Your burning questions about fireworks, answered | KCUR

Fireworks are a staple of Independence Day celebrations, ringing in the New Year, baseball games, amusement parks and backyard hangouts. But what really creates these spectacular displays?

Recently, we asked readers and listeners to send in their burning questions about fireworks, how they’re made and how they’re used.

As a chemistry professor at The University of Texas, and science entertainer who regularly goes on national TV to explain the science behind explosives, I’m happy to sit in the hot seat and find the answers.

I’ve been through several pyrotechnic training sessions and am certified to play with explosives. So let’s start with the basics.

Where do fireworks come from?

We think firecrackers were invented in China as far back as 200 BC, possibly when bamboo was left to dry for too long over hot coals. Apparently, if left unattended, the bamboo can dry out and “crack,” making a sound loud enough to scare away intruders, and some believe evil spirits.

In 800 AD, a backyard chemist searching for “eternal life” mixed together potassium nitrate, charcoal, and sulfur. Unfortunately, he didn’t find the answer to immortality, but he did find the recipe for gunpowder. And it didn’t take long for people to learn that bamboo tubes stuffed with gunpowder made for a feisty little sparkler.

Over time, the military attached arrows to the sparklers to create a whole new type of weapon. But in their free time, Chinese soldiers turned their rocket cannons toward the sky to enjoy the first aerial fireworks.

By the year 1600, full firework shows were in effect. They were managed by “firemasters” and performed by their “green men” assistants who earned their descriptive nicknames from the leaves they wore to protect their bodies from the sparks.

Then on July 4, 1776, the United States declared its independence from Great Britain, and celebrated it with what John Adams referred to as “illuminations,” an antiquated word for fireworks.

As far as historians can tell, we’ve kept the tradition alive by using fireworks to celebrate every Independence Day thereafter.

How do fireworks work?

In contemporary fireworks, the fuel source is called “black powder” and it’s made from charcoal, sulfur, and potassium nitrate.

It first operates as a “lift powder,” the fuel that propels the firework off of Earth’s surface. At the same time, this ignition starts a time-delay fuse.

If things go just right, when the firework reaches the perfect altitude, that fuse ignites another portion of black powder called the “break charge.”

This second explosion scatters “pyrotechnic stars”, which look like little rodent food pellets, into the atmosphere. The stars contain an oxidant (often potassium perchlorate) that decomposes and then releases oxygen gas. The charcoal and sulfur in the black powder immediately react with the oxygen in the “pyrotechnic stars” in a high-temperature combustion reaction to give us the desired BOOM.

Up until the 1830s, all fireworks were orange. It wasn’t until Italian inventors started adding metals to the pyrotechnic stars that we began to see fireworks in reds and greens.

Strontium burns red, copper gives us more of a blue/green color, potassium is pink and sodium has an orange/yellow hue. Whenever you see a crackly bright white, you know that the star contained magnesium.

What causes the unique smell of fireworks?

The aroma of fireworks has been described as a classic sulfur “rotten eggs” smell, mostly due to the presence of hydrogen sulfide.

You might also detect a “horse stable” smell (from ammonia), or a sweet aromatic scent (from carbon disulfide), or possibly even a hint of vinegar (from sulfur dioxide.)

What are the negative side effects from fireworks?

There’s no skirting around the fact that fireworks are not great for the environment. They release carbon dioxide into the environment, ultimately exacerbating our ongoing battle against climate change.

To make matters worse, they produce particulate matter and pollutants. When these particles are inhaled, they can cause adverse health effects — especially for the respiratory and cardiovascular systems.

And on top of all this, the amount of light and noise pollution is also concerning. A study out of Portugal found that at every single event evaluated, the exposure level exceeded 120 db — which is the recommended noise limit for children. At 78% of these events, it exceeded 140 dB, the recommended noise limit for adults.

Depending on geographical factors, fireworks can reach sound levels of 190 dB.

There is a new trend of drones shows for a quieter, more environmentally friendly option. But it hasn’t completely replaced the traditional fireworks display yet.

So, do the smart thing and bring some ear protection the next time you go watch fireworks – especially if you bring your little ones along.

And please leave your dogs at home. We all know, these loud sounds can really stress them out.

How much do fireworks cost?

At home (if they’re legal where you live) you could set off nine pretty decently sized fireworks for around $200, and that would last for about half a minute.

For a professional show, it will be closer to $1,200 per minute.

Really big shows like the Macy’s Fourth of July Firework Spectacular is estimated to cost $6 million.

But at home you can still find smaller fireworks that won’t break the bank like snakes, poppers, snapsand sparklers for under $5.

That being said, firework laws differ from state to state. Some cities even have their own set of rules, so be sure to double check where you’re allowed to actually set off fireworks.

What do I need to do if I want to blow stuff up for a living?

This is a great question, and the answer is simple. Study hard and pursue a career in STEM. My route started with a passion for chemistry, and a flair for a little drama.

If you want to become a backyard chemist, consider attending a training that will allow you to be part of a fireworks display crew. Or take it to the next level, and get your pyrotechnic operators license. The process is unique to each state.

And please listen to me when I say this: Do not mess around with fireworks. They are seriously dangerous.

There were over 120,000 firework-related injuries in the United States from 2012-2022. Most people injured were between the ages of 20-24, and the majority of them were men.

Have fun this July 4, but please do not play with illegal fireworks. Leave it to the professionals!

Want to know even more about fireworks? Listen to the latest episode of the KCUR Studios podcast Seeking a Scientist.

Additional sources from Seeking A Scientist:

Seeking A Scientist is a production of KCUR Studios. It’s made possible with support from the Stowers Institute for Medical Research, where scientists work to accelerate our understanding of human health and disease.

It’s hosted by Dr. Kate Biberdorf, AKA Kate the Chemist. Our senior producer is Suzanne Hogan. Our editor is Mackenzie Martin. Our digital editor is Gabe Rosenberg.

This episode was mixed by Suzanne Hogan with support from David McKeel, Zach Perez, Byron Love and Genevieve DesMarteau.

Our original theme music is by The Coma Calling. Additional music from Blue Dot Sessions.

This content used audio featuring KCUR listeners, sourced through our station’s texting services. Learn more and sign up here.