Explosions: How We Shook the World Page #3

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I'm going to adjust this. Could you give me an update?

- It's at 21 at the moment.

- Right.

- I don't want to scare anybody.

- No, it's OK. What we'll do,

we'll just cool it down a bit. OK.

So what temperature are we now?

- It's down to 19.

- OK, well, we need to get it a bit cooler.

- We're down to 18.4.

- OK.

What's the danger if the temperature starts rising?

We want to keep control of this reaction.

I'm very conscious of this.

- That's OK.

- I know battery acid's quite horrifically dangerous and if that's just as dangerous.

It's much... These are very concentrated acids,

so we've got to be extremely careful.

'The nitration reaction changes the cotton chemically so that now,

'just like in the gunpowder mix, there are carbon, nitrogen

'and oxygen atoms, an explosive reaction waiting to happen,

'but in this substance they're actually all in the same molecule,

'so much closer together than in gunpowder.

'Schonbein had accidentally created a much more efficient explosive.'

So this is it, our nitrocellulose, or guncotton as it's known.

- That's right.

- I mean, now we've washed the acid off and dried it,

it feels exactly like cotton wool.

Just like we started with.

The only difference with this one, compared to the cotton wool,

is that we've got the oxygen actually linked to the fuel.

So because we've changed every single molecule

of the cotton to guncotton,

- then it's going to go exactly the same every time?

- Yes.

- Go on, then.

- Right. Are you ready?

I'm more than a little intrigued.

Stand back.

- I am already.

- Ready?

That gives off a lot of heat.

Heat, light, lots of gas being given out and then you can just have

a look, and there's sort of black bits there, that's the carbon.

So it hasn't fully oxidised.

So there's not enough oxygen for all the carbon that's in the molecules,

- so we're just left with some carbon.

- That's right.

That's a very, very rapid burnout. Whoof.

Like with the gunpowder when you just set it on fire,

it's unconfined, so you don't get an explosion,

you just get this rapid burning.

It all goes up into the atmosphere and it's all disappeared as gases

and that's what you're left with.

- I like it. Can we do some more?

- You can indeed.

Just like gunpowder, guncotton simply burns when there's room

for the gases it produces to expand into

but it burns faster, and the faster the gases are produced,

the greater the explosive potential.

Schonbein recognised it and immediately started

sending out samples to colleagues and writing about his discovery.

One of the first to react to the news

was the Cornish mining community in the far southwest of England.

The area is rich in resources like tin and granite

and it made it a worldwide centre for mining.

It was a vital and profitable industry for England

and in the mid-19th century,

it relied heavily on gunpowder to break up the rock.

By the 1840s, miners had been using gunpowder in mines like this

for 200 years.

But gunpowder was far from reliable. It was dangerous,

unpredictable and difficult to use.

Mine historian Richard Williams has promised to show me just

how difficult, starting with how they got it deep within the rock.

You're trying to actually push a hole into the rock using what they

called a bore, basically, an iron bar about 3ft long.

- Right.

- And a heavy hammer.

- Can I have a go?

I'd love to have a go.

Keep turning it.

I can see that taking a while.

It would probably take you a good 20 minutes.

I can imagine once you've done your 3ft hole,

you'd want to get the best bang out of it you could.

Oh, yes. The next thing is to charge it, to fill it with gunpowder.

You can imagine if they're working with candles or open lamps and

gunpowder, it's not a great combination.

OK, so once they've got the gunpowder into the hole there,

how do they safely light it?

They used a goose quill.

- Basically the centre of the quill is hollow.

- Yeah.

So you cut off the top, you end up with something like that.

You grind your gunpowder up until its fine enough to go into

- the hollow.

- Yeah.

- Tamp that down.

Make several of those, push one into another and slowly you make a fuse.

And they're all packed with gunpowder, so I can see,

but what was the burn-time on them?

Like, how quick did they go?

They were unpredictable.

If you didn't pack them correctly,

they would go off a bit like a rocket.

- That's horrendous.

- Well, when we're doing it,

we're actually going to use a safety fuse and we've already made a charge up

and we've filled this with gunpowder and we've already got

- a hole drilled. The hole is going back into the rock.

- OK.

So we put the powder into the hole.

They would then get a tamping rod to push it in.

- Next thing is to stem it, to seal it.

- Right.

If we left it like that, it would shoot just like a gun.

Visually, this looks quite a short fuse to me.

How much time have we got from when we light it?

This is going to take slightly over a minute and a half

to burn through to the gunpowder.

That seems quite quick, but I'll trust you. I'm going to wear my goggles, though.

Away it goes.

- Here we go.

- Look at that.

I say look at that -

should we not be moving in that direction quite quickly?

- I think we should leave now, yes.

- Yeah.

- So we can just literally just pop round the corner here?

Round the corner so we'll be out of the way of anything that flies down through the tunnel.

You start to wonder if it's going to go.

But it went!

The reverberation afterwards as well, which I guess is

the multiple shock wave bouncing off all sorts of walls.

Well, there we go, you look down the level and we should see the smoke.

Right, you can actually see the fumes are close to the roof looking down through.

- Oh, yeah.

- It's getting thicker as we get close to the...

- It's getting a bit acrid.

- Yeah.

'The smoke was one of the things that miners hated about gunpowder.

'It filled the tunnels and made working difficult.'

What's actually happened is it's blown the studding out.

- We haven't moved any rock at all, have we?

- No.

'So not only was gunpowder difficult and time-consuming for miners to use, it wasn't even that reliable.

'Schonbein's new guncotton promised more power, more reliability and no smoke.'

In August 1846, the Royal Geological Society of Cornwall

invited him to come to England to prove its worth.

Schonbein demonstrated his guncotton in a quarry like this.

The quarrymen drilled several holes in the rock, and into one, they packed a full charge of gunpowder

and into another, just a quarter of the amount of guncotton.

So innocent did the guncotton look that one man said he would sit

on the hole in return for a drink at the local pub.

Luckily, he was persuaded to watch the test

before committing himself to the bargain.

First, 30g of gunpowder.

Let's see if it's more successful than in the mine.

Well, the rock split, but not at the hole where the explosives were.

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