Ceramics: How They Work How It Works

I'm standing on top of the modern world,

on a structure built from some of the most extraordinary materials that humans have invented.

Everything around me is man-made.

And it's built of this.

Sand and clay.

We've transformed sand into transparent glass.

Malleable clay has metamorphosised into hard earthenware

and brittle porcelain.

From rock and ash, we've unleashed the power of concrete,

the most widely used man-made material in the world.

I can see it's bending. It's bending quite a lot.

These miracle materials are ceramics.

All forged from the stuff of the Earth.

And they have one thing in common - the transforming power of fire.

I'm Mark Miodownik and, as a materials scientist,

I have spent my life trying to unlock the secrets of matter.

Yes! It doesn't break!

This is the story of ceramics.

Of clay, concrete and glass.

The materials we've used to make our 21st-century world.

How we've taken the very stuff of the Earth and transformed it

into the buildings around us and the technology at our fingertips.

This is one of the lightest solids on the planet.

It's aerogel, it's 97% air, it's a glass

and it's one of the most marvellous materials ever created.

NASA use it to collect space dust, but let me show you something else it can do.

It's a fantastic insulator.

The temperature under here's about 1,300 degrees.

Now watch this.

I put a flower on it, no problem at all. Absolutely fine.

I can even put my finger on it. It's barely warm.

Absolutely fantastic.

The secret of aerogel lies in its inner structure.

It's actually full of billions of air holes.

It's a glass foam, and that's why it's such a great insulator,

and why it can absorb impacts.

In the future, it might protect us

against bomb blasts or insulate spacesuits on missions to Mars.

Aerogel is almost 100% air.

But it's the part that isn't that's important.

An almost invisible sponge-like glass foam.

Glass, mainly made from sand, is a special type of ceramic.

But the story of how we learned to work ceramics

begins with an earthenware pot.

Clay was the first substance we learned to transform

into a new material, about 29,000 years ago.

And, for me, that's one of the most important moments in our history.

It's the moment where we learnt to take the stuff of the Earth, clay,

soft and malleable, and, using fire,

transform it into something hard, immutable, a ceramic.

The first pottery figurines were found

in what is now the Czech Republic.

Our ancestors dug clay out of the earth, they shaped it,

and baked it in their fires.

Much later, they made it into pots for storing grain and holding water.

But they had little idea of the chemical processes they'd mastered.

Magnified over 1,000 times, clay is made of thin,

crystalline plates which are surrounded by water.

This allows the plates to slip past one another,

which is why the clay can be moulded.

But fire changes it for ever.

As clay is fired, the water evaporates.

So the plates come closer together.

In the intense heat, atomic bonds form between the plates

and lock them into position.

The clay has become hard and brittle.

What later scientists would call a ceramic.

Pottery became one of the foundations of civilisation.

Although it had its weaknesses -

it could be porous and would shatter easily -

it would be thousands of years

before we'd create anything significantly better.

At least here in the West.

It's 1701.

A young alchemist, Johann Friedrich Bottger,

is thrown into a castle dungeon by the King.

Augustus The Strong imprisoned Bottger, not to improve pottery,

but to make gold.

This was an era in which alchemists believed

they COULD turn base metals into gold, a tempting prospect

for any king who wanted to fund their war or their court.

Augustus ordered that Bottger be kept in prison

until he revealed the secret of turning lead into gold.

Picture the scene down in the dungeon.

Bottger toiling in the unrelenting heat and foul air.

Mixing, bubbling and heating endless cocktails of ingredients.

At the end of it all, he produced no gold.

Desperate to keep his head on his shoulders,

Bottger had to find a way to appease the King.

There was one thing that Augustus valued almost as much as gold.

So Bottger set out on a quest to solve an age-old mystery,

and, in doing so, he would change the Western world.

Bottger had set his sights on the finest ceramic

then known on earth - porcelain.

The Chinese had held

the secret of porcelain making for over 1,000 years.

Finer, lighter, harder, whiter, with a glassy glaze.

Porcelain was superior to any pottery we had created in the West.

And it was highly prized. Known as white gold.

The Chinese guarded their secret closely.

It provided them with a huge trade monopoly.

And despite centuries of experimentation and sending spies

to China, nobody in the West could discover the secret of porcelain.

And this was the task that Bottger set himself to save his skin.

He needed to find out how the Chinese changed

coarse earthenware into fine, strong porcelain.

He started with the same basic ingredients

that make earthenware pottery.

So Bottger had to work out what other secret ingredients

the Chinese were adding.

Master potter Graham Taylor has been making porcelain for over 30 years.

He knew what not to try. People tried to do it for centuries.

They tried all sorts of things to add to clay.

They tried adding talc, powdered glass, or shells, things like that,

all trying to achieve that sort of white translucency,

that vibrancy of porcelain.

So what did Bottger try?

Bottger had the advantage of having discovered a really,

really fine type of china clay that came from Colditz.

He then had to find various new things to add to that clay.

There we go.

So, here we've got china clay, pure, white clay.

And in its powder form, it looks like flour.

'Bottger experimented for years before finding

'two critical ingredients to mix with his clay.'

What he's adding to it as well are china stone.

This is a decomposed volcanic mineral.

And quartz, about 20% quartz, so here we've got, again,

-another unassuming white powder.

-Another white powder!

And here, what we've got is the makings, seemingly, of porcelain.

It doesn't look much, does it?

Of course, what we need to add to make it into a clay is some water.

So I'm just putting an amount of water in there.

And we start to mix that up,

and what you see happening here is we will get the paste.

'But Bottger wasn't there yet.

'If earthenware could be forged in a blazing fire, he realised

'he'd have to improve his technology to make porcelain.'

When they write about Bottger's kilns,

they talk about narrow, horizontal kilns,

so I think this is the sort of shape that they might have been.

'By trial and error, Bottger discovered

'he had to get his kiln to an extremely high temperature.

'At least 1,300 degrees Celsius.'

So, we get this burner going.

'At this temperature, a different chemical process takes place'.

The added secret ingredients, china stone and quartz,

react to form a glassy glue.

This flows into the gaps between the crystalline plates.

The plates begin to dissolve.

Needle-like crystals form, which help lock the plates into shape.

As the porcelain cools, the glassy glue

solidifies around these structures and locks them into place.

This makes porcelain less porous than earthenware,

so it's harder and much stronger.

It had taken more than a decade, but Bottger was finally convinced

he had something that might earn him his freedom.

He decided it was time to prove his skills to the King.

Legend has it that, when the King came to visit the workshop,

Bottger decides to open the kiln, and pull out a teapot,

apparently, from the kiln, while it's still glowing white hot,

and plunge it into a bucket of water, to demonstrate

the quality of the ware, and the sort of reported thing at the time

was that he plunged it into water saying it must survive this test.

Thermal shock, surely, would just shatter it.

That's what I would expect, I really am very sceptical, and I think

it's an elaboration of the story, and building up of the story,

something which it maybe wasn't, but Bottger was quite a showman.

-He really was a showman.

-Have you ever tried a test like this?

No, I haven't.

-Nice and quiet.

-Yes. That really makes a huge difference!

-Got it?

-Yes. Off we go.

-Hold on, hold on.

-OK.

-That's it. Horizontally.

-And onto there.

-Oh, yes!

-Beautiful.

Now then, what we have here is one very hot porcelain bowl,

-that has actually fused so much...

-Did you want me to...?

-Yes.

-Tip that back. Into there. Lovely.

-Yeah.

-That's got it.

And what we're going to do is...

-Drop that into there. And it looks like Bottger might have been right.

-My God! I'm really amazed at that!

I can't believe it! It survived! That's amazing!

That's like no ceramic that I have ever seen,

-I really can't believe that.

-That's me proved wrong.

THEY LAUGH It survives perfectly well.

'Bottger had finally solved the mystery of how to make porcelain.'

And he did so while locked up in a dungeon and in fear of his life.

Most people would go to pieces under that sort of pressure,

but Bottger didn't. Instead, he pulled out of the bag

one of the most wondrous pieces of material science.

King Augustus eventually released Bottger in 1714,

13 years after he was first imprisoned.

Following Bottger's discovery,

China finally lost its age-old monopoly on porcelain.

And the balance of manufacturing wealth and power shifted to the West.

But it took a lot less time for the West to unlock

the secrets of another ceramic.

Glass.

It was the Romans who first mastered the skills to make blown glass.

They heated sand with minerals and created a toffee-like substance

that they could blow, stretch and mould into any shape they wanted.

And, unlike any other solid they could make, it was transparent.

Dr Caroline Jackson has studied the techniques of Roman glassmakers.

-The Romans were the first to use glass for windows.

-Really?

-Yes.

-What happened before then?

-They just had either open windows

or, in ceremonial places, they would use other materials,

but that wouldn't let the light in quite so much.

So people must have got pretty cold before the Romans?

It certainly was. In Britain, it would have been quite draughty.

What was the process like to make this glass?

They essentially cast glass.

They'd already got a casting process for vessels,

so it's just an extension of that.

Like pottery, glass can be made from very simple substances

using only the power of fire.

The sand, which is mainly quartz crystals,

and the minerals or ash, are mixed and heated together.

As the temperature rises to 600 degrees Celsius and beyond,

they begin to melt.

The mixture becomes a molten liquid and, like all liquids,

its molecular structure is chaotic.

As glass cools, its atoms bond with one another.

But it can't form crystals as other ceramics would.

That's because it cools too fast for its atoms

to get into the regimented structure of a crystal.

And this is one of the keys to its transparency.

He's taking the hot glass out of the furnace now,

and he's got a wet ladle, so it doesn't stick to that,

then he pours it on to a very hot surface. Again, so it doesn't stick.

And he's pressing the glass down while it's very hot and molten

to try and get as thin a surface as he can possibly get.

The glass is cooling all the time.

He's pulling out now, with pincers, to try and get the square shape,

and you see these actually on Roman glass examples.

You see the pincer marks in the corners, sometimes.

In making their windows,

what excited the Romans was that they could see through them.

The secret of what makes glass transparent is

hidden deep within its atomic structure.

Now everything, whether it's opaque or transparent,

is made of atoms. Imagine this plate is an atom in an opaque material,

and this tomato is its nucleus.

Well, there's also electrons inside the atom,

and they inhabit things called energy levels,

and they look a bit like this.

Now, when a photon of light hits the atom,

well, it can promote one of the electrons to a higher energy level,

so it absorbs that photon of light and so the material is opaque.

So what happens when material is transparent?

Well, you've still got the atom and you've still got the nucleus,

and you've still got the electrons and their energy levels,

but this time, the gap between the energy levels is bigger,

so when the photon of light hits the atom,

it doesn't have enough energy to promote one of the electrons

to a higher energy state, and so, well, nothing can happen, the light

has to travel straight through, and so the material is transparent.

The Romans were justly proud of their glassmaking technology.

They could make more advanced shapes than anybody else.

But there was one other material they invented,

which would have a much greater impact

on both the ancient and modern worlds.

Their inspiration may have come from volcanoes

like Mount Vesuvius and Etna.

When they erupt, they spew out ash and the Romans noticed that,

when the ash got wet, it hardened and became almost as hard as stone.

The Romans saw the potential to make a powerful new material.

A material we now call concrete.

Now I have to admit, although most people loathe concrete,

I think it's one of those amazing materials we've ever created.

I love the look of it, the feel of it,

and the way that it's changed the way we live our lives.

'Chris Brandon has studied Roman concrete for over 20 years.

'And he's going to help me make some.

'We're using volcanic ash called pozzolana ash

'and adding burnt limestone made into a putty.

'The same ingredients the Romans would have used.'

How do we know that Romans made concrete this way?

Is it written down somewhere, a recipe?

Yes, there is a recipe in Vitruvius, Pliny also wrote about it.

'We're not heating our mixture, but heat is still fundamental'.

The pozzolana ash was formed as minerals reacted

in the extreme heat of a volcano.

And the Romans heated limestone themselves.

As the heat drove off carbon dioxide,

it turns limestone into the very reactive burnt limestone -

quicklime.

'We're adding water right now to make the cement paste.

'That's the key ingredient of concrete.'

We must make sure it is a stiff mix.

You can see this is a paste now,

something I can mould and shape into whatever I want.

The water kicks off a complex set of chemical reactions.

New compounds are formed.

Some are gels which harden into these fibre-like fibrils,

which can be seen magnified many thousand times.

The fibrils grow into a hard, interlocking mesh

that is the basis of concrete's strength.

It's a reaction that can keep going for years,

and the concrete goes on getting harder and harder.

It was concrete that gave the Romans their great structures.

Their amphitheatres, stadiums and the Dome of the Pantheon.

Built almost 2,000 years ago,

spanning a distance of more than 40 metres, the Pantheon still

has the largest unreinforced concrete dome in the world.

'Concrete was to create not just the foundations of Rome,

'but of an entire empire.

'The Romans needed to take command of the seas.'

OK, well here's the mini harbour that we want to build.

'And to do that, they had to build harbours'.

-Is this going to go in just like this?

-I hope so.

-OK.

-Drop it down.

-Oh, hey! 'They discovered

'a truly extraordinary property of their concrete -

'it could set even under water'.

-Won't that all just dissolve?

-Let's wait for the water to clear.

-OK.

What we should see is a lump of concrete and water.

I'm amazed. I thought it was going to sort of dissolve into this mud.

And then that will be it. But there it is.

And tomorrow, they'll be solid.

The Romans were very lucky with their raw materials.

The pozzolana ash from the nearby volcanoes

had the perfect ingredients.

When they were mixed together with water and burnt limestone,

they produced compounds that weren't soluble,

so, as soon as the chemical reactions started to form

concrete's incredibly hard mesh, it wouldn't dissolve in water.

-So, Chris, is this how the Romans built their harbours?

-Yes.

They could build out into the sea, where it would have been

impossible to have constructed ports with any other material.

It allowed the Romans to dominate the Mediterranean.

-So this is the stuff of their empire?

-Absolutely.

This is the foundation of empire.

You'd think, with the advances the Romans made in glass

and concrete technology, that the scene was set for the modern era.

But it didn't happen that way.

With the decline of the Roman Empire, the production of glass

fell away dramatically and concrete almost disappeared altogether.

And it wouldn't be for another thousand years

before those two materials were used together again.

For glass, the next great breakthrough

didn't come until the 15th century in Venice.

And it was so significant that the Venetian glassmakers

weren't allowed to leave the city or share the secrets of their art.

To do so, was punishable by death.

Their innovation was this - cristallo glass.

The clearest glass the world had ever seen.

It came from a combination of great expertise

and the perfect raw materials.

The Venetian glassmakers replaced ordinary sand

with these clear quartz pebbles taken from the local river.

They heated them up and submerged them in water to purify them

and then ground them into a fine powder.

The finest sand to create the finest, clearest glass.

At first, this clear glass was just used to make decorative luxuries.

But then, as in so many times in history,

we took a material prized for its beauty

and harnessed it to drive progress.

Colourless glass was about to completely change the way we saw the world.

Glass bends light, so if you can shape a piece of glass so that it

all bends light to a focal point, well, that's what makes a lens.

The light slows down as it travels from air into denser glass,

and this makes light bend.

As the light emerges, it speeds up and bends again.

The amount it bends depends on the shape and thickness of the lens.

Once you can bend light like this, you can magnify.

The perfectly transparent cristallo glass

led the way to an extraordinary innovation.

The telescope.

It was the 17th century and the planets had only ever been seen

as pinpricks of light in the night sky.

But using a telescope he built himself, the renowned physicist,

Galileo, revealed the wonders of these distant worlds.

In Galileo's day, one way to grind class into a lens was to blow it

and open it out into a sheet.

When this cooled, you had to cut a small piece

and then hold it against a spinning cannonball to curve it.

Galileo kept improving his lenses

until he managed to make a magnification of 20 times.

He saw and sketched the mountains and craters on our moon.

And he discovered moons orbiting Jupiter, revealing that

not every thing in the heavens revolved around the Earth.

Our belief in a universe with Earth at its centre

had come crashing down.

Our worldview had been transformed by the glass lens.

A simple disc of heated sand.

But what's even more exciting to me is what happened when

we turned the telescope around and started looking down instead of up.

The irascible but brilliant English scientist, Robert Hooke, wanted to

use the magnifying power of lenses to see what was under his very nose.

He spent much of his life looking down the microscope.

He described a whole new microscopic world

and produced a book of astoundingly intricate drawings.

Using glass lenses,

Hooke had begun to unlock the secrets of life itself.

He had discovered the complexity of inner space.

At last, we would be able to penetrate

further into the hidden world of materials.

We had come a long way with the sand,

clay and rock beneath our feet.

But we were relying on materials which still had weaknesses.

TRAIN WHISTLE BLOWS

To build the modern world,

we'd have to learn to work around their limitations.

For the Victorian engineers, one challenge was concrete.

It had so many advantages. But one fatal flaw.

Dr Phil Purnell has been studying concrete for over 15 years.

Well, today, Mark,

we're going to get you to walk a concrete plank to give us

some indication of how concrete could let us down if not careful.

-Wow, it really is a concrete plank.

-It certainly is, yes.

-We're going to get you to walk across it.

-OK.

So if you would like to sort of get onto that there.

I'm slightly nervous about this, because I can't

imagine that there is a good reason for me walking a plank.

As you gently inch your weight across the plank,

you're making it bend, you're bending the concrete.

And when you bend something, the top of that goes into crushing,

it's being crushed, it goes into compression.

The bottom of it is pulled apart and goes into what we call tension.

'As the plank curves a tiny bit under my weight,

'the top surface becomes concave and is squashed,

'while the bottom is stretched.'

Of course, as I get closer to the middle,

I'm making the plank work much harder.

When you're in the middle, you have

a maximum crushing on the top and a maximum pulling underneath.

-Concrete is very, very good...

-CRASH!

..but as you can see, very, very poor in tension.

-So what we've demonstrated...

-That's exactly what you don't want a building to do!

-Exactly.

-You really don't want that to happen.

-OK, wow.

This is actually a thick piece of concrete, I'm really surprised.

That's as thick as your concrete floors at home or an office block.

-The genuine thickness of concrete.

-Wow.

'The reason concrete can snap like this is down to its inner structure.'

Concrete isn't entirely solid. It's riddled with tiny holes.

When it's compressed, the holes close up

and the concrete stays strong.

But when it's under tension, the holes open up.

Stress will concentrate at the edges of the holes.

Here, cracks can start...

..and the stress can be powerful enough to split the concrete.

As the cracks grow, they join up with other cracks

and can rip the concrete path.

So, to build bigger, we would need to find a way

of working around concrete's one great weakness.

So, what is this trick? What's the answer to making concrete stronger,

resisting these bending forces?

Well, back in the 1850s, there was a plasterer from Newcastle,

called Mr Wilkinson, and he was making concrete floor slabs.

And what he noticed is that these slabs have the tendency

to crack in between the joists.

Just like my unfortunate experience with the plank.

Exactly like your unfortunate experience with the plank, yes.

So Wilkinson noticed where the cracks are appearing

in his concrete floor slabs and he had an idea, and a very bright idea.

And he took some barrel hoops,

took some of the flat hoops that go around and hold a barrel together,

and he placed them in the concrete where he noticed the cracks

were appearing, where he knew we had to resist these pulling forces.

-So he invented reinforced concrete?

-He did. Back in 1853. Yes.

-What a dude.

-Absolutely! He laid the foundations for modern urban life.

Without reinforced concrete, nothing we see around us would exist.

Reinforced concrete might seem simple,

but it works because steel is the perfect partner for concrete.

They both share a surprising quality.

They expand and contract at the same rate when they get hot or cold.

And unlike concrete, steel is strong when it's under tension.

It bends without breaking, like concrete does.

As we learned more about materials,

we found it easier to find clever ways to fix problems.

For instance, we didn't try to stop concrete cracking completely,

just to control it.

So, to test this beam, we're pushing down on it repeatedly

with a force of about 2.5 tons, so we are putting it under the sort

of loads that we might expect, for example, a rail or road bridge

to be put under when large vehicles go over the top of it.

I can see it's bending. It's bending quite a lot.

It's bending quite a lot, yes.

I hate to tell you this, but it's cracking.

It's cracking quite considerably.

But look at the difference compared to our plank in the other room.

Here, our cracks are only travelling a certain way up,

because what is happening is, the steel is holding the beam together,

the steel is holding that crack together.

If I just traced this crack out, to highlight it a bit more clearly.

We can see the crack is travelling up from the bottom of the beam.

But it stops roughly halfway up the beam,

so I will just raw a dotted line there to show where it stopped.

And everything above that dotted line is

going into the crushing force, into compression.

Everything below that dotted line is being pulled, going into tension.

So above the line, the concrete is doing the work.

Below the line, the steel is doing the work.

So we're getting the very best out of both materials.

-So that crack is stable? Nothing to worry about?

-It's perfectly stable.

All reinforced concrete buildings are cracked to some degree,

and the important thing, when designing reinforced concrete,

is to make sure that you have lots and lots

and lots of small cracks instead of one very, very big crack.

Most people see concrete as drab, grey and ugly.

It hasn't got many fans.

But I think it's an extraordinary material.

You can build man-made mountains with it.

Buildings of any shape you want.

Structures that will last for thousands of years.

And that's the secret of concrete's success.

Many of the iconic structures of our era, the Sydney Opera House,

the Millau Viaduct, the tallest bridge in the world,

and Dubai's Burj Khalifa, the world's tallest building,

wouldn't exist without reinforced concrete.

Reinforced concrete is flexible and versatile and it's freed us

from the limitations of stone and brick.

In the age of concrete, the only limitation is our imagination.

The Industrial Revolution didn't just give us reinforced concrete,

manufacturers finally managed to produce clear glass on a mass scale.

So while concrete was giving us bigger buildings,

glass was giving us this - lager.

People started to drink beer out of clear glasses

rather than opaque mugs.

And they didn't like the dark, murky liquid they saw.

So a Czech brewery hired one Josef Groll, who created the clear,

golden brew, far more appealing to the 19th-century eye.

Lager was born and became the world's most popular tipple.

But while we could mass-produce small bits of glass like this,

we still hadn't found the way to make glass at a scale

big enough to build our modern cities.

It wasn't that we hadn't tried to make large sheets of glass,

but they'd always had inherent weaknesses.

If you make glass the traditional way, it may look perfect,

but it will always have a few flaws in it.

And you probably can't even see them with the naked eye,

but with a microscope like this, you can.

So I'm just going to explore the inner world of glass here.

And have a look for some...

Yes, there's one, a little bubble.

And there's another one, a little tiny little air bubble, actually.

And if I refocus, to look at the surface, then, I can see scratches.

Quite a lot of them.

'And any imperfections in glass could have a dramatic effect.'

So this is a modern pane of glass.

And it has very few flaws in it. And so it's pretty strong.

It's pretty impressive.

Now, what if I was to put artificially some flaws in there?

How would that affect the strength?

Got just the tool for the job here.

Let's put this back up again, and right, now,

I've introduced a flaw into this piece of glass, a scratch,

very thin scratch, let's see if it affects the strength.

Mmm. Just as I suspected.

It might seem strange that a single scratch could weaken

an entire pane of glass so catastrophically.

But it all comes down to the nature of ceramic materials.

Any defect courses a point in the glass

where the stress will concentrate.

Even a small force can rip the atoms apart

at the point it's most concentrated.

As the atomic bonds break,

the stress is focused on to the next atom, and the next, and the next.

If the crack reaches a critical length, it's unstoppable.

The whole pane of glass will break.

Perfection is a very appealing concept,

but with glass, it's really a necessity.

The bigger the piece of glass,

the more likely it is to have a fatal flaw.

And if we were going to build big with glass,

you need to find a way of making it more perfect.

The breakthrough came in 1952, over a sink full of washing-up.

Glass technician Alistair Pilkington was trying to achieve

the glassmakers Holy Grail - a sheet of perfect, flawless glass.

The story goes that he was washing up the dishes and he noticed

a film of washing-up liquid floated on the surface of the water.

He had a brainwave.

Pilkington's idea was to create sheet glass

by floating it on a bed of molten metal.

It was an ambitious idea, but brilliant.

And heat was once again the transforming power.

Heating the metal until it was molten would keep the glass

hot enough to remain liquid and, like the washing-up liquid

on the water, Pilkington knew that glass and metal wouldn't mix.

The glass would simply float on top of the molten metal,

spreading out in a puddle.

And it would settle into exactly the same thickness all over,

because of gravity.

When it cooled,

this glass should be as close to perfection as we could achieve.

It took seven years and more than £7 million to develop float glass.

But the process was perfected.

And it's still the way we make large sheets of glass today.

But even flawless glass was still brittle

and dangerous if it shattered.

To use glass for our buildings in huge, weight-bearing sheets,

we needed a glass that was stronger and safer.

A glass a bit more like this.

All right, come on then.

Let's do it properly!

'It takes a 50 kilogram weight propelled at speed

'to break this glass.

'It's up to five times stronger than ordinary glass.

'The secret, again, lies in the material itself

'and the transforming power of heat in a process called tempering.'

The glass is heated and expands. But then it's cooled so rapidly,

that the outside surfaces contract faster than the inside.

This sets up forces within the glass.

The middle ends up under tension, being pulled by the outside,

which in turn is under compression, squeezed.

'This compression force holds it together strongly,

'so it won't break as easily.

'But like an explosive charge waiting to go off,

'once the internal stresses are released,

'the whole pain disintegrates almost instantaneously.

'And it forms, not a few large cracks,

'but millions of smaller ones.'

Instead of breaking into spiky shards

that can cut or even kill you,

this type of glass crumbles into blunt pieces

that won't do you much harm at all.

'But it's still breaks.

'The search was on for a way of making even tougher glass.

'And once again, we turned to a combination of two materials

'with complementary properties.'

This piece of advanced safety glass is actually two layers

of tempered glass, a kind of glass sandwich with a plastic filling.

'Plastic is flexible,

'so it helps the glass absorb energy from impacts without breaking.'

It was so tough,

we can be more ambitious with glass than ever before.

In theory, I should be able to jump on this.

Yes! It doesn't break!

You don't have to use it for windows, you can use it

for floors, for walls, staircases, it will even withstand hurricanes.

Incredible stuff. We can even make it bullet-proof and bomb-proof.

Unbelievable.

Toughened, laminated glass and reinforced concrete

finally brought us into the age of the skyscraper and beyond.

Ceramics are now shaping society in ways that are more profound

than the buildings we live in.

We've discovered that, at the very small-scale,

and at extreme temperatures,

these materials behave in ways that we just hadn't imagined.

And that's propelled us into the information age.

'It's a story that didn't begin in a high-tech lab,

'but in the dentist's chair.' At the beginning of the 20th century,

inventors realised that bent quartz rods could carry light.

And so they created the dental illuminator.

'Then, a German medical student took the idea further.

'He assembles lots of thin fibres into bundles

'to see if he could transmit not just light, but an image.'

His goal was to look at the inaccessible parts of the body during surgery.

'And fibre-optic bundles were perfect.

'They could follow the contours of the body,

'because of a surprising property of glass.'

Glass of the everyday scale is brittle and stiff,

but at the microscale, it behaves totally differently.

It bends.

You can only see this amazing elastic property of glass

in something as thin as an optical fibre,

the diameter of human hair.

Atoms in glass are connected by bonds,

which behave a little like stiff springs.

This means glass can bend a tiny bit.

The finer the glass thread, the less force it needs to bend.

So the less likely it is to crack.

And in such a fine thread, drawn from molten glass,

there's less chance of a defect, which could make it shatter.

That's not the only thing that's special about this glass.

It's also incredibly pure, so light can travel down it for miles.

But light normally travels in straight lines,

so how does it go around these bends?

'To find out, I'm with Dr Natalie Wheeler,

'who researches optical fibres at the University of Southampton.'

So here we have a length of optical fibre, and as you can see,

it's extremely thin, and also, seeing as it's been coated with

a polymer during the fabrication process, it's also extremely strong.

Inside the coating of this optical fibre is a glass core,

surrounded by a glass cladding layer.

It's these two layers that help the light go around bends.

We can actually demonstrate how this works using this set up here.

-If you would like to just pull out that cork there.

-This one?

-Yeah.

Wow! That's amazing! Look at that!

'This laser light mimics what happens in an optical fibre.''

'When light travels from a dense to a less dense medium,

'like this liquid to air,

'or from the glass core to its cladding layer,

'what happens to the light depends on the angle at which it hits the boundary.

'If the angle is large enough, it won't pass through/

'It'll be reflected back in.'

At the interface between the two materials,

the light is being reflected, and you can see it bouncing along here.

So the interface between them allows the total internal reflection?

-Exactly.

-That's absolutely fantastic.

Using these amazing properties of optical fibres, in 1930,

medical student, Heinrich Lamm, successfully transmitted

the first image of a lightbulb filament using an optical fibre bundle.

Then scientists realised they could have a far more powerful use -

to transmit vast amounts of information at the speed of light.

Optical fibres have become a foundation

of the information revolution.

Without them, we wouldn't have our world of instant phone calls,

e-mails, cable TV or the Internet.

Today, a single strand of optical fibre can transmit

2.5 million times more information than a standard copper cable.

In fact, over the last 50 years,

ceramics have been taking over from metals

in a materials revolution that gave us our high-tech, high speed world.

Ceramics have also been replacing metals

in medicine and in electronics.

But there's one essential of life that surely metals are vital for -

electricity.

Electricity travels down miles and miles of metal wires to reach us.

And because of the way metals conduct,

some of the energy is lost along the way.

If I make a small electric circuit with some copper wire,

a battery and a bulb, the bulb burns

pretty brightly, but now, if I just use a longer wire,

65 metres of it, same bulb, same battery,

it's much duller.

So the wire absorbs quite a lot of the electricity.

So when it comes to crossing countries and continents,

we lose a massive amount of energy.

The UK's electricity network loses more than 7% of the electricity

just getting from the power station to your plug.

But that could change and it's all down to the way

some materials respond to extreme temperatures.

This time, the transformation isn't due to the power of heat,

but of cold.

In 1911, Dutch physicist Heike Kamerlingh Onnes

was testing materials at extremely low temperatures.

He cooled mercury down to the temperature of liquid helium.

Minus 269 degrees Celsius.

That's just four degrees above absolute zero.

Onnes discovered something that nobody had ever seen before.

At these extreme temperatures,

mercury conducts electricity without losing any energy at all.

He called it superconductivity.

In a metal, electricity is conducted when electrons travel through it.

At normal temperatures,

the electrons bump into atoms and lose energy.

It's called electrical resistance.

But at extremely low temperatures, the electrons can pair up and

navigate through the atoms without bumping into them and losing energy.

The metal now has no electrical resistance.

Onnes received a Nobel Prize for his work.

And in the years that followed, scientists discovered

that many other metals become superconductors at temperatures close to absolute zero.

With society depending more and more on electricity,

superconductors seem to have a huge potential.

But the breakthrough was as frustrating as it was exciting.

How could we find a use for something that only worked at such extreme temperatures?

What was needed was a material that would perform like the superconducting metals,

but at a temperature that wasn't down near absolute zero.

And when the breakthrough came, it wasn't the material

that anyone expected to conduct electricity at all.

It wasn't a metal. It was a ceramic.

This is a ceramic called yttrium barium copper oxide,

and not only does it not conduct electricity, it doesn't

really behave very interestingly at all to electricity or magnets.

It seems dead. But cold does many strange things to this material.

If we cool it down

and, admittedly, we have to cool it down quite a lot,

to liquid nitrogen temperatures, that's minus 196 degrees centigrade.

It takes a few minutes for the liquid nitrogen to cool it right down,

and when it does, the ceramic becomes a superconductor.

And it has another trick up its sleeve.

Now when I place a magnet over the ceramic,

something completely different happens.

It seems like the magnet floats on air.

What's happening is it is being levitated by the ceramic.

The ceramic is repelling the magnetic field of the magnet.

It's absolutely extraordinary.

The cold has changed the way the ceramic behaves.

It's showing another material miracle

that's unique to superconductors.

Normally, this ceramic isn't affected at all by a magnet.

But when the ceramic is cooled, and becomes a superconductor,

an external magnetic field makes electrical currents flow within it.

These generate their own magnetic field

which repels the external one.

And so a ceramic can repel a magnet.

This ceramic has now become a superconductor and that means

it can conduct electricity without losing any energy.

It can do that when it's cooled to about minus 196 degrees centigrade.

That may sound extreme, but it's pretty warm compared

to the temperatures you need to make metals superconduct.

Since they discovered this,

scientists have begun to design ceramics at the atomic level.

They've added different elements, atom by atom,

in search of their ultimate aim.

Superconductors that will work at practical temperatures.

Degree by degree, we're approaching our goal.

We currently use this thick copper cable to transmit electricity.

But it can now be replaced by this thin superconducting ceramic cable.

And as long as it's cooled, it will lose no electricity.

In America, ceramic superconductors

have started to be used in the power grid.

China and Korea are planning to use them in cities of the future.

In years to come, they could transport electricity on a massive scale.

Just imagine, solar farms in the desert could be supplying

our homes in Britain with minimal energy being lost on the way.

Ceramics have defined our modern world.

From the unlikely beginnings of sand and clay,

we've created the stuff to build amazing cities full of light.

And created the electronic materials that have sparked

an information revolution.

Metals have moved us out of the Stone Age

and helped us conquer land, sea and air.

Plastics brought us the era of man-made materials

and transformed our lives.

Over the last century,

we've designed more new materials than at any stage in human history.

And, as for the future, well, I believe we've only scratched

the surface of what these marvellous materials can do.

Subtitles by Red Bee Media Ltd