Happy July 4th!



A few blog posts ago I mentioned that I used to work as a pyrotechnician for a fireworks display company. We'd travel around Michigan, Ohio, and Indiana on the weekends and shoot professional fireworks displays for the local Potato Festival or Muskrat Days or whatever. As we liked to say, we were like carnies with teeth. Of course the week leading up to and including July 4th was the busiest time of the year. Our little operation often had more than 20 crews shooting shows in somewhere in the area. The busy week usually kicked off with a great show in Grosse Point, Michigan, and here are some pictures from the last time I worked that show back in 2002.

It seemed like July 4th would be a good time to write a blog post about all that, since somehow I've never done so before. Plus you can get a little educated about fireworks.

In this first picture, you can see what shells look like. These are Class B explosives, not the Class C fireworks that consumers can buy in some states. (Class A explosives are things like TNT, etc.) Fireworks generally come in two shapes. The Chinese fireworks are usually round and oblong, while Italian and American shells are usually tube shaped (there's a white/gray example in the foreground.) The main part of the shell is round and is formed from a plastic or glued paper hollow sphere which contains the stars which you actually see burning when the shell explodes. Depending on the desired effect, some of these stars are basically compressed gunpowder rocks, while others look sort of like "Combo's" snacks, but instead of tasty pretzel filled with yummy cheese-like substance, they're cardboard tubes filled with compressed gun powder and other chemicals to make color and/or sparkles. (Strontium salts burn red, Sodium salts burn orange, Iron filings make sparkles, etc. The precise recipes are generally closely guarded company secrets.) These stars are packed into the plastic sphere which also contains a time delay fuse that burns slowly. At the bottom of the oblong shape is the lift charge. When the fuse is lit, it ignites the lift charge, (hopefully) shooting the shell out of the mortar and igniting the time delay fuse which begins to burn. At the apogee of the shell's flight, the time delay fuse will burn through to the burst charge, which will explode the shell and light the stars on fire. Then you "ooh" and "aah".


Picture of fireworks shells, cakes, and a strobe from a fireworks show I worked on in Grosse Pt, Michigan, June, 2002. In this picture we see mostly 3 and 4 inch shells and their fuses, though there is a 6 inch shell in the foreground (marked 295). The red and blue wires are squibs, which are used to electronically fire the shell. The box like device with the red paper on top is called a "cake" and contains many tiny half-inch shells which during the show fills in the space between the ground and the large aerial shells with smaller fireworks. The strobe (the yellow tube in the foreground) sits on the ground and blinks on and off with a nearly blinding red magnesium strobe light effect.


Setting up the show, Grosse Pt., Michigan, June 2002. Finale racks (in this picture there are 400 3" shells) are in the foreground and the main body of the display is behind it. The finale shells have one fuse that burns from one end of the racks to the other, lighting each shell in turn (mostly) automatically.


Setting up. Here you can see the mortars more clearly. They're simply very tightly wound cardboard tubes nailed together in wooden racks. (For certain shells we used steel mortars. I still have a set of steel mortars that I use as weight in the back of my pickup during the winter.) The larger racks weigh about 50 pounds and they are coated inside with carbon soot, so this is a pretty tough and dirty job, at least for a chemist like me. Every shell gets its own mortar so that if something were to go wrong the shell is more likely to go up and explode rather than exploding on the ground among the shooters. We call that a bad day, but the show must go on! Here you can see the different sizes of mortars, from the 3 inch mortars in the left foreground, to the 8 and 10 inch mortars sticking up above the others. We shot shells as big as 12 inches, which contain 45 pounds of gunpowder. However, due to site restrictions on this golf course nothing that big could be shot at this site. I'm on the right (well, my butt anyway and what's left of a pair of jeans) and I'm wiring each shell's squib into those blue boards. The boards are then connected to a firing panel and the whole thing is shot electronically. In the old days when I first started, we rarely shot shows electronically, and everything was fired by hand (including those 12 inch shells!). The fuse, which you can see more clearly in the top picture, is cotton string impregnated with glue and gun powder which is then wrapped in brown kraft paper. It burns at a very fast 60 feet per second. When lighting the shells by hand you are actually standing as close to the mortars as we are here in this picture. Since the fuse burns at 60 feet per second and is only a 2 or 3 feet long, there isn't time to run away. So you just turn your back as it fires. In addition to the noise, there's also the smoke and the burning paper that falls on you. So, obviously ear and eye protection is necessary. But the uniform for shooting was jeans, an old t-shirt, and a cotton hat. Somewhere I probably still have t-shirts full of little burn holes on the back. The cotton hat was important because synthetic fibers would melt a hat to your hair.

These pictures show the only part of fireworks shows that I saw for about 10 years. It wasn't until after I stopped shooting them that I actually got to see the shows themselves.

After the show, each mortar is carefully checked to see if anything misfired. Then the whole thing is torn apart and loaded back onto the truck. If we were lucky, we left this site around 3 AM. So about a 17 hour day, for a 20 minute show. Total cost of a show this size was somewhere around 10K, if I remember correctly.

Some fireworks links:

Greener Fireworks
Shortage of Fireworks this year?
Diagrams of fireworks construction

Enjoy the holiday! Go watch some fireworks. But other than sparklers, for safety's sake, please leave the fireworks to the professionals. We'd all really prefer this not happen, OK? Srsly. We used to say that we only worked with Class B explosives because Class C explosives were too dangerous. Really. They're very poorly made and extremely unpredictable. Oh, and be careful of sparklers too (or as I like to call them, flaming deadly sharp fire rods of death.) Oddly enough the only burn I've ever gotten from fireworks was from a sparkler.

And because everyone always asks, the only accident we ever had on a show was when my sister-in-law slipped on some wet grass after a show and broke her ankle.

Posted: Thu - July 3, 2008 at 11:25 AM        

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