There is one kilo of Semtex plastic explosive back there.

This ought to look good.

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, vaporize 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 fiber winding inside it, but, down the very center, it's powdered PETN, Pentaerythritol Tetranitrate, a high explosive.

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

That's about six kilometers 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 vapor 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 color tricks you can to make it look... well, more cinematic.

And you tell your actor not to flinch.

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

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

I should—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.