ABC Listen.
8, 9, 10.
Oh, hi, Nidge here.
And today on Imagine This, I am setting a new personal best.
14, 15.
What are you doing?
I'm trying to keep this soccer ball up.
My record is 25 kicks.
Go faster.
18.
Keep going.
Go, Mitch.
19.
Almost there.
I'm so excited for you.
You're almost there.
Go, Mitch.
Oh, no.
Uh-oh.
Oh, no.
You broke the window.
Oh, my bad.
Oh, you're in trouble.
Oh, stand back.
Broken glass is really sharp.
It's so spiky.
And also, if you step on it, it'll really, really hurt.
Do you think I can fix it?
Not even a super glue.
Hmm.
And then you have to properly clean it up.
Yeah.
A lot of you have been asking about glass.
Hi, my name's Artie and I'm seven years old.
I'm Inara, I'm seven years old.
I'm Jack and I'm seven years old.
My name's Sage and I'm six.
And I'm Odie and I'm five years old.
And we would like to know, how is glass made?
Any ideas?
So maybe they used a special sewing machine.
Maybe they got a big factory.
They smooshed up all the plastic and added the chemicals and made it.
What do you think it's made of?
Crude oil?
Sand.
Special type of sand.
And how do they make it see-through?
A machine.
And it washes the glass and takes out the coloured parts.
Could be.
We should ask Dr Thomas Derrick.
He's an archaeologist.
I think they dig up lots of stuff to figure out what was the past like.
Exactly.
Let's go find him.
Just give me a sec while I get a broom.
Hi, Dr. Derek.
Hello.
Hi.
Oh, hello.
Hello.
How's it going?
What are all those glass bottles?
It's my collection of glass perfume bottles from ancient Rome.
I'm curious about the sensory world of Rome.
That means all the tastes, signs and smells of the past.
Do I have a smell?
There's no perfume left in the bottles, but we can do special tests on them with computers to find out what used to be stored in them.
Cool.
So what does ancient Rome smell like?
Well, the perfumes would have been scented with a mix of flowers, plants and spices, rose petals and lavender and saffron.
That sounds nice.
Mmm, yum.
They helped hide all of the not-so-nice smells that were around then too.
Poot all week?
Yeah, in fact, they used pee to clean clothes.
Ew.
Ew, that's disgusting.
Seriously?
Gross.
Their clothes will never be clean if they used to be.
Glad you study ancient perfume, Tom, and not ancient laundry.
It might sound silly, but being able to make these little glass bottles changed the world forever.
How?
Well, let's imagine ourselves back in time and take a look.
The ancient world?
Actually, ancient Egypt.
Let's head back to the first century CE.
That's about 2,000 years ago.
Wow, this is ancient Egypt?
Where are the pyramids?
About a day's walk that way.
We're at a place called the Wadi el Natroon, just outside Cairo.
It's known for these very special salt lakes.
It doesn't look like much of a lake.
It's not much water.
What's the white stuff?
It's a kind of salt called natron.
This is the region where glass was first made.
Glass is made from this stuff?
What?
How is it made of glass?
It's not see-through.
The ingredients to make glass are a lot of sand, a dash of soda and a little bit of lime.
Sounds like a drink.
It'd be a very dry drink.
Sand, soda and lime are the nicknames for three types of crushed up rock and minerals.
Oh, yeah.
We learned before that sand can be really tiny bits of rock.
Yep, lime is short for limestone, a type of rock that has lots of calcium in it.
Wow, you can find calcium in lots of places.
Find it in your bones, on your teeth.
It's in yogurt and milk.
What's the soda part?
Soda is short for soda ash, natron.
Ah, OK, so you get sand and limestone rock from the desert and soda ash from the salty Natron Lake.
But how do you make these three dry rocky powders turn into glass?
You need things to get hot.
What's this place?
It's called a tank oven.
Great!
What's cooking?
Any pizza?
It's not that kind of oven-ish.
No, a tank oven is a big furnace.
It looks like a little house or shed.
How much glass can it make?
The biggest of them can make 20 tons of glass in one go.
How?
Those dry ingredients we talked about are poured into big flat trays and cooked until they're so hot they melt.
How can you melt sand?
You can melt anything if it's hot enough.
To make glass, you need all of your dry ingredients to cook at over 1,000 degrees Celsius.
In the past, it would have taken days of stoking these fires.
How hot is 1,000 degrees?
My oven at home only goes to 250.
That's super hot.
As hot as lava.
Whoa!
It even looks like lava.
The salt and the limestone gets mixed together with sand.
It's glowing!
It makes it dark orange like fire.
To melt sand just on its own, you'd need much higher temperatures.
The soda ash lowers the melting point of sand.
That means instead of melting at 2000 degrees, it melts at half that temperature, which is still incredibly hot.
What does the limestone do?
It helps the sand and the soda ash mix together nicely.
Otherwise, the sand and the soda try to separate like oil and water.
As the glass cools down, it starts to turn clear and hard.
The Romans made big slabs of glass this way.
To make windows.
Ah, yeah.
Do you reckon I could take one back to fix the one that I broke?
Whoa.
Oh, they just finished making that.
Why are they smashing it up?
Now the glass can be broken up and shipped around the world to be melted again, shaped into all kinds of glass objects.
Glass is endlessly reusable.
Cool.
How do they make it into different shapes?
Must be way too hot to touch.
What do you do when your food's too hot?
Blow on it?
Exactly.
Glass blowing was invented in what we now call Jerusalem.
Just like Egypt, Jerusalem was part of the Roman Empire too, which stretched right across Europe.
They're putting the broken glass in the fire.
It's coming out.
That's not glass.
Melted glass is a runny liquid.
As it cools down, it gets thicker and thicker.
It looks like really thick honey.
Looks delicious.
It's too hot.
Yeah, it's like goopy, glowing, melted marshmallow.
If it cools down too much, it turns back into a solid and you can't bend it into shape anymore.
So glass workers have to move quickly.
Wow, look at them go.
They're pulling it apart with metal tongs.
So stretchy and bendable.
You can make any shape using these special tweezers and tongs.
But the real game changer was this.
Whoa, they're blowing into a metal straw and the glass is blowing up like a balloon.
The blowing to stretch out the glass is so cool.
It looked like a big bubble and he was using his breath to make that big glass bowl.
That's it.
Making glass is tricky.
By blowing air through a metal tube, you can make round objects very quickly.
Bowls, jugs, vases.
Perfume bottles?
Yeah.
It might be something we take for granted now, but having containers with lids, like glass jars, meant that everyday people could store food and medicine.
Yeah, that is a game changer.
And we could put windows in homes, creating safer and brighter living environments.
This is especially useful in places with very cold winters.
Yeah, you could make all kinds of things.
Lips.
Mirrors?
Glasses?
Yeah, I wear glasses sometimes.
It's amazing because we see glass every day.
We literally see right through it.
Yeah, it's easy to forget it's even there.
But glass is a miraculous material.
It's given us a lot.
Even the stars.
What?
Glass is in telescopes and microscopes and basically any major scientific discovery you can think of.
Wow.
They might need a magnifying glass to look at stuff or they can, like they need glass to look through things and to see stuff closer or better.
I might open the screen without the screen is actually glass.
How do we see through it?
That's more of a physics question.
Nish is a physicist.
Ah, well, glasses see through because light can move through it.
The light isn't being absorbed into it, like with wood or rock.
It's also not being reflected away, like with shiny metals or mirrors.
It's clear.
Yeah, it's a really incredible invention.
There's another thing that ancient Romans were great at.
We know it's not laundry.
Recycling.
Really?
How?
They got a giant vacuum cleaner and put everything they could turn into glass under it, and then they sucked all the colour out of it and turned it into glass.
That's a cool idea.
Not quite.
They sorted through their rubbish and separated out the glass.
Then they smashed it up into little pieces and melted it again.
Ready to be turned into something new.
Just like we do it today.
That's great.
Are we going to ever run out of glass?
Even though the world has a lot of sand and limestone and soda ash, these days, we make hundreds of millions of tons of new glass every year.
That's a lot.
That is a lot.
But the great thing is that there's no limit to how much you can recycle and reuse glass.
It won't break down.
You can use it forever and recycle it infinitely.
I did not know that glass could be used and saved technically forever.
That's amazing.
So we'll never run out of glass if we do a better job at recycling.
It's really good for the planet that it doesn't break down.
So if it doesn't break down, all the pieces won't get into the earth.
Plus, recycling uses way less energy than making new glass.
That means we've already made all the glass we'll ever need.
We've just got to recycle it.
We should recycle way more.
Not throw it in the bin.
Thank you so much for showing us how glass is made and remade.
Tom, it's been really clear.
Thank you.
My pleasure.
So Artie Sage Jack, Inara and Odie glass is made by heating up the dry minerals found in sand and rocks.
Sand.
Limestone.
Solar ash.
Until they melt into a red hot liquid.
As it starts to cool, glass turns thick and flexible and can be moulded into any shape.
Or blown up like a balloon.
Once it cools down completely, glass becomes a solid.
And it goes see-through.
That's because the light that we can see isn't absorbed or reflected by the tiny particles inside it.
Like wood or metal.
Since its invention, glass has been used and reused many times over.
You can recycle it forever.
We all use glass.
Every day.
To carry liquids.
To make our homes warmer and brighter.
With windows.
And to keep us connected to our friends and family.
With phones and computers.
Glass can help us see, and not just with our own eyes.
I wear glasses.
Me too.
It's also taken us to distant galaxies.
With telescopes.
And magnified the microscopic.
So you can see really small things.
Where glass will take us next, we can only imagine.
