Sunday, July 08, 2018

Big Bangs and Squibs: A Physicist Turns Pyrotechnician for the Day

Last week, I got to watch a great fireworks show from pretty close up—because I was part of the team that made it happen! By the end of the day, I had broken all of my nails, was covered in dirt from origins unknown, and had ash in my ears. It was awesome.

In addition to my normal job, I work part time as a pyrotechnician for Zambelli Fireworks, one of the world’s largest fireworks companies. They have been shooting pyro since 1893, and put on over 1600 shows a year. As you would expect, the 4th is the busiest day of the year for Zambelli. Most of you probably watched a fireworks show on July 4th—odds are it lasted between 15 and 30 minutes, maybe choreographed to music. But a lot goes into triggering the big bangs and great explosions: It took about 20 hours to set up our 18 minute, unchoreographed, show. It was a smaller one, put on for a local country club’s 4th of July celebration, but it was still quite a production. There are a number of great articles about how fireworks get their color and what they look like on the inside. I thought it might be nice to talk about the process and technology from the pyrotechnician's perspective.

Shows launch from different platforms, but this one was put together mainly on a trailer. The first step is racking fiberglass tubes, called mortars, of varying sizes. For this show, they were between 3” and 6”, but I’ve worked on shows with up to 8” racks. Each tube has a little hole drilled in it, and this is where the “squib” comes in.

Not a Mr. Filch type squib, but a long yellow one that sparks at the end: a Merriam-Webster listicle reports that a squib is an unexploded firework—and given its use in the Harry Potter series, this is a satisfying idea. Unfortunately, it's incorrect, at least in modern usage: a squib is a firework’s trigger, a wire that has a match tip at the end, used to light a shell. A current is sent down the squib wire, ignites the match, and triggers the fuse on the shell.

"Damp squib" is apparently a common phrase in British english, referring to a letdown when something fizzles out. Point being: wizards are TERRIBLE.
Image credit: Becky Thompson, APS Physics
After the squibs are tied, it’s time to load the actual shells. The first time I shot pyro this was the part that seemed the coolest. Each shell is dropped down its appropriate mortar and then connected to the squib. In a choreographed show, each shell goes in a specific mortar connected to a specific squib, but for this show we just randomly grabbed stuff out of a box. Each shell has a label saying what it is; one said “hat” on it and we spent much of the day wondering what that meant. Some specific shells have three or ten strung together, all hooked to a single squib. When that squib triggers the first fuse, the fire spreads to each of the three in a set period of time. The chains of ten are called “salutes” or “finale chains” and used for about what you expect. Next time you see three go up at once you can be very knowledgeable say “oh, that was a three shell chain. It’s all triggered by one squib” and sound fancy. This leads to a much quicker series of bangs than triggering three in a row. It’s also how shows get that rapid-fire finale. It looks pretty impressive all wired up.

Albeit crazier than a poorly cabled server room.
Image credit: Becky Thompson, APS Physics
One thing I learned pretty quickly is to load mortars back to front. Never lean over a rigged up firework. You wouldn’t even have time to move. I kept screwing this up, but I still have both eye brows and all my fingers. At this point, all the wire ends of the squibs are connected to boxes that will eventually provide the sparks to ignite the pyro. There’s a key you can turn to “off,” “test,” or “arm.” We just hit test at this point. The foil over the top protect the chains from accidentally igniting, tangling, or having a spark jump from one to another. Since the shells will shoot right through the foil, they just leave it on for the show.

This is what 18 minutes of pyrotechnic "oohs" and "ahhs" in the making looks like.
Image credit: Becky Thompson, APS Physics
After setting up the shells on the trailer, it’s time to do the “cakes.” These look nothing like baked goods. Instead, they are boxes with many small shells that are all connected into long chains: One squib will set off the whole cake. The first show I did, I was told that they spread the cakes out since the crowd really went wild for them—and it turns out this is very true. The cakes are pretty darn impressive. The video below is one of the cakes from the show. I don’t know if you can see it, but we were close enough that the ash and sparks rained down on us. One spark from one squib set all those off. In one of the flashes you may be able to see some roman candles: These required a special structure and some hammering of stakes into the ground. They are pretty fun, but not as great as cakes.

The last thing we put together were two “set pieces.” These are specially made structures. That don’t shoot, but flare to life in a flaming design—any type of graphic you might want. The biggest problem was that they come in sections and we had to put them together. This involved us squinting and rotating them, trying to figure out what the Maryland flag looks like in firework form. Can’t you see it? Neither could we. They are mounted on specially built structures—hence the name "set pieces"—which meant using a nail gun and a circular saw (using power tools will never get old). Once we got all this set up, we drove the trailer at least 600 ft away from the crowd, got the ok from the fire marshal, and waited till sundown.

It's not every day you see a flag that's made to be burnt.
Image credit: Becky Thompson, APS Physics
Actually firing these things is pretty darn cool. We went around, clicked each box to “arm”, and tested one more time to make sure all the connections were good; nothing is worse than having a firework not go off. It's not that great from a show perspective, but worse is having to be the one to figure out what to do with an unexploded firework. For me, the scariest part was being right next to racks of shells and turning a box to a setting labeled “arm.” There’s no real way it could go off until the box that triggers the squibs is also set up, but still...being next to a bunch of pyrotechnics and setting something to “arm” required more courage than I thought it would. The system works by radio control. From a kinda safe distance, a tablet with a fireworks app triggers a firing system that radios to the control boxes, which then send a spark down the squib to the shell. The program is set up so that there is a labeled button for each box, labeled with things like “3” and “finale.”

It's a job that every twelve-year-old boy dreams about, but it's a lot of meticulous setup followed by a few minutes of pushing buttons on an iPad. Still, it manages to be awesome in a way that only explosions can.
Image credit: Becky Thompson, APS Physics
After all that, roughly 12 hours of work, actually firing is no harder than making a phone call. I got to push some buttons for the 6” shells, and found out that the “hat” was indeed a cowboy hat-shaped firework. The show was 18 minutes of pure fun. I got to push buttons and watch the fiery fruits of our labor from a serious front row seat.

Cleanup is nowhere near as long as setup, but at this point, after 12.5 hours, it's pretty rough. If there are any unexploded fireworks, the fire marshal gets involved. Luckily for this show, we did a heck of a job and everything exploded. I loved walking back to the trailer and seeing the massive smoking mess that was left. The grounds crew, eager to get out of there, was lining up in golf carts with headlights waiting for us to get out of their way. We loaded everything onto the trailer and into a truck to be thrown away later, tied a tarp over the shells, and went to take down the cakes and set pieces. The set pieces were hard because after burning they were basically a scaffold of ash, most of which ended up on me. A few splinters later, and more than a few curse words, everything was loaded, the trailer was attached to the truck, and we were ready to roll out around 11pm. Long day, but fun show.

The aftermath.
Image credit: Becky Thompson, APS Physics
It is truly a great experience to be behind the scenes at a fireworks show. I can’t wait for more events. Besides using power tools, hearing explosions, and getting covered in ash, my favorite thing was learning I had earned a nickname. I am one of the few, if not only, physicists they’ve worked with and, as per usual, they immediately said “oh, like on ‘Big Bang Theory’?” when they met me. I am now known, appropriately enough, as “Big Bang Becky.” I couldn’t be happier and I cannot wait to do it again.

Rebecca Thompson

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