[dramatic music] - There is one kilo of Semtex
plastic explosive back there. This ought to look good. [brief, muted explosion] Okay. That didn't look great on camera. Neither did I. The film industry has a lot of tricks
to make the explosions in movies look like the audience expects them to, all fire and flame and devastation. So now, we've seen what an
actual explosion looks like. Let's see how Hollywood does it. There are two parts to the trick, and the first is what
you're actually blowing up. - We've just blown up
one kilo of Semtex 1A, which is a PETN based plastic explosive. Now that's real military explosive. So for a Hollywood effect, we don't actually use the Semtex
because it does a lot of damage. It's designed to do damage
for its military purpose. We don't want that.
We want something that looks nice but does the minimum
amount of damage possible. So what we're going to use
is some detonating cord to burst a bag full of petrol, and that will be ignited as it goes out by an ignition charge off to one side. And we're going to do this in
three pots called mortar pots. And that will direct the
fuel as it flies out. And then it gets ignited, and that produces a
nice, big explosive effect. There are loads of flames
and fire and dirty smoke. We do that to just pointing
towards the camera. We don't want to bother
sending it backwards or to the sides, particularly. We only want it where it's going
to do the effect that we want. For the three pots full of fuel,
we're probably going to use less than 10 grams in each of them. The reason we're getting a bigger effect
using less explosive is because of the fuel. We're putting that in there
because that will catch fire. Big, big yellow flames,
lots of dirty black smoke, because it's a mixture of
kerosene, petrol, diesel, and any other muck I happen
to have lying around(!) Those were in plastic bags in
front of the explosive charge. The explosive charge is just
there to propel the fuel out, vaporise it, make a big cloud of it,
which can then be ignited. So the visual effect is from
the cloud of fuel igniting. And the explosive is just
used to create that cloud. This is detonating cord. It's a thin plastic tube with
some fibre winding inside it, but, down the very
centre, it's powdered PETN pentaethyle tetranitramine,
a high explosive. And when this stuff goes off,
it will detonate along its length. That's about six kilometres a second.
So it's pretty powerful. But, what we're going to do for
the Hollywood effect, is to reel it up, and make like little flat pads of it. When that detonates, the blast from it will fracture the plastic bag
and spread the fuel out and create our cloud of vapour
that we want to ignite. The important thing to remember
is when you're using things like detonators, or the high
explosives in a mortar pot, you need to separate it
from the actual steel pot. Because the shock waves from
the high explosive going off can actually travel into the steel and actually peel bits of it off
and create fragmentation. So you need to put a lump of foam
between the explosive and the mortar pot to make sure that it doesn't break up and
damage the actors you might have close by. - With all the explosives in place,
the second trick is how you film it. By moving the camera back and zooming in, you make it look like your actor is
much, much closer to the explosion and it means the whole frame is filled up while everyone's still at a safe distance. Then, you shoot in slow motion. You make the explosion seem even longer by shooting from multiple angles
and repeating it several times, and use all the cinematic lens
and colour tricks you can to make it look...
well, more cinematic. And you tell your actor not to flinch. [long, repeated, slow explosive blasts] Also, you hope he doesn't
give a cheesy grin to camera. Like, we had one take, and
what I did was... I should've done sort-of
cold steel glare down the camera. I just had a grin on my face
cause I'm firing a thing! Did that work? I was looking this way. I really wanted to look at the explosion. Oh, there is... there is a lot
on fire back there, isn't there. Wow.
Some menTom Scott just wants to watch the world burn.Cool guys don't look at explosions, and Tom is certainly no exception
This was a cool video. I feel like most people sort of know this already but they did a great fun video.
The key idea here is brisance. Most military applications for high explosives are to destroy something and brisance is the measure of the shattering effect of an explosive based on the speed it reaches peak pressure.
If you want to cut a steel cable or destroy a radio tower, you don't want a big heavy explosive that may move it, you want a small powerful explosive that will shatter the metal before it can deflect.
Stick the same explosives underwater though and you get very cool fountains.
This is a BBC news YouTube chip of 2015 Tianjin explosion.
https://www.youtube.com/watch?v=993wlZ6XFSs
Just felt like hell is coming for you, no movie can compare to that.
Movie and real Look different? Yes
Movie looks more powerful? Hell No
Guy talking like he's at 1.5x speed.
A Great meme template was born this day.
Am I the only one that thought the opening shot was a giant brick of watermelon?
Didn't Mythbusters do this as well in one of their Hollywood Myths shows?