Things that go BOOM

[Stephen Alexander Griebel]

After searching "dynamite" in these forums and coming up with nothing but Napoleon Dynamite posts (eeghhh) and searching Mandy for a pyro expert in the southeast and getting nothing, I decided to ask it here.

 

I need to blow up a 10'X17' wall out of cinder blocks mortered together. Obviously, for the safety aspect, I want someone knowledgeable with explosives. It also seems like he would be the one to get dynamite/powder/etc-- I can only imagine that post-9/11 it's even more difficult to get your hands on that kind of stuff. All the pyrotecnic guys on mandy seem to specialize in fireworks and list nothing on explosives experts. I do live near Quantico/Mclean and AP Hill, a big military base in Virginia and would try them as a last resort, just wanted to check with yall first.

 

Oh yeh, any idea how much we're talking for all this?

 

Thanks guys

[Alessandro Machi]

I don't know what it would cost to blow up something that large but don't discount the idea of using minatures instead.

[Michael Nash]

I can't believe I have to say this, but I guess I do: it would be extremely foolish, dangerous, and probably illegal to attempt to actually blow something up with real explosives, especially on your own.

 

I'm not an effects expert, but from the shoots I've been on with effects here is what I've observed:

 

Movie explosions are never the real thing. The object being "blown up" is usually gutted and scored to break away easily, if not a faked or constructed prop altogteher. The visible "explosion" is often a combination of effects like debris blasted from air cannons and gasoline that's "flashed" for the fireball. This allows the "look" of the explosion to be controlled and repeated.

 

The real thing is just way, way, way too dangerous. And even when it is controlled by experts things can still go wrong. I was on a shoot where we "blew up" a car with gasoline flashes. Several minutes after the explosion while the car was still burning, the fire heated up one of the hatchback shocks and it exploded for real. A piece of shrapnel wizzed inches past my nose (100 ft from the car) and struck someone next to me in the neck. They ended up okay, but the size and velocity of the shrapnel could have easily taken an eye out.

 

Just a few weeks ago I had to shoot an effects plate of firecrackers going off for a fireworks PSA. Because this PSA was sanctioned by the Sheriff's Dept., we had to go through the proper safe and legal procedures just for firecreackers -- which meant going out to a remote facility with the bomb squad!

 

 

I knew I guy in Atlanta named Bob Shelly who used to do FX for movies. It's been years so I don't know what he's up to now.

[David Mullen ASC]

If you hire or chat with a licenced efx person that does explosives work, they would at least know the procedures for real demolition work, who to contact, what permits are needed, etc. Or conversely talk to a professional demolition company.

 

I'm sure it's more expensive to blow-up something really solid than to blow-up something faked for movie work, just due to the volume and type of explosives needed.

 

Obviously there is a major safety concern for shooting the explosion.

[Stephen Alexander Griebel]

Thanks guys, I decided to go with a wrecking ball instead.

[Brad Grimmett]

We blew all kinds of things up on a movie I did last year (boat, car, double-wide), and they used napoline for most of it. It looks a lot bigger than it really is. I can't imagine actually using dynamite.

[Hal Smith]

Real explosions are visually messy, there was a PBS "Nova" this year that covered explosive's history. They had a lot of tape of the real thing. All of the explosions that had enough Chutzpah to really destroy things were visually very un-cinematic. They looked like a giant ball of flame and smoke followed by c**p flying randomly all over the place. Just like everything else in film, what looks good is a very designed "good look".

[Kevin Zanit]

As was said before, pyro for movies is more about creating the illusion of power, not actually using it as it would be for demolition.

 

It would be extremely rare to actually use TNT on anything movie related. It is an extremely high explosive more suited to shattering rock.

 

Naphthalene powder mixed with black powder (called a salt & pepper mix) with a small black powder lift charge in a mortar is one method of creating a very fast fire ball that is fairly clean in the sense that it does not send burning gasoline onto the floor (as a gas fireball would).

 

For your particular application, if you are actually trying to blow a 10'x17' wall for demolition purposes, why? You just knock something as weak as a wall over. If one was going to blast a wall like that, you would drill holes into the wall, favoring the base, and put your explosive into the holes. Be very far away from it, as it will send chunks of rock everywhere.

 

You won't be able to get your hands on TNT, nor should you. Messing with high explosives is a good way to die. Try to find some pros to make it safe and legal.

 

 

Kevin Zanit

(I used to work with pyro guys before getting into this side of things, decided I like having all my fingers)

[Bob Hayes]

Although motion picture explosions fake the severity of the blast the explosives and explosions are very real. SFX guys often use the same military explosive we are using in Iraq. TNT is pretty unstable and a crude explosive so is not used often. Despite the care used by good stunt folks the danger from concussion or blast fragments are very real. Do not under estimate their danger.

[Joseph Boyd]

I'f you're on a budget, you could try scoring and precutting the non-visible side of the wall with a concrete saw and a grinder with a diamond blade to create smaller fragements. A modified hydralic log splitter seems like it would do the trick to take it out. Don't know how well it would work, but I do think that scoring the concrete with a grinder may produce a better fragmenting effect with the wrecking ball.

[Kevin Zanit]

Well, commercial TNT is actually extremely stable, but is rarely used in SFX, and may start being slowly fazed out even in blasting because of newer technology, such as PETN (which is one of the most powerful high explosives, but is less stable than TNT).

 

Some explosives used in the military are used in demolition, but not much in film, except for Primacord perhaps (which is mostly made of PETN). You won't find C4 on a film set, but if you do, call me, I want to watch ;)

 

Most SFX work can be accomplished with low explosive like black powder, compressed air and some ingenuity.

 

 

 

Kevin Zanit

[Bob Hayes]

Well, commercial TNT is actually extremely stable, but is rarely used in SFX

 

I stand corrected. Prima cord seems to be the most common high explosive I am around.

[Kevin Zanit]

Primacord (aka det. cord) can be fun stuff. I remember a demo I saw of it where they wrapped some around a giant tree trunk, set it off, and the tree fell strait down, with a super clean cut, it was like a laser.

 

 

Kevin Zanit

[dd3stp233]

Safety issues aside, you can buy 1/2 sticks of dynamite over the counter in Mexico, in fireworks shops. I wouldn't recommend trying to bring them back across the border, though.

[Michael Collier]

Real explosions are visually messy, there was a PBS "Nova" this year that covered explosive's history. They had a lot of tape of the real thing. All of the explosions that had enough Chutzpah to really destroy things were visually very un-cinematic. They looked like a giant ball of flame and smoke followed by c**p flying randomly all over the place. Just like everything else in film, what looks good is a very designed "good look".

 

I don't know about all that. Did you see that mythbusters where they put several boxes of TNT into a concrete mixing truck(with about 4feet of dried concrete on all sides of the drum)? If they had shot that on film, it would have been the most cinematic explosion ever. It seriously released a shockwave that was visible from the dust it kicked up like in Sum of All Fears.

[Hal Smith]

I don't know about all that. Did you see that mythbusters where they put several boxes of TNT into a concrete mixing truck(with about 4feet of dried concrete on all sides of the drum)? If they had shot that on film, it would have been the most cinematic explosion ever. It seriously released a shockwave that was visible from the dust it kicked up like in Sum of All Fears.

Yah - that shot does look great, there's a bit of it on their website. I don't know if they had a consultant but using concrete inside a steel housing as the containment for 850 pounds of high explosive is almost a textbook example of how to build a "big bang". :)

[Kevin Zanit]

I think it was the FBI who helped them with that. I don't remember if it was TNT, but it was a pretty cool explosion.

 

I have a friend who was in EOD in the military and he had some cool videos of blowing up giant arms caches with shockwaves that go for thousands of feet. Try searching on a site like youtube, there are tons online.

 

 

Kevin Zanit

[Hal Smith]

I think it was the FBI who helped them with that. I don't remember if it was TNT, but it was a pretty cool explosion.

Yes, they had a retired FBI explosives expert advising them - I'm not certain that they ever said exactly what they used - more Homeland Security nonsense. Like Al Qaeda doesn't already know all they need to know about explosives.

 

My most notable "Homeland Security" experience this year was walking into the local grocery store where, out in their entrance area, they had a sale going on. They had nail polish remover (acetone) on sale right alongside hydrogen peroxide, also on sale. Instant TATP and one stop shopping to boot. TATP? That's what the London tube bomber a**holes used.

 

That demolition firm that implodes buildings put on a pretty good show blowing up a bunch of Warsaw pact tanks, scud launchers, etc. The NATO brass was in attendence so they designed all sorts of cool BOOMS!

[Riku Naskali]

I've seen dynamite and other mining explosives used on a set. They used it to blow up trees and fake mortar hits far away in the ground for a war movie. Obviously it's powerful stuff and can't be used anywhere near people.

[Bob Hayes]

The largest explosion I?ve ever filmed was 80 sticks of dynamite and 350 gallons of gasoline in a DC3. That was big. The most interesting part how ever was the plane had a lot of magnesium components and after the explosion sections would ignite and burn like wielding torches.

[Stephen Alexander Griebel]

If one was going to blast a wall like that, you would drill holes into the wall, favoring the base, and put your explosive into the holes. Be very far away from it, as it will send chunks of rock everywhere.

That's what I was going to do actually. I am of course in search of an expert-- never really planned to gun it alone, but like I said above, I'm going to use a wrecking ball anyway-- fits the particular scene better.

 

Thanks for all the replies, guys!

[Bob Hayes]

A film company would never blast a cinder block wall for a film. The amount of explosive would be enormous and the shrapnel would be so lethal the crew and equipment would have to be prohibitively far away. Quite often film crews will use Fiberboard (cellulosic fiber) which is the lightweight material used for drop down sealings. When subjected to an explosion it looks and behaves like heavier material but it is much less lethal. The art department would cut and shape it into a cinderblock wall. A high explosive would still be used sometimes in conjunction with an air cannon. Even in the most controlled situations this is very dangerous and small apparently innocuous things like nails can become deadly.