Glass is a magic thing that is both solid as a wall and clear as the air. It starts out as sand and with tons of heat, and a few key ingredients, it becomes the super useful material we know and love. In this episode we look at how glass is made, why it's clear and how nature makes glass too. Plus, hear about Sanden's latest invention and guess the all new Mystery Sound.
And have you ever noticed little dots on the bottom of a glass bottle or jar? Those are part of a code that the machines can use to sort the containers quickly. Here’s what the numbers and dots mean:
SPEAKER 1: You're listening to "Brains On," where we're serious about being curious.
SPEAKER 2: "Brains On" is supported, in part, by a grant from the National Science Foundation.
SANDEN: Ruby, I have the most amazing idea.
RUBY: OK, lay it on me, Sanden.
SANDEN: You know how, when you're in a room sometimes, it's, like, really dark, and you have to turn on a light and waste electricity just so you can put your hamsters in Victorian outfits to finish filming your adaptation of Jane Austen's "Mansfield Park," starring only hamsters, called "Hams Field Park?"
RUBY: Sort of?
SANDEN: And meanwhile, the sun is out there just literally giving away free light, like some plate of cheese with toothpicks at the grocery store, where you can eat as much as you want, and they can't stop you because it's free sample day.
RUBY: Well, yeah. I mean--
SANDEN: So what if, instead of paying for electricity to light your room, you created a new kind of wall that's still solid, but totally see-through, so all that freaky sunlight comes pouring in, lighting your set and perfectly capturing the complex range of emotions displayed by your lead, Jon Hamster, who is a genius actor, by the way.
SANDEN: Whoa, whoa, whoa, whoa, Sanden, hold on. A transparent wall? I think what you're designing is a--
SANDEN: Then I figured, people would want these clear walls for lots of non-hamster uses, too, like lighting rooms for reading or so plants can grow inside. You could even use them to enjoy the view outside. I could market this to everyone. I'll call them transparent walls.
And I'll sell so many that, soon, there'll be an every house in the world. And people will be like, Sanden Totten is such a genius for inventing the transparent wall. He should be president. And I'll be like, no, I didn't do it for the power. I did it for the money. And I'll make a billion dollars. Genius, right?
RUBY: Sanden, you literally just invented windows. They already exist. Like, there's one right behind you.
SANDEN: Windows? That name will never stick. My idea is much better.
MOLLY: You're listening to "Brains On" from APM Studios. I'm Molly Bloom, and with me today is Fred from Canberra, Australia. Hi, Fred.
FRED: Hi, Molly.
MOLLY: Today, we're talking all things glass, from bottles and windows to computers and cables. Glass is pretty amazing and very useful. I've been wearing glasses since the third grade.
FRED: Imagine trying to read a comic book without those.
MOLLY: Right? Imagine trying to drive to "Brains On" headquarters without a windshield.
FRED: Bugs everywhere. Imagine waking up in the morning and looking at a wall.
MOLLY: Oh, Fred, if you had to come up with a better name for windows, what would you call them?
FRED: I would call them transparent walls.
MOLLY: Nice. I think Sanden had a similar thought for sure. What would you say is the most important glass in your life?
FRED: A drinking glass, so you can drink.
MOLLY: Totally. We need water to survive.
MOLLY: I'm going to say, the most important glass in my life is, probably, my glasses that I wear. Although, I think those might be plastic. So I'm going to change my answer and say the most important glass in my life is my windshield on my car.
FRED: Yeah, that's pretty important.
MOLLY: Yeah, there's a lot of bugs on the highway. And it's hot, and it rains. Yeah, the windshield is very important. Glass is incredible stuff. It's transparent, which means you can see through it--
FRED: --but it's also very strong.
MOLLY: It can be beautiful--
FRED: --but breakable.
MOLLY: And glass totally changed our world. It allows us to correct our vision, like with my glasses.
FRED: We use it to make bottles and jars for preserving food, so we can eat it later.
MOLLY: And glass is a crucial part of microscopes. Without those, we'd probably never know about viruses, bacteria, and other tiny things.
FRED: Glass is also part of telescopes, so glass help expand our view of the universe.
MOLLY: We use it for beads as decoration. Glass can even make music.
[INSTRUMENTAL MUSIC PLAYING]
That's a glass Armonica, an instrument invented by Ben Franklin in the 1700s. It uses rotating glass bowls and water to make mesmerizing sounds.
FRED: So the Armonica is older than the United States?
MOLLY BLOOM: Yeah, humans have been making glass for a long time. Maybe you've heard the term glass blowing. It's a technique that dates back 3,500 years.
KATHRYN: The Roman realized that they could actually take this glassy molten substance and put it at the end of a hollow tube and blow it and inflate it like a balloon. So that's where glass blowing started.
MOLLY: That's Kathryn Aguilar. She knows a lot about glass. She's a science educator at the Corning Museum of Glass in New York.
KATHRYN: Before a glass blowing, they were making core formed vessels, which are basically vessels, where they would take a stick. And the end of the stick would be covered in a core, and the core was made out of, probably, clay, maybe some horse manure, and things like that. And they would dip that core into a pot of molten glass and then let it cool very slowly. And then, they would scrape out the core, and they would be left with a tiny little vessel, maybe, can only hold an ounce or two.
MOLLY: So humans have been making glass for thousands of years. I mean, archeologists have even found solid glass artifacts in King Tut's tomb from ancient Egypt. But nature has been at it even longer. Take obsidian, for example.
FRED: It's a kind of black glass that's made when volcanoes spit out lava, and it cools really quickly.
MOLLY: There are also fulgurite.
FRED: Which is glass made when lightning strikes sand.
KATHRYN: Basically, lightning will strike a beach, and it melts the sand together really, really fast. And then, the lightning goes away. And then, the sand cools really quickly, and it forms a glassy structure.
MOLLY: And then, there are tektites.
FRED: Which are glass pebbles formed by meteor strikes.
MOLLY: One thing volcanoes, lightning, and meteor strikes all have in common is they make a lot of heat, which makes sense, because to form glass, things have to be hot, really hot.
FRED: Yeah, but humans aren't using volcanoes or lightning strikes to make glass. So how are they doing it?
MOLLY: Audrey from Cortland, Nebraska, has the same question.
SPEAKER 3: My question is, how do they make glass?
MOLLY: To find out, I visited three girls at Foci Minnesota Center for Glass Arts, where, as I expected, it was very hot.
SPEAKER 4: I'm a heat person, so I like the heat even though the heat isn't as fun.
MOLLY: Bria and Bryn are sisters who make glass. Bria is into the heat. Bryn, not so much. They're here with their friend, Eliza, who was also learning to work with glass.
SPEAKER 5: You just get really tired, and sweaty, and gross really fast. The glass is surprisingly heavy, but once you get used to it, it's not that heavy.
FRED: Making glass from scratch is not only hot. It's also a bit of a magic trick.
MOLLY: Right. You start with gritty silica sand and, alakazam, turn it into smooth, clear glass. Here's how this glass-tacular magic works. The first step is to heat up the sand and melt it down.
FRED: But it's not like you can put it in a pot on a stove. A glass expert Kathryn says, you have to get the sand much, much hotter than your stove.
KATHRYN: It has a very high melting point. It's close to 4,000 degrees Fahrenheit. That is really difficult to melt in a furnace.
FRED: 4,000 degrees? That's hotter than lava, hotter than the hottest planet in our solar system.
MOLLY: That is very hot. There's a way to lower the melting point of silica sand, so it can melt with less heat. Basically, you add this white powdery stuff called sodium carbonate or soda ash, which is really similar to baking soda, like what you'd put in cookies and cakes. And when you add that into the mix, you only need 2,300 degrees to melt the sand.
FRED: Still hotter than all those things I just said, but just not 4,000 degrees hot.
MOLLY: Right. And it's possible to get a furnace to 2,300 degrees. And at that point, there's just one more thing to add.
KATHRYN: The last ingredient is the limestone. So limestone is another mineral that is mined out of the ground, and it has calcium in it. And the calcium helps the sodium and the silica all stay together. Without the calcium, it would be really unstable. It would be really prone to weathering, and the glass would just deteriorate.
MOLLY: By the way, this kind of glass is called soda lime glass and is the most common kind of glass made today. It also sounds like a delicious drink. I would love a glass of soda lime.
FRED: Make that two.
MOLLY: So how does a mix of minerals that looks like sand presto change-o into smooth, clear glass when you heat it up? Well, picture this. Like everything, the sand is made up of super ultra tiny building blocks called atoms, and those atoms join together to make bigger building blocks called molecules. If you take the "Brains On" zoom ray--
FRED: Got it?
MOLLY: --and you use it to zoom in on these molecules, you'd see they're put together in a very specific and orderly pattern.
FRED: Things with this kind of pattern are called crystals.
SPEAKER 6: That's a crystal.
MOLLY: So before you melt the silica sand, its molecules are in this nice, neat order.
SPEAKER 7: Molecules, line up.
MOLECULES: We're lined, sarge.
MOLLY: But when we start heating that silica sand way up, the invisible bonds between the molecules are broken, and the molecules get all jumbled up.
MOLECULES: It's hot in here.
It's like a furnace.
I want to eat some ice cream.
SPEAKER 7: Get back in line.
MOLECULES: Are you kidding? It's way too hot for that.
We're just going to go about as we please.
SPEAKER 7: Oh, boy, it's hot. You're right. At ease.
MOLECULES: Way ahead of you.
I've been lying down for 5 minutes already.
MOLLY: It's like what happens with ice. The molecules in a solid cube of ice are held together in a very organized pattern. As that ice cube melts, the molecules get jumbled up and become water. But there's a big difference between sand and water. When you refreeze the water, the molecules go back into that organized pattern.
FRED: The sand that makes up glass doesn't do that. When it cools and becomes solid again, the molecules stay all jumbled up.
SPEAKER 7: It's starting to cool down. Back in line, molecules.
MOLECULES: It's way too hot for that.
I don't feel like getting up.
Let's just stay like this.
This is not so bad.
SPEAKER 7: I give up.
MOLLY: When this happens to something, we call it an amorphous solid. Amorphous just means something that doesn't have a set shape. All those teeny molecules get mixed up like they're in a liquid. But in this case, they're staying still like a solid. Chances are, you have a lot of amorphous solids in your house right now, not just glass, but also wax and plastic.
FRED: So that's the magic trick. You take a bunch of gritty powdery stuff and turn it into a smooth, solid glass with help form a little molecular sleight of hand.
MOLLY: But once you've performed this trick, you have to act fast. Remember, Bryn and Bria?
SPEAKER 5: Feels like honey.
SPEAKER 4: I thought I felt like a mush marshmallow. Marshmallow fluff, kind of.
SPEAKER 5: Yeah, it's like that.
MOLLY: They learned in their glassmaking class that, as soon as you have the gooey liquid glass out of the hot furnace, it starts cooling fast. If you wait too long, it becomes too hard to shape. So they have to start working right away.
SPEAKER 8: Brains on.
MOLLY: We're going to find out more about glass in just a minute. But first, it's time for the mystery sound.
SPEAKER 9: Mystery sound.
MOLLY: You're ready, Fred? Got your ears ready?
FRED: Yep. Yes, my ears are ready.
MOLLY: OK, here it is.
What is your guess?
FRED: I think it's someone cleaning windows, like dumping bucket of water on the windows, and then wiping it off.
MOLLY: Oh, that is a really good guess. Yeah, there was like definitely some liquidy sounding noise there. I like that guess.
MOLLY: All right, well, we'll hear it again. You get another chance to guess and then hear the answer right after the credits.
We're working on an episode about our remarkable imaginations, and we want to hear from you. If you've had an imaginary friend, now or in the past, we would love to hear about them. Fred, I'm wondering, have you ever had an imaginary friend?
FRED: One of my friends has.
MOLLY: Oh, yeah? Do you remember what that friend was like, the imaginary friend?
FRED: It was a cat named Bucket.
MOLLY: Oh, nice. So when your friend was talking about Bucket, did you, kind of, play along and also pretend to play with Bucket? Or you're just like, OK, sure. Yeah, Bucket.
FRED: I was like, OK, sure, yeah, Bucket.
MOLLY: Makes sense. Yes, I had an imaginary friend when I was younger, named Mrs. Snail, who was a tiny, tiny snail, who wore a bonnet. I'm not sure where I got that from, but that was my imaginary friend. So listeners, please record yourself, telling us about your imaginary friend, and send it to us at brainson.org/contact. And while you're there, you can send us mystery sounds, drawings, and questions.
FRED: Like this one.
SPEAKER 10: Hi, my name is Steyer. And my question is, why can dogs learn tricks, but cats can't?
MOLLY: Again, that's brainson.org/contact.
FRED: And keep listening.
SANDEN: Are you tired of the outside always getting all that free light from the sun? Do you wish your inside could be brighter and less cave-like? Hi, I'm Sanden Totten, handsome genius inventor behind innovative ideas, like magnetic pants and glow-in-the-dark toast, and now, transpara-walls. They're walls you could see through.
I know what you're thinking. Why not just knock a hole in the wall? Well, when you do that, not only do Mark and Molly yell at you, but it also lets animals and rain inside. But transpara-walls are solid, so nothing gets in except free light. Don't take my word for it. Listen to John Hamster, star of the well-lit movie, "Hams Field Park."
You said it, John. So what are you waiting for? Order your transpara-walls now, and I'll even throw in some glow-in-the-dark toast, for when you really want to eat toast alone in the dark. Call now.
FRED: You're listening to Brains On from APM studios. I'm Fred.
MOLLY: And I'm Molly.
FRED: So Molly, there's been something I've been wondering.
MOLLY: I know. I know. I just realized that I've been wearing my shirt inside out and backwards all day, and I just realized--
FRED: No, no, not that. What I'm wondering is, sand is used to make glass, right? And sand is definitely not clear. So how are we able to see through glass? I sent this question into the show, and you told me you were going to answer it today.
MOLLY: Oh, yes, we are. And I've asked for some help.
VISIBLE LIGHT: Hey, my dudes. Ready to lighten up the mood in here?
FRED: Oh, my eyes. Who are you?
VISIBLE LIGHT: Who am I? Bro, I'm visible light. I'm pretty much the reason you can see, like, anything.
MOLLY: Here, here, Fred, I brought us some sunglasses. Visible Light is going to help me explain this next part.
VISIBLE LIGHT: Yeah, totally, totally. OK, so normally, I'm on my board, hanging 10, and I look like white light. Actually, though, I contain all the different colors. When I hit a solid object, most of me gets absorbed, except for whatever color that object is, which gets bounced back to your eye.
MOLLY: Yeah, like my lucky banana. The atoms inside of it are absorbing every color, except for yellow.
FRED: Why do you have a lucky banana?
MOLLY: So much potassium. And don't think about it too hard. Let's bounce back to Visible Light.
VISIBLE LIGHT: Bouncing back. You got it, dudes. Tubular.
FRED: OK, so what happens with glass?
VISIBLE LIGHT: Right. So this is super rad. Sand and glass are both made up of silica, and neither of them can absorb my energy. Think of it like a lock and key. For me to get absorbed, there needs to be a match, like the right key fitting into the right lock.
Well, glass and sand are like locks that I don't fit in, so I don't get absorbed or bounce back. The difference, though, is that sand has that gnarly crystalline structure so that causes the light to bounce around in all different directions rather than pass clearly through.
FRED: OK. Here, I'll show you. Mind if I borrow that zoom ray?
MOLLY: Not at all.
VISIBLE LIGHT: Thanks. Cowabunga, dudes. Get ready for the huge swell.
FRED: Whoa, what is going on in here? It feels like I'm in a hall of mirrors, but somehow, even more confusing.
VISIBLE LIGHT: You see, the molecules are so tightly packed and so rigidly organized that even though I'm passing through the molecules, I'm getting scattered every which way, but never really getting out. Now, let's surf over to glass.
FRED: Wow, smooth.
VISIBLE LIGHT: Sure, it's smooth. It's also a molecular mess. There are atoms all over the place.
ATOMS: It's not so bad.
Yeah, we just got so hot.
VISIBLE LIGHT: I'm surfing around all of these molecules, but none of the waves are being absorbed or bounced back. The atoms around here just don't vibe with me. Honestly, it's pretty bogus. I'm outie.
MOLLY: Wow, you just passed right through.
FRED: So sand and glass can't absorb any light?
VISIBLE LIGHT: Well, not exactly. They can't absorb any visible light, you know, the light you can see. But there are other forms of light that you can't see. My compadres, ultraviolet light and infrared, do get absorbed. That's why you can stand behind a window without getting totally sunburnt. The light that burns you gets absorbed and blocked.
MOLLY: Really rad. Thanks, Visible Light.
VISIBLE LIGHT: Any time, dudes.
MOLLY: OK, so we've been talking a lot about how to make glass, but we haven't really talked about the cool things you can make out of glass. I visited Kyle Fiebelkorn at the Anchor Glass Factory in Shakopee, Minnesota, to find out how they turn molten glass into bottles and jars. It starts with that very hot furnace.
KYLE: It's hot enough. The one furnace is at 2,860 degrees Fahrenheit on the top side. The other furnace would run about 2,760, 2,770. It's 24/7 operation. I get guys that work around the clock for me, and Christmas is just-- it's just Wednesday.
MOLLY: The molten glass inside the furnaces is almost five feet deep. That's over 300 tons of molten glass or about the same weight as two blue whales. That liquid glass is funneled through small channels that send it to machines, where it's molded or shaped into bottles.
As you can imagine, it takes a lot of energy to make glass from scratch, all that heating and melting. But melting down already-manufactured glass takes a lot less energy. So glass manufacturers, like Anchor like to recycle glass since it makes the process more efficient.
KYLE: It's much glass we can get in from the public. We'll, run it.
MOLLY: Recycled glass and other ingredients help supply their furnace with enough molten glass to feed the bottle and jar-making machines, and those machines are hungry.
KYLE: We have machines that make 400 bottles every minute.
MOLLY: Anchor Glass uses that soda lime mix you heard about earlier. It makes it clear, colorless glass. But you can also add lots of different minerals to the glass to change its color, like iron oxide, which turns the glass green.
FRED: If you want to see glassmaking an action, the Corning Museum of Glass has large streams of glass blowing demonstrations. We'll post a link on our website, brainson.org.
MOLLY: While you're there, you can also see some cool videos of the glass-making machines in action at Anchor Glass, and you can find out what the code at the bottom of glass bottles and jars means.
FRED: And you can watch people playing this thing, the glass Armonica.
MOLLY: So we know glass is all around us-- windows, jars, vases, all sorts of stuff. It's a material that we've been using since ancient times, but it's also very modern. The screens that we watch TV on and used to FaceTime our friends are made of glass. And believe it or not, it's also bringing you high speed internet.
FRED: Yeah, glass is used to make special cables called optical fibers. These are very thin glass cables that power almost all of our modern communication technology. And you might not notice them, but they're everywhere.
ZAHRA: So optical fibers connect the internet, let's say, from here to Europe. So they're running under the bottom of the ocean throughout the whole world, and they're these very tiny wires of glass that have also glass called software polymer glass coatings.
MOLLY: That's Zahra Fakhraai. She's a chemist at the University of Pennsylvania, and she's really into glass. She even has a magnet on her office door that says, glass nerd.
ZAHRA: To me, it's just completely mind-boggling, that we can make thousands of kilometers of glass and not have a single tiny bit of defect in it.
FRED: Scientists are constantly figuring out new ways to use glass for lots of different things, making it incredibly thin, but also super strong. There's even a group that's using tiny glass fibers to heal wounds in our bodies.
MOLLY: So even though glass has been around a long time, it's still got new tricks up its sleeve.
FRED: Glass is made when you melt silica sand and other materials into goo.
MOLLY: You can shape that goo as it cools and make all kinds of stuff with it.
FRED: Once it hardens, glass becomes an amorphous solid.
MOLLY: And it can't absorb light, so we can see right through it.
FRED: We use glass for all kinds of things, from bottles to computers, and we're coming up with newer ways to use it all the time.
MOLLY: That's it for this episode of "Brains On."
FRED: This episode was produced by Molly Bloom, Rosie DuPont, Anna Goldfield, Ruby Guthrie, Mark Sanchez, Anna Weggel, and Nico Gonzalez Wisler.
MOLLY: Our editors are Sanden Totten and Shahla Farzan. This episode was sound design by Rachel Breeze and mixed by Alex Simpson. We had engineering help from Alex Simpson and Mark Jennings. Special thanks to Lisa Bevan. Also thanks to Sam Chu, Nancy Yang, Meg Martin, Peter Cox, Philip McCarty, and Eric Wrangham for sharing their vocal talents. Also, thanks to Kim Guzzo from Anchor Glass and Kelly Nezwrorski from FOCI.
FRED: "Brains On" is a nonprofit public media program. There are lots of ways you can support the show.
MOLLY: Yeah, head to brainson.org. There, you can donate, listen to past episodes, submit questions for future shows, and even get your very own "Brains On" hoodie. OK, Fred, are you ready to hear the mystery sound again?
MOLLY: All right, here it is.
FRED: I still think it's someone washing windows very recklessly by just dumping buckets of water on it.
MOLLY: I think that's a really good guess. I can't think of a better guess than that, so do you want to hear the answer?
FRED: Sure. Let's go.
MOLLY: All right, here it is.
EDGAR: My name is Edgar, and that was the sound of my shower squeegee. I hear it every time when I clean the water droplets off the shower door.
MOLLY: Hey. Fred, that was very close.
FRED: Yeah, I was close.
MOLLY: Yeah, like cleaning the windows with a squeegee? The shower door is made of glass.
FRED: Yeah, close.
MOLLY: Very close. Nice work. Very good ears.
Now, it's time for the brains honor roll. These are the incredible kids who share their mystery sounds, drawings, questions, ideas, and high fives with us. Lucas from Flowery Branch, Georgia Arthur from Woodbury, Minnesota, Denver and Oscar from Bryson City, North Carolina, Martin and Daniel from Hampden, Connecticut, Eric from Bel Air, Maryland, Llewellyn and June from Saint Paul, Minnesota.
Arlo and Ruby from Louisville, Kentucky, Liam from Toronto, Kate and Molly from Mapleton, Illinois, Rosie and Adelita from Albuquerque, New Mexico, Kaylee from Anchorage, Alaska, Sofia from Kampala City, Uganda, Quentin Holden from Rosemount, Minnesota, Arthur and Maxime from Belgium, Elijah and Isaiah from Greensboro, North Carolina.
Aiden from Fairfax, Virginia, Zeke and Zay from Union City, California, Cassidy from Las Vegas, Nevada, Grace from Vancouver, British Columbia, Brandon from Anderson, South Carolina, Shar from Westford, Virginia, Kimmi from Essex Vermont, Karina and Myles from Prairie Village, Kansas, Benjamin and Alana from Washington Township, New Jersey.
Nevan from New Jersey, Finlay and Kennedy from Strongsville, Ohio, Oliver from San Diego, California, Ricky from Simi Valley, California, Ismael from Johannesburg, South Africa, Alina from Lawrence, Kansas, Mia and Angelina from Katy, Texas, Carter and Chase from Lexington, Kentucky Roland and Mikayla from Austin, Texas, Dylan from Baltimore.
Caleb from Cabot Arkansas, Vera from Phoenix, Arizona, Sam from Houston, Texas, Porter from Liberty Lake, Washington, Oliver Finley and Arlo from Reno, Nevada, Amelia, Olivia, and Lucas from Lafayette, Louisiana, Maxwell from Mississauga, Ontario, Owen from Cottage Grove, Oregon, Arlo from Minneapolis, Mia from Miami, Florida, Emily from Rockville, Maryland, Constance from Louisiana, Benny and Cora from Minneapolis. Mason from Saint Louis.
Sophia at Arlo from Geneva, Switzerland, Maya from White Plains, New York, Norah from Denver, Gibson from Bowie, Maryland, Etta and Giles from Rhinebeck, New York, Beatrix from Norwich England, Aiden from Toronto, Owen and Jackson from La Plata, Maryland, Kassie and Caden from Houston, Texas, Ellie from Austin, Texas.
Talia from Houston, Texas Aubrey from Middleton, Colorado, Wyatt and Warren from Calhoun Georgia, Owen from Plantation, Florida, Holland from Florence Massachusetts, Kale and Orion from Ashland, Oregon, Emma from Bogart Georgia, Cambria and Kaylee from Salt Lake City, and Olivia from Elizabethtown, Pennsylvania. We'll be back next week with more answers to your questions.
FRED: Thanks for listening.
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