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?
According to Mythbusters, they use gasoline in movie explosions. That is how they make the big fireballs.
Lots and lots of gasoline. Plus kerosene for the roiling extra black smoke.
In Independence Day (ID4) the pyrotechnicians used propane diluted with CO2, and chunks of cardboard for flying debris.
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. 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.
Dateline NBC got some really good explosions with simple pyyrotechnics.
I read somewhere long ago that naphtha was was useful for fiery explosions.
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.
Also, note that the pyrotechnics were under a large tank of gasoline.
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.
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.
And much more fun. 
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.
We have the physics of this sort of thing down quite well now, with off-the-shelf particle and other modellers, so explosions are easier than ever before.
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.
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.
It’s called ‘special effects’ because the directors don’t want ‘realistic effects’.
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.