# How they make movie explosions so fiery? **URL:** \ **Category:** Factual Questions\ **Created:** [February 14, 2015, 12:24am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617 "2015-02-14T00:24:31Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![Qwertol](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Qwertol](https://boards.straightdope.com/u/Qwertol)\ **Post date:** [February 14, 2015, 12:24am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/1 "2015-02-14T00:24:31Z")
How they make explosions in movies so spectacular, with blowing flames and everything??? I mean real explosions are usually not that showy - it’s mostly just an expansion of gas - just like in definition of an explosion. There are no flames unless there was already a fire before… Do they use some special explosives when doing special effects? ---
**Author:** ![boffking](https://avatars.discourse-cdn.com/v4/letter/b/858c86/32.png) [@boffking](https://boards.straightdope.com/u/boffking)\ **Post date:** [February 14, 2015, 12:35am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/2 "2015-02-14T00:35:34Z")
According to Mythbusters, they use gasoline in movie explosions. That is how they make the big fireballs. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [February 14, 2015, 12:38am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/3 "2015-02-14T00:38:43Z")
Lots and lots of gasoline. Plus kerosene for the roiling extra black smoke. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [February 14, 2015, 12:59am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/4 "2015-02-14T00:59:52Z")
In Independence Day (ID4) the pyrotechnicians used propane diluted with CO2, and chunks of cardboard for flying debris. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [February 14, 2015, 1:17am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/5 "2015-02-14T01:17:37Z")
> [@boffking](#): > > According to Mythbusters, they use gasoline in movie explosions. That is how they make the big fireballs. On Mythbusters (remember, they did work in movies for a long time) Adam wrapped two gallons of gas with some det cord and got a huge explosion. This clip shows the [same thing](https://www.youtube.com/watch?v=OEqIiflPpp8). Add in some extra effects to flip the car over or make it more explode-y, some sound on the low end to make it rumble and you’re set. ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [February 14, 2015, 2:57am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/6 "2015-02-14T02:57:22Z")
[Dateline NBC got some really good explosions](https://www.youtube.com/watch?v=KtpMzGN9uWc) with simple pyyrotechnics. > [@](#): > > We acknowledge the placing of the incendiary devices under the truck was a bad idea from start to finish. ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [February 14, 2015, 7:15am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/7 "2015-02-14T07:15:06Z")
I read somewhere long ago that naphtha was was useful for fiery explosions. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [February 14, 2015, 7:49am UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/8 "2015-02-14T07:49:59Z")
It depends on the result you want. If you want a rising fire ball, gasoline. less smoke, lots of hot fire for a short time. If you want fire stuck in place, and makes more black smoke, napalm – a mix of thin and thick gasoline products … which vary from thick oil to tar like. If you want an explosion that creates fireballs , burning stuff… eg wood from a shack exploding, naptha, fire starter blocks… High Explosives don’t make much light … so they have to add hydrocarbon type products to get visible fireballs showing. gasoline doesn’t actually explode with damaging force by merely catching a light. Its possible that if it was mixed into the air and the air then ignited, sufficient air would be heated all at once to blow out windows. ---
**Author:** ![Terminus\_Est](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/terminus_est/32/3087_2.png) [@Terminus\_Est](https://boards.straightdope.com/u/Terminus_Est)\ **Post date:** [February 14, 2015, 12:13pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/9 "2015-02-14T12:13:35Z")
> [@kunilou](#): > > [Dateline NBC got some really good explosions](https://www.youtube.com/watch?v=KtpMzGN9uWc) with simple pyyrotechnics. Also, note that the pyrotechnics were under a large tank of gasoline. ---
**Author:** ![boytyperanma](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@boytyperanma](https://boards.straightdope.com/u/boytyperanma)\ **Post date:** [February 14, 2015, 12:48pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/10 "2015-02-14T12:48:39Z")
These days it’s less gasoline and more CGI. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [February 14, 2015, 1:07pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/11 "2015-02-14T13:07:29Z")
> [@boytyperanma](#): > > These days it’s less gasoline and more CGI. I’m not a movie technician. But I thought that they would still use footage of a real gasoline explosion and then CGI it into the movie. Putting aside realism, it would seem cheaper to blow up a few gallons of gas rather than try to create the same image out of nothing with computers. ---
**Author:** ![sidecar\_jon](https://avatars.discourse-cdn.com/v4/letter/s/a5b964/32.png) [@sidecar\_jon](https://boards.straightdope.com/u/sidecar_jon)\ **Post date:** [February 14, 2015, 1:11pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/12 "2015-02-14T13:11:05Z")
A friend about 10 years ago blew up cars for TV and film, he used gas cylinders with leak valves called “pigs”. A closed car was measured for volume the correct optimum mix gas to air calculated over time and an igniter was wired to make it all go boom…instant fireball. ---
**Author:** ![TwoCarrotSnowman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/twocarrotsnowman/32/15879_2.png) [@TwoCarrotSnowman](https://boards.straightdope.com/u/TwoCarrotSnowman)\ **Post date:** [February 14, 2015, 1:18pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/13 "2015-02-14T13:18:49Z")
> [@Little\_Nemo](#): > > I’m not a movie technician. But I thought that they would still use footage of a real gasoline explosion and then CGI it into the movie. Putting aside realism, it would seem cheaper to blow up a few gallons of gas rather than try to create the same image out of nothing with computers. And _much_ more fun. 🙂 ---
**Author:** ![bashere](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@bashere](https://boards.straightdope.com/u/bashere)\ **Post date:** [February 14, 2015, 2:33pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/14 "2015-02-14T14:33:32Z")
> [@Little\_Nemo](#): > > I’m not a movie technician. But I thought that they would still use footage of a real gasoline explosion and then CGI it into the movie. Putting aside realism, it would seem cheaper to blow up a few gallons of gas rather than try to create the same image out of nothing with computers. My cite for this is sadly weak (it is “I know quite a few people with the flame effects certifications”), but it is a lot cheaper, and, even with all the appropriate safety training in place, not that hard or expensive. My bet would be that it is a lot easier to CGI a real explosion into a film than to try to create one. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 14, 2015, 4:29pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/15 "2015-02-14T16:29:18Z")
> [@Little\_Nemo](#): > > I’m not a movie technician. But I thought that they would still use footage of a real gasoline explosion and then CGI it into the movie. We have the physics of this sort of thing down quite well now, with [off-the-shelf particle](http://en.wikipedia.org/wiki/Particle_system) and [other modellers](http://en.wikipedia.org/wiki/Fluid_simulation), so explosions are easier than ever before. > [@](#): > > Putting aside realism, it would seem cheaper to blow up a few gallons of gas rather than try to create the same image out of nothing with computers. It seems cheaper to pay for gas rather than electricity? I mean, they don’t buy computers especially for the explosions, they use the same ones they use for all the _other_ CGI. And like I said, it’s all off the shelf software nowadays. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [February 14, 2015, 8:11pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/16 "2015-02-14T20:11:38Z")
The very best explosions are still real fuel enhanced explosions, but CGI has recently turned the corner. Totally generated explosions are virtually indistinguishable from the real thing, and will cost far less to produce than the real thing, so expect CGI to totally take over soon. To film an actual explosion you need the set, props, a crew, explosives certified technicians, insurance, permits, explosives, fuel … by the time you are done it could easily cost $10,000 to film a tiny explosion. The cost of the CGI is virtually nothing, paying one animator for a day, and they work cheap because they think it’s such a cool job. ---
**Author:** ![HipGnosis](https://avatars.discourse-cdn.com/v4/letter/h/76d3ee/32.png) [@HipGnosis](https://boards.straightdope.com/u/HipGnosis)\ **Post date:** [February 14, 2015, 8:29pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/17 "2015-02-14T20:29:23Z")
It’s called ‘special effects’ because the directors don’t want ‘realistic effects’. ---
**Author:** ![Qwertol](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Qwertol](https://boards.straightdope.com/u/Qwertol)\ **Post date:** [February 16, 2015, 12:48pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/18 "2015-02-16T12:48:24Z")
> [@TriPolar](#): > > The very best explosions are still real fuel enhanced explosions, but CGI has recently turned the corner. Totally generated explosions are virtually indistinguishable from the real thing, and will cost far less to produce than the real thing, so expect CGI to totally take over soon. To film an actual explosion you need the set, props, a crew, explosives certified technicians, insurance, permits, explosives, fuel … by the time you are done it could easily cost $10,000 to film a tiny explosion. The cost of the CGI is virtually nothing, paying one animator for a day, and they work cheap because they think it’s such a cool job. Yeah, you can simulate flames quite realistically now, but explosions usually involve flying debris and simulating those can be quite difficult (it requires realistic lighting, shadows, physics and so on…). I bet it is still cheaper to do the thing for real than to hire experienced CGI special effects company… ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 16, 2015, 8:49pm UTC](https://boards.straightdope.com/t/how-they-make-movie-explosions-so-fiery/712617/19 "2015-02-16T20:49:15Z")
> [@Qwertol](#): > > Yeah, you can simulate flames quite realistically now, but explosions usually involve flying debris and simulating those can be quite difficult (it requires realistic lighting, shadows, physics and so on…). I bet it is still cheaper to do the thing for real than to hire experienced CGI special effects company… Like I said, particle simulators are mature, off-the-shelf software now. I’m no CGI tech, but I could set up a rudimentary exploding house-type scene in Blender in a day. I expect it to be that much easier for an actual trained CGI technician, using commercial software.