Inside a fireworks display

Ever wonder what goes into a professional fireworks display?

We asked Joel Scarbrough of St. Gabriel, who has a license to burn. More specifically, a Pyrotechnic Operator’s License, which means he knows all about fireworks displays.

Here are a few things to think of next time you’re gazing up at an exploding sky.

Rockets, shells and firecrackers. They’re the basic types. Rockets and shells go up, firecrackers stay on the ground.

Shells are essentially two cardboard halves completed individually and wrapped together. A lift bag of black powder propels a shell. For a show, shells are placed into guns or mortars built not to disintegrate into dangerous flying shards.

Inside a shell are marble-like objects called “stars.” Bigger stars burn longer, and their colors come from various compositions applied by the manufacturer. Copper compounds and chlorine producers, for example, make blue.

Many fireworks in a display are arrayed in “cakes”—boxes of tiny pre-timed mortars. A technician lights a master fuse then gets the hell out of the way. A common consumer cake may have 32 shots, while a display cake can have as many as 660.

Many firework effects are named after flowers. A “peony” is a burning sphere, while “chrysanthemums” have a visible trail of sparks. A “willow” pops and drips down slowly.

To make one shell that may last three seconds during a show takes one person about 40 to 50 hours of work, from manufacturing black powder and stars to making the fuse and assembling the lift bag.

The distance the crowd must be from the firework launch area is determined by the diameter of the biggest shell in the show. According to the feds, that’s 70 feet of distance required per inch, or 840 feet for a 12-inch shell.