Buildings and Cars

Movies often require a building to be blown up. The type of explosions described previously do not have the ability to blow up a building themselves, so pyrotechnics are able to make it appear as if a building is being demolished without actually hurting the structure. There are some cases though when the destruction of a building is needed, such as the hospital in Dark Knight. For these types there are two parts to the explosion, the "cosmetic" and the damage inflicting.

The structure is first weakened to the point where it is barely standing. Explosives are then placed at the remaining support beams. A highly explosive plastic like chord known as Cortex, Prima-Cord or Det-Cord is wrapped around the poles and set to go off at the same time as the "cosmetic" explosions. For the final effect, when the Det-Cord takes out the remaining structural supports, it appears as if the black powder and gasoline devises, that make the explosion look dramatic, caused the building to fall.

Car explosions are done in a similar way. They are gutted to take out all fuel tanks, lines and often times the engine. The doors and hood are taken off and reattached with cable. Often another cable will prevent them from flying off too far, restricting their movement. Multiple charges are then placed to simulate the way an actual car would explode, beginning in the fuel tank. Black powder mortars are used to blast off doors and such while gasoline fire balls give the impression of doing the work.

To cause a car to roll or flip over, an explosive canon devise is used. Part of a telephone pole is fitted to the car, with a black powder bomb above it. The stunt driver then detonates the bomb at the appropriate moment, causing pressure from the black powder to shoot the telephone pole out and propelling the car into the air.