and had the actual explosion force

from C4 going off, you'd have to have a big sign

that says "Put in your earplugs now."

[explosion]

- Remind me not to come to your movie theater.

[laughing]

[fire crackling]

- Jesus Christ!

[dramatic music]

[explosion]

- Hi, I'm Paul Worsey and I'm a professor

of explosives engineering.

- And I'm Tassilo Baur, a special effects supervisor

in Los Angeles.

- Today, we're going to review explosions

in TV and film from a scientific perspective

- And a filmmaking perspective.

- "Desperado." [gunfire]

[upbeat music, gunfire]

- Jack?

[upbeat music]

[explosion]

In the guitar case, we see some modern-era grenades.

But unfortunately, they're rolling around.

And that's not the sort of thing I'd want

to do with grenades is have them rolling around,

bouncing into each other.

Now I personally wouldn't throw a guitar case full

of grenades at my girlfriend.

These look like wire-round grenades

inside those casings rather than a segmenting grenade.

The original grenades were pineapple in design.

And they were supposed to break up into large chunks.

And that was the idea on them.

And these large chunks were propelled out and killed people.

Modern grenades are designed to give a lot of fragments,

very small fragments which are termed frag.

The term shrapnel is usually used accidentally

instead of frag in a lot of films.

And shrapnel actually is ball bearings.

And there was a shell called the shrapnel shell.

And it was invented by Mr. Shrapnel.

So, in a shrapnel shell, the ball bearings are there.

And they're blown everywhere by the explosives.

Frag comes from a steel casing that's broken.

It's turned into pot metal by the detonation wave.

And then these small pieces fly everywhere.

They're sharp, do a lot of damage.

In a lot of movies, somebody will throw a grenade

and you'll see a huge fireball.

And that's not really realistic

unless they set off a propane tank that's just off-frame.

A frag grenade when it goes would be a poof,

a rather large bang,

but you definitely won't see a lot of flame.

- To create that effect,

they would have placed explosives specifically

with a view toward causing that wall of fire.

And the grenades of course are simply props

that the stunt performers on the ground react to.

To create this explosion,

they probably would have used gasoline lifted

by charges placed between the two buildings.

You can even see in the top right corner part

of what seems to be the bag

that the gasoline was likely poured into.

Then there's a smaller explosion

where they're flung away from it,

which is probably done with an air ramp

or something to allow them to jump the way they do.

And then we see the wide shot of the two main actors

against a fireball and it's done very cleverly

in that there's really good protection for them

and of course, it's on a long lens

to compress the distance between them and the fireball.

The fireball is actually between the two buildings.

So it's basically going up like a wall

instead off billowing out like a mushroom.

So other than the radiant heat,

there's really no risk to them.

And they're good actors so they don't flinch.

They carry it off and it makes a great shot.

[upbeat music]

- [Paul] "Batman."

[dramatic music]

[hissing, dramatic music]

[panting, dramatic music]

- Meow.

[explosion]

- In this sequence, we're seeing a lot more complex effects

than just the explosion.

First off, the Catwoman performer punches

through the metal door to the cabinet.

And the metal door to the cabinet,

obviously, would have to be prepared

in such a way that this performer could punch

through it safely and it would look like it was supposed

to when it broke.

This sort of thing is what's called a breakaway.

And frequently it's made so you can replace it quickly.

So you can do multiple takes.

Once she rips it open, we then see her break the gas line

and gas escaping and there's a sign there that says "gas."

But just to show us visually what's happening,

there's a substance streaming out of the broken line.

The time the film was made, that was probably freon,

a component of air conditioning systems.

Unfortunately, that has ozone-destroying properties.

So currently, we would probably use something

like liquid nitrogen or liquid CO2

to create a visible jet of gas.

Then we see her put spray cans into the microwave

and start it, which then appears

to trigger the larger explosion.

- Whether this is realistic or not,

I think it looks really, really good.

And I've seen a lot of gas explosions

and they can look quite spectacular.

This is what happens in people's house sometimes

that the gas escapes and it builds up

in the house and it builds up slowly

to the lower end of the explosive limits.

And then there's a spark of some sort

and that's all it takes.

I would expect personally to see a little bit more

of a blue color to it.

When you do combustion, if you're on the lean side,

it tends to be a little bit blue.

And if you've got too much fuel in there,

it goes on the yellow side.

- To manage the risk in this explosion,

they used very cleverly a series of different ones.

First off, you see the real performers

in the configuration in front of a building,

which probably had no explosives in it

to set up the geography of the shot.

Then you see an over-the-shoulder shot,

with what is very likely a stunt performer

as Catwoman, which is convenient

because she happens to be a wearing a costume

which lends itself toward that.

And that later you see a much wider shot

where there are no performers in the proximity

to the explosion at all,

which they can have a full-force explosion.

So they go from no explosion to smaller explosion

to a huge explosion and by cutting them all together,

it creates the illusion

that the performers are right next to it.

The over-the-shoulder is clearly shot

with a very long lens with a view

toward compressing the distance

between the explosion and the performers.

Very successfully it also makes the shot more dramatic.

The other thing that they will tell stunt people

to do is move a little bit or they'll think you're a dummy.

Humans are looking for human characteristics.

That's why they'll very often have the stunt performer make

some sort of small movement leading

into or reacting to the explosion, even if it's minimal,

just to show you that it's not a dummy.

- In a real explosion, okay, there's gonna be a shockwave.

And that will cause things to move, okay.

I have some footage underground

where we have our explosive camp

for high school students and the campers are there.

And we shoot dynamite about 100 foot down the tunnel.

All that force comes towards them.

And what it'll do is it'll blow their hair all

over the place on the girls and the pant legs

on everybody will flap backwards and forwards.

And sometimes if you use enough,

it'll knock off hardhats if they're in just the right place.

So it's quite an experience.

[explosion]

- [Tassilo] "The Dark Knight."

[explosions]

This was a real building demolition done

for the movie actually on a real building

that was scheduled to be demolished in any case.

- [Christopher] We blow up a lot

of different things in this film.

And with our major explosions,

I was determined to do one of them for real.

- It's very important as special effects people

that we keep current and enhance our skills

to the degree that we can,

but it's also important to know our limits.

Building demolition people shouldn't do special effects.

And special effects people

shouldn't do building demolitions.

It's apples and oranges.

In this case, you have two separate disciplines working

together to create this overall effect.

- We're working in very close conjunction

with Chris and his crew.

So they'll have their special effects going off.

And it won't interrupt our demolition charges.

- On the demolition side, I can tell you exactly

what happened.

The windows start to reverberate and shake.

And that happens roughly five seconds

before the building actually starts to fall.

And those reverberations are made

by detonating cord going off inside the building.

The actual concrete columns inside

that building will each have had say three

or four explosive charges,

which are actually drilled into the concrete.

Then they're wrapped with chain link fence and geotech.

- All of this material is to prevent any debris

from flying out of the building when we blast.

- So that stops all that concrete flying everywhere.

And when you blast that pillar,

what you wanna do is you wanna turn

that concrete into its original ingredients,

which is lime, sand, and aggregate.

And what happens is it gets blown off the rebar.

And the rebar inside the concrete is just like a string.

And it gives the concrete tensile strength

and bending strength but as soon all that concrete has gone,

the actual rebar gets pancaked.

- The debris is handled very effectively

in this particular sequence because we want the talent

to be close enough to the explosions

to tie it together without subjecting them

to a great deal of potential risk.

As you notice, before things get really serious,

the talent is all inside the bus,

which probably has the windows replaced

with something that doesn't break,

some sort of polycarbonate or something.

So they're really well protected in there,

not only from debris, but from sound.

As Dr. Worsey pointed out, all the stuff is contained

by the chain link fence and all these precautions

that are taken.

You don't get that debris flying off.

So what we supply is lightweight debris that's controllable.

It flies off in a visually spectacular way

and enhances the effect.

From looking at some of the behind the scenes images,

you can see that the debris mortars were actually,

as is common, firing pieces of cork and lightweight debris.

And the metal drums were probably filled

with a combination of gasoline

and something else to make it more visually interesting,

which then creates the fireball.

- And with all those explosions going on,

he doesn't lose it for one iota.

Just the perfect performance.

- You can make the actors as safe

as they can possibly be, but if they don't feel safe,