WEBVTT
Kind: captions
Language: en

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[dramatic music]

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- There is one kilo of Semtex
plastic explosive back there.

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This ought to look good.

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[brief, muted explosion]

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Okay. That didn't look great on camera.

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Neither did I.

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The film industry has a lot of tricks
to make the explosions in movies

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look like the audience expects them to,

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all fire and flame and devastation.

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So now, we've seen what an
actual explosion looks like.

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Let's see how Hollywood does it.

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There are two parts to the trick,

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and the first is what
you're actually blowing up.

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- We've just blown up
one kilo of Semtex 1A,

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which is a PETN based plastic explosive.

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Now that's real military explosive.

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So for a Hollywood effect,

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we don't actually use the Semtex
because it does a lot of damage.

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It's designed to do damage
for its military purpose.

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We don't want that.
We want something that looks nice

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but does the minimum
amount of damage possible.

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So what we're going to use
is some detonating cord

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to burst a bag full of petrol,

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and that will be ignited as it goes out

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by an ignition charge off to one side.

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And we're going to do this in
three pots called mortar pots.

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And that will direct the
fuel as it flies out.

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And then it gets ignited,

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and that produces a
nice, big explosive effect.

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There are loads of flames
and fire and dirty smoke.

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We do that to just pointing
towards the camera.

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We don't want to bother
sending it backwards

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or to the sides, particularly.

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We only want it where it's going
to do the effect that we want.

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For the three pots full of fuel,
we're probably going to use

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less than 10 grams in each of them.

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The reason we're getting a bigger effect
using less explosive

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is because of the fuel.

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We're putting that in there
because that will catch fire.

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Big, big yellow flames,
lots of dirty black smoke,

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because it's a mixture of
kerosene, petrol, diesel,

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and any other muck I happen
to have lying around(!)

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Those were in plastic bags in
front of the explosive charge.

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The explosive charge is just
there to propel the fuel out,

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vaporise it, make a big cloud of it,
which can then be ignited.

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So the visual effect is from
the cloud of fuel igniting.

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And the explosive is just
used to create that cloud.

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This is detonating cord.

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It's a thin plastic tube with
some fibre winding inside it,

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but, down the very
centre, it's powdered PETN

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pentaethyle tetranitramine,
a high explosive.

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And when this stuff goes off,
it will detonate along its length.

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That's about six kilometres a second.
So it's pretty powerful.

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But, what we're going to do for
the Hollywood effect, is to reel it up,

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and make like little flat pads of it.

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When that detonates, the blast from it

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will fracture the plastic bag
and spread the fuel out

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and create our cloud of vapour
that we want to ignite.

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The important thing to remember
is when you're using things

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like detonators, or the high
explosives in a mortar pot,

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you need to separate it
from the actual steel pot.

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Because the shock waves from
the high explosive going off

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can actually travel into the steel

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and actually peel bits of it off
and create fragmentation.

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So you need to put a lump of foam
between the explosive and the mortar pot

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to make sure that it doesn't break up and
damage the actors you might have close by.

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- With all the explosives in place,
the second trick is how you film it.

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By moving the camera back and zooming in,

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you make it look like your actor is
much, much closer to the explosion

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and it means the whole frame is filled up

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while everyone's still at a safe distance.

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Then, you shoot in slow motion.

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You make the explosion seem even longer

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by shooting from multiple angles
and repeating it several times,

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and use all the cinematic lens
and colour tricks you can

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to make it look...
well, more cinematic.

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And you tell your actor not to flinch.

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[long, repeated, slow explosive blasts]

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Also, you hope he doesn't
give a cheesy grin to camera.

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Like, we had one take, and
what I did was...

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I should've done sort-of
cold steel glare down the camera.

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I just had a grin on my face
cause I'm firing a thing!

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Did that work?

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I was looking this way.

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I really wanted to look at the explosion.

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Oh, there is... there is a lot
on fire back there, isn't there.

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Wow.