we used big cleavers.
In Western cuisine and French cuisine, you see these chefs, they go in the restaurants and they have a whole knife kit. It's like this ridiculous display of like, well, I've got this 8-inch knife, I've got this 6-inch knife, I've got the 2-inch knife, I've got the 45-inch knife, you know, whatever. And they all have different blades and different sharpness and all that stuff.
And then you go to like even a master Chinese chef-- and like I've got one knife-- the idea is you can do every cut you need to do with that one knife. And it's a big, wide cleaver. I'm not saying one is better than the other, one style is better than the other, or one skill, or one philosophy, or one cuisine is better than the other. But if you think about the fact that one cuisine is talking about, OK, you have all these different tools to do all these different individual tasks versus this other cuisine that's like, I've got one tool and I can do all the same tasks, like that's kind of cool, right? But, Nantine, how comfortable are you with a knife?
NANTINE: For me, it really does depend on the size, because my hands, they're pretty small. As to with a bigger knife, it's not uncomfortable for me, but it's kind of like I have more caution because it's like the middle is what's going inside of what I'm cutting, so it's like I'm kind of cautious not to stab into the cereal box or--
FRANCIS LAM: [LAUGHS]
NANTINE: --the containers.
FRANCIS LAM: Yeah, you're slicing, not stabbing.
NANTINE: What's like your first memory using a knife?
FRANCIS LAM: I think my first memory using a knife was when my auntie came over for like a big family dinner. And she's a really good cook, so she was actually doing a lot of the cooking. I was maybe like 9 years old, 10 years old, something like that. And I was always like-- I always liked to hang out in the kitchen because I'd be like, ooh, is that done? I'm gonna taste that. [LAUGHS] Like, I was just like straight chilling, like never had anything to do. And I remember her saying to me, hey, do you want to peel this carrot, and then asking me, hey, do you want to help me cut the carrot? And that was, I think, the first time I was ever asked to use a knife and I remember that. And I remember thinking, I feel so old right now. I feel like such a grown up right now.
NANTINE: Does it matter how you chop up the food you're going to cook?
FRANCIS LAM: I think it matters depending on what you're trying to cook and what kind of effect you're trying to get. For me, like, different shapes don't necessarily matter as much, although they can. That's like my old chef yelling at me again. Like, no, this has to be a perfect circle, this has to be a perfect rectangle, this has to be a perfect square. And part of that is for presentation. But even beyond presentation, size actually does matter when you cut, and surface area matters when you cut. If you're exposing more sides of the inside and you're frying it or cooking in a pan and you want to get it brown and delicious and caramelized, more sides means more browning, means more crispy, means more tasty. But if you're cooking a soup and you just drop in a whole carrot in the soup and you're going to cook it for like an hour or two hours, all that flavor is going to come out of the carrot anyway. It doesn't really matter how you cut it.
NANTINE: Do all kinds of cooking use knives or are there other ways to break up food and, like, release the flavor?
FRANCIS LAM: Oh, that's a good question. I think most cuisines and most cultures do use knives. I think a lot of them use them differently. But I think if you're talking about not using knives, there are times when I know chefs too who say like, no, don't use a knife because that's too sharp and you want to rip something instead, like an herb, maybe. You want to rip an herb instead of cutting it. And what ripping something does is if you think about like a leaf of an herb, and that herb is going to be made of cells. And inside those cells are all the aromas and all the good stuff that's in that herb.
And if you cut it with a knife and the knife is sharp, then you're just kind of cutting it really cleanly and you're not releasing that much versus if you rip it and tear it or maybe like bunch it up and crush it a little bit, then you're actually kind of breaking open a whole lot of those cells and you're releasing all those flavors and releasing all those aromas. So there are times when you don't want to use a knife and times when you do want to use a knife, and a lot of it is kind of like living and learning and trying things out.
NANTINE: Bye, Francis. Thank you.
FRANCIS LAM: [LAUGHS] Thanks, Nantine. It was great to talk with you.
NANTINE: Oh, great to talk with you too.
[MUSIC PLAYING]
Chopping up your food is an important step in cooking, but there's more than one right way to do it.
MOLLY BLOOM: Just make sure you do it safely.
NANTINE: There's a lot of art and science that goes into shaping metal into a knife.
MOLLY BLOOM: And when you cut something, it's really electromagnetic forces pushing apart the molecules.
NANTINE: And your knife and the food you're cutting never really touch at all.
MOLLY BLOOM: That's it for this episode of "Brains On".
NANTINE: "Brains On" is produced by Marc Sanchez, Sanden Totten, and Molly Bloom.
MOLLY BLOOM: We couldn't have made this series without our friends at America's Test Kitchen, Molly Birnbaum, Kaitlin Keleher, Sasha Marx, Tucker Shaw, and Lisa McManus.
NANTINE: And we had production help this week from Lauren Dee, Emily Allen, and Jacqueline Kim.
MOLLY BLOOM: Many thanks to [INAUDIBLE], John Miller, Tony Hillary, Julie Williams, Michelle Faust, Jon Raby, Jennifer Miller, Elyssa Dudley, and Matthew Bynum. And we had engineering help from Veronica Rodriguez, John Miller, and Sara [INAUDIBLE].
NANTINE: Now before we go, it's time for our Moment of Um.
[VARIOUS VOICES SAYING "UM"]
GIRL: Why are there holes in Swiss cheese?
[MUSIC PLAYING]
JENNY EASTWOOD: My name is Jenny Eastwood. And my company is called Smallgoods. I am what is known as a cheese monger. A cheese monger is one who sells cheese. Swiss cheese has holes because of little gas explosions caused by very tiny, very healthy microbes.
So what are microbes? Well, microbes are very tiny organisms that can only be seen under a microscope. Microbes live in cheese, happily munching away on the sugar and fat within that cheese. And just like people, all that food makes them full of gas. Because these microbes live inside the cheese, this gas, known as carbon dioxide, is trapped and it blows up like a balloon. When these balloons pop, they create holes or eyes, as we cheese mongers call them.
MOLLY BLOOM: I'm feeling super cheesy with emotion as I prepare to read through this list of names. This is the most recent group to join the Brains Honor Roll. These are the amazing listeners who send us their questions, ideas, mystery sounds, drawings, and energy to keep our show going. Here they are.
[MUSIC PLAYING]
[LISTING HONOR ROLL]
(SINGING) Brains Honor Roll. Bye-bye.
NANTINE: If you want to be on the Brains Honor Roll, it's easy.
MOLLY BLOOM: Just send your questions, mystery sounds, ideas, or drawings to us by visiting brainson.org/contact.
NANTINE: And you can listen to the rest of the series at our website, brainson.org, or wherever you get your podcasts.
MOLLY BLOOM: We'll be back soon with another helping of culinary science.
NANTINE: Thanks for listening.
Transcription services provided by 3Play Media.
