This is the biggest, brightest, hottest video there is about the science of fireworks. This video is brought to you by Kiwico – go to https://kiwico.com/veritasium for your first month free!

If you're looking for a molecular modeling kit, try Snatoms - a kit I invented where the atoms snap together magnetically: https://snatoms.com

Check out Gene’s channel here -- @PotatoJet 

Massive thanks to Mike Tockstein from Pyrotechnic Innovations @PyroInnovations  
and Will Scott from Las Vegas Display Fireworks Inc, for all your pyro knowledge and keeping us safe.

▀▀▀
Massive thanks to Gene Nagata from PotatoJet for filming this episode – check out his wonderful channel for more videos about cameras and FPV drones.

Thanks to Brandon Williams for helping with the chemistry and sourcing of materials. 

Thanks to Matthew Tosh for the help with the chemistry conversation about fireworks.

Thanks to Simon Werrett for the help with the history of fireworks.

▀▀▀
Werrett, S. (2010). Fireworks: pyrotechnic arts and sciences in European history. University of Chicago Press

▀▀▀
Special thanks to our Patreon supporters:
Emil Abu Milad, Tj Steyn, meg noah, Bernard McGee, KeyWestr, Amadeo Bee, TTST, Balkrishna Heroor, John H. Austin, Jr., john kiehl, Anton Ragin, Diffbot, Gnare, Dave Kircher, Burt Humburg, Blake Byers, Evgeny Skvortsov, Meekay, Bill Linder, Paul Peijzel, Josh Hibschman, Mac Malkawi, Juan Benet, Ubiquity Ventures, Richard Sundvall, Lee Redden, Stephen Wilcox, Marinus Kuivenhoven, Michael Krugman, Sam Lutfi.

▀▀▀
Written by Derek Muller
Edited by Trenton Oliver
Animated by Ivy Tello and Fabio Albertelli
Filmed by Derek Muller, Hunter Peterson, Gene Nagata, Raquel Nuno
Production by Hunter Peterson and Stephanie Castillo
Additional video/photos supplied by Mike Tockstein/Pyrotechnic Innovations
Music from Epidemic Sound & Jonny Hyman
Produced by Derek Muller, Petr Lebedev, Emily Zhang, & Casper Mebius

This is the biggest, hottest, and most explosive video on fireworks ever.

Covering everything from the invention of gunpowder, to how fire can burn underwater, how fireworks are made, the colors, shapes, fuses, to how they're launched.

I cannot believe the precision with that huge camera on there.

Gene is gonna try to fly the FPV drone actually like through the fireworks as they explode.

Gene makes a channel called Potato Jet and he does tech reviews, but also lots of very filmic stuff.

Are you willing to fly this into a firework as it's exploding?

But we set it up just for that, so I think we can get it.

The first recorded instance of something like a firework occurred in China over 2, 000 years ago, where people would get a piece of bamboo with the ends closed and they would throw it in a fire.

So as it heated up, everything inside would get hot and expand and eventually burst, creating this bang, which they thought scared off evil spirits.

Then they developed black powder and they put black powder inside the bamboo to make an even bigger bang.

I want to test out the earliest known recipe for gunpowder.

It involves 3 ingredients that you can find out in nature.

The first is potassium nitrate, which actually comes from bat and bird guano.

Once they poop in the cave and it dissolves in water, you get these white crystals coming out.

These yellow crystals you can just find on the side of hills or around thermal vents.

That is the major fuel for the gunpowder.

What people observed was when they heated up this mixture, it would spontaneously catch fire.

I have no idea how big of a thing this is gonna be.

This is only about a gram of it, so I don't think it's gonna be huge.

As we heat up that very primitive gunpowder, we should see it burst into flames.

Now that took a long time before we saw the fire, so why is that?

Well, honey contains a lot of water and that's gonna slow down the rate at which this is gonna start to combust.

People figured out that a better fuel was charcoal.

There are 3 things you need to make fire.

In most fires, the oxygen comes from the air, but in gunpowder, the oxygen is supplied by 1 of the solid ingredients.

The potassium nitrate gives you the oxygen, it's KNO3, so there's a lot of oxygen in here.

And then the charcoal provides the fuel, that carbon.

Charcoal is basically just carbon, but it works better than other forms of carbon, like graphite, because it contains these microscopic pores.

And that enables the reactants to mix much better.

They can actually get inside those pores.

So if you mix potassium nitrate with the fuel, charcoal, and add heat from a lighter, you should have all the ingredients you need to make fire.

It seems like little bits of it are catching on fire and just like sparking up from there.

But the trouble with this reaction is that it has a high activation energy, so it needs a lot of heat to get going.

I can see little balls of molten stuff in the crucible there.

So we do have oxygen and fuel and we can get that reaction, but it's just not a very explosive reaction.

Sulfur starts reacting with the other ingredients at lower temperatures, and those reactions give off heat.

It's gonna create that initial bit of heat that potassium nitrate needs to really break it open and then you know everything can react.

So that's what I want to do I want to try to mix sulfur potassium nitrate and charcoal which is like your quintessential recipe for gunpowder and The amounts that you need of this have been pretty stable for like 800 years, which is about 75% potassium nitrate,

Those are the right mixtures so that you have just the right number of each type of atom to fully react and release the most energy possible.

So I wanna test how long it takes for fire to burn down about a meter of this homemade gunpowder.

The granules of charcoal that I've got and these grains of potassium nitrate, even the sulfur, they're all a bit big, so to actually get that reaction to happen fast, It's not really working.

So what I want to do is compare that to store-bought gunpowder from, you know, a factory that's actually ground up all those particles to be really tiny so all the reagents are really close together.

The chemical reaction that occurs in the combustion of gunpowder is complicated, to say the least, but a number of the products formed are solids, and that's why burning gunpowder creates a lot of smoke.

The neighbors have got to be looking at this and being like, what the...

The thing about gunpowder is if you burn it when it's just exposed to the air it doesn't really explode and I think of gunpowder as explosive.

But in order to see that, what you have to do is confine it.

Because when you confine gunpowder, you increase the concentration of all the reagents.

They don't just blow away from each other when they catch fire, so They're forced into closer proximity so they react more.

So the reagents get moving faster, they have more energy, and so they can react more readily.

So I put 10 grams of gunpowder in a cardboard tube and taped it shut.

Okay, that's better, but it wasn't as big of a bang as I was hoping for.

Oh, it was a bit more of a pop than a bang.

So I'm gonna use some fiber reinforced tape to strengthen the container, and then we should get a bigger bang It's more of a bang that's a bit more like it here I have 20 grams of black powder so I guess the question is with twice the black powder do we get twice the bang?

I mean, fireworks consist of a shell with a lot of gunpowder inside.

It's colorized so that you can see the individual pieces better.

A real shell, everything in here would be black because it would be primed or covered with black powder.

For a long time, the terms gunpowder and black powder were used interchangeably.

But these days, the formula for gunpowder has changed to make it smokeless.

So what's used in fireworks is called, at least in the US, black powder to distinguish it from modern smokeless gunpowder.

Just know that in this video we'll use both terms to mean basically the same thing.

The shell itself is made out of cardboard and what looks like and is a form of paper mache with craft paper and a glue and you go around and around once you put the 2 shell halves together.

Is that like the standard size you'd see when you go out?

So on a 4th of July display you'll see anything from 2 and a half inch up to 5 inch typically.

In most cases, 6 inch and above are reserved for locations that you have a huge property, you're out in some desert shoot site, or on a barge somewhere, but they can go even bigger than this, up to 12 inch, 16, and even larger in very special occasions.

This is the hemisphere for a 16 inch diameter aerial shell.

The biggest aerial firework ever was 1.44 meters wide and it weighed about the same as a car.

To launch a firework into the air, the way it's done is with more black powder.

In a typical shell, you're gonna have a baggie of black powder that's underneath the shell, and that acts to fire the shell out of the mortar to the 800 feet in the air, which is what this eight-inch shell would go to.

Shells as large as, say, a 16-inch, those can use literally pounds of black powder underneath them.

To ensure the shell goes straight up, it's placed in a big plastic tube called a mortar.

A pyrotechnician gets 2 bangs for every 1 the audience does.

You get a bang when the mortar fires and then a bang when the shell explodes.

It's literally like a cannon shooting a cannonball in the air.

So the audience doesn't get to hear, see, or feel that, but the pyro crew does.

Does everything burn up before it reaches the ground?

So all the stars, the burst, all of that stuff.

That's why we have a fallout zone, what we call it, or the exclusion zone, where only the crew is allowed with all their PPEs because you do get debris that comes down.

It literally sounds like rain at the end from all of the debris from the finale shells going off all at once.

You'll have a wooden rack with a few HDPE, high-density polyethylene mortars in it and that particular material is meant to expand and split from the energy of a malfunctioning shell versus explode and throw shrapnel everywhere.

We actually experienced an incident like this with the biggest shell we had set to launch.

That 1 did not look like it That's what happens when a firework doesn't lift.

But because we follow all the rules and regulations at a professional display, it's usually the crowd going, whoa, and the crew going, whoa.

It's typically what happens after a few safety checks when something like that goes on.

Thankfully, everyone was safe because we could trigger the fireworks remotely from outside the blast radius.

But igniting explosives safely has long been a

And the mining industry, their delay method back then was to literally sprinkle out a trail of black powder through the mine to give them a delay to the dynamite.

The simplest fuse just consists of cotton string that's been soaked in black powder and then allowed to dry out.

That alone would burn 2 to 3 seconds an inch.

But once you encase it in craft paper, that's literally all this is, You change that burn rate from a couple seconds an inch to anywhere from 30 to 100 feet a second.

This has the same effect as containing the black powder.

It traps in the heat and reagents, so the reaction goes much faster.

This is actually how we shoot our finales so fast.

We're not actually pushing buttons that quickly.

This type of fuse is appropriately known as quick match.

Now, before I'd ever seen quick match in action, it was suggested that I try to race the signal down the fuse.

What I'm gonna do is light this little piece of black match right here And I'm gonna try to race the signal to the other end, but still I was not prepared for what came next You are kidding me!

You didn't tell me it was going to do that!

The force of the combustion products causes the quick match to whip around wildly.

It's crazy how much just containing the reagents and containing the heat from the reaction accelerates it.

It certainly burns much faster than the black match without the paper.

Man, every time, every time that gets me.

1 problem with these basic fuses is they aren't waterproof.

Even though they contain the fuel and the oxidizer, so they don't need the oxygen in the air to burn, they do need heat.

And water is just too good at conducting the heat away from the fuse so it snuffs out the reaction.

The same problem occurs with road flares.

I thought since the flame comes out with such high pressure, it might be able to stay lit underwater.

And it did for a little while, but eventually the water got in there and stole the heat.

So I think that the water is putting it out by pulling the heat away from it, so it doesn't have enough energy to keep burning.

There are special flares made for underwater applications, but even those have similar problems.

You can see the gaseous combustion products being released here and bubbling to the surface.

And while this flare lasted longer, the water still eventually put it out.

But it is possible to make a waterproof fuse.

You're going to see this in a lot of your consumer fireworks.

It's really got a powder core with a fiber wrap to it.

And it's typically lacquer coated, so these fuses are typically waterproof.

Fuses are not only used to light fireworks, they are a core component inside a firework.

So that quick match flashes really quick down into the black powder lift.

That ignites, and while it's pushing the shell out of the mortar, it lights the time fuse.

So this is what would actually be in the shell to give you the time delay from the time the lift charge fires to the time the shell hits apogee and explodes in the sky.

You know, it's about a quarter inch in diameter and is really a black powder core rigid fuse compared to the more flimsy VSCO type.

It's really important that the time delay fuse keeps the combustion contained inside it, so the firework only explodes when you want it to, at the very peak of its trajectory.

These function by not spitting any fire out the side so that the shell doesn't get lit prematurely.

So you should only see it spit out the end once it's made it's all the way through.

Like what kind of material is containing it?

Well, there's a number, there's, there's weaves of fibers in there and a layer of asphalt that really provides that waterproofing.

So you can kind of see how the signal is progressing.

You can see how the fire is progressing through there.

Some of the gaseous products are coming up.

That is all that is needed to ignite the core of a firework

So after that time fuse hits its end, it'll light a piece of black match that'll then flash into the burst charge.

So, that's what's represented by this blue material which is typically rice holes or something similar to that coated with black powder.

like, they're making rice hulls, like donut hulls.

The reason we coat rice hulls is because you get a very granular powder in the center of the shell now, which allows the flame to propagate very quickly through the shell, igniting everything simultaneously, creating that significant overpressure very quickly to blow the shell open.

So a traditional peony shell would be your most basic of fireworks, where these stars would literally be lining the hemisphere, and then you'd have your burst in the middle.

And that would give you a very symmetrical round sphere in the sky, your traditional firework that you see.

But it's just interesting to think that when you see a firework go off, You know, all those little points of light are about that size.

But they look, I mean, I would say that they look bigger, right?

Pretty quick and it is definitely trickier when it's dark like this.

Once I go start looking here, I'm like, I'm not sure.

How do you get focused to something that's not there yet and you're not quite sure where it is or where anything is because it's all pitch black.

Because I basically have locked exposure on this.

I didn't realize I was so close to the ground.

I just wanna see what this looks like, you know.

These stars are made of black powder mixed with chemicals to give them different properties.

So Brocade crown star would be the big, bushy, gold tail that you would see in the sky.

So imagine a big, glittering, gold shell.

I can actually see the little pieces coming off and glowing pretty bright right there.

Now imagine those leaving a tail as they fly through the sky.

Often the chemicals mixed into the stars are used to create specific colors.

Each of these stars would be coated with a primer composition, which is a really fine black powder.

The reason for that is a lot of color compositions take more heat to ignite, so they have a higher ignition temperature.

So by coating with black powder, with that primer, you're ensuring ignition of all the stars which then transfer the fire to that color composition.

The colors of fireworks are actually thanks to quantum mechanics.

An element absorbs energy from the combustion, raising an electron to a higher energy level.

And there are only certain transitions which are allowed.

So when the electron drops back down to a lower energy level, it gives off light with the specific energy of that transition, which corresponds to a particular color.

Some elements are particularly well suited to create certain colors.

So as the copper ions go in there, they absorb energy from the fire, from the combustion, and then the electrons drop back down to a lower energy level and they give out that blue light predominantly, and that's why we get such a great blue color.

This is just a little interjection because I was looking at our flame tests and the copper salt tests, you know, anywhere you look, copper fireworks are meant to be blue, like bright blue, but those flame tests look kind of green.

And so I didn't really know what was going on, but I was sitting here playing with my kids with the KiwiCo flame test kit.

I know like they did sponsor this video, but didn't tell me to put a section like this in.

But what I found is that, okay, I'm using a copper salt here, and it starts out green, and then if you leave it for a while, come zoom in here, it starts to get blue.

To get the beautiful blue color, I think you need more heat.

I think it's a higher temperature that we need that we didn't achieve in our flame tests out in the field.

Here we're getting some potassium chloride to give us some violet.

I'm not seeing too much violet, but maybe just a little.

Our pyrotechnician mixed up some color salt and fuel in a mortar.

What's in there is about 2 gallons of methanol with boric acid on this 1.

See all Veritasium transcripts on Youtube

The Hidden Science of Fireworks