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Q&A: Special F/X Coordinator Dennis Petersen

Special Effects Coordinator Dennis Petersen talks about the importance of staging realistic explosions, staying true to character, and what can happen when a watch meets a car battery.

Q. One scene that you worked on that really stands out is Walt’s confrontation with Tuco. Can you explain your input there?

A. In the scene, Walt throws a piece of fulminated mercury into the ground and that creates the explosion that blows out the windows and stuns Tuco and his henchmen long enough to give Walt the upper hand. The way the scene is shot, we see Walt throw the crystal of fulminated mercury at the ground inside. Then we cut outside for the filming of most of the actual explosion. We had to wrestle with the size of the explosion and how big we could make it. Of course if it’s too big it won’t be plausible that the people inside the building will have survived, but if it’s too small there’s really not much to it dramatically.

Q. How do you film something like that?

A. The art of what we do is in using as little force as possible in
order to create as big an effect as we can. It’s safer and it’s more
fun. It also lets us work more effectively with Vince [Gilligan]. On
the day of the shoot, Vince isn’t the kind of guy that will want to go
bigger with the effects, he just gets more clever. On this particular
day, he came up with the idea of filming the blast from below, with a
camera that would get obstructed by flying debris. If I’d gone bigger
we couldn’t have pulled that off.

Instead of creating one big blast, what we did was create four smaller ones that would happen very quickly and in a very precise order so that we’d achieve the effect of one big explosion. Each one was placed on its own circuit. In the first circuit a squib broke the glass in the windows and it also released the cables that we were using to hold the air conditioners in place. So the air conditioners weren’t blown out of the room, they were really just dropped when the circuit released those cables.

The second circuit consisted of lifters and a pair of mortars set up behind the windows that shot wet sand and about two and a half gallons of tempered glass through the window. This creates the effect of the glass exploding out and it also gets the air conditioners moving a little bit faster. The third circuit fired our debris mortars. They’re set up behind pieces of balsa wood, which we’d angled up against the windows. They also held in place some ceiling tiles, which we like to use because they burn very easily and create a nice smoky effect, but at the same time they’re light and are not going to hurt anyone. Once the third circuit fires, all the debris is catapulted out the window by the blast. The fourth circuit consists of a magnesium flash, it’s a lot like the flash of a camera. Normally we’d have started the process with the flash, but in this case the windows were painted black so we’d never have seen it.

So the blast happens in this four part process, but all the parts happen in such quick succession that they seem to happen nearly instantaneously. What we didn’t know when we were planning it out was that Vince would come up with the idea of shooting the blast from directly below such that the camera would get obliterated by the debris. Since we set the shot up so that it would happen in stages anyway we were able to make the adjustment and pull it off.

Q. Another scene that stands out is Walt’s sabotage of the “KENWINS” car in “Episode 4: Cancer Man.” In the real world, if Walt had bridged the terminals of the battery with a squeegee like that, would the car have blown up?

A. It wouldn’t blow up in quite the way that we depicted it, but it would certainly freeze the battery due to the current flowing through it. And it would spark and melt down; at that point either stuff will start to catch fire or the battery will run out. It’s very destructive. In fact I have a friend who had an unfortunate accident in a somewhat similar situation. He was working with four car batteries, but it was the same voltage and his watch accidentally bridged two of the terminals. The electricity froze him to that spot. He couldn’t break the connection before the watch got VERY hot and he’s got a very nasty scar there on his wrist to this day.

When it comes to creating the explosion we had to really wrestle with that aspect of realism. It was really very important that the level of the explosion be just right and I think we pulled that off. In general we try to hit that balance exactly right and if we have to, we’ll err a little bit on the side of being entertaining. There’s also the character element that was very important to Vince. Vince wants Walt to be a guy who will take revenge on this jerk at the gas station, but he’s not going to create an explosion so big that it’s going to destroy the entire gas station. We needed to keep it true to Walt.

Q. So how do you pull off an explosion like that on film?

Well there’s a two-part process here, although it all happens very quickly on film. In the first part we use a circuit to set off what we call a “shotgun” mortar with wet sand in it. This is what provides the force to lift the hood up. In the second part of the process we use another circuit to set off our “soft pack” which consists of a black powder and rubber cement charge that creates the fireball effect that we wanted to simulate the gas exploding in the car. Of course there’s no real gas in the car when this is happening — for safety reasons we take out the gas and the battery. The battery that you see in the finished episode has been drained of its acid and filled with water instead.

Q. In a case like this, how are you sure that you’ll get the level of explosion that you’re looking for? Do you blow up multiple cars?

You can test it out and the testing saves me a world of trouble when it comes to the actual day of the shoot. What I did in this case was fabricated a rough mode of the BMW we’d be using with a custom-built frame of tubing and steel topped with the hood of a Honda we’d gotten from a junkyard. I set up two video cameras and ran through the blasts exactly the way I wanted to do it on the day of filming. Once I had that videotaped, I was able to bring it to Vince and the rest of the production crew, and everyone was able to sign off on the size of the blast they wanted before we had to do it in a real car on the day of the shoot.

Q. On the day of the shoot how many cars would you destroy to get that shot?

A. Ideally, we like to do three takes and use the best shot that we get from the three takes. In this case we only had one car that we could use. We would have been able to repair the damage by hammering out the hood if we’d needed to shoot it again if we really needed to, but our focus was on getting it right the first time.

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