Here's why you never see brilliantly blue fireworks

• Bright blue fireworks are far more challenging to produce than common colors like red, white, or green.
• Pyrotechnicians have been trying to produce brilliant blue fireworks for centuries, to no avail.
• The challenge is that the copper compound needed to create that bright color breaks down at the high temperatures needed for a firework to work.
• Meanwhile, the chemicals that make more common colors like red, green, and white are harder to destroy.
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Following is a transcript of the video.

Narrator: Fireworks have been around for millennia. They flood the sky with brilliant bursts of scarlet, emerald, and ivory. But never blue. Pyrotechnicians have tried to produce blue fireworks for centuries, and they have yet to succeed. Why is blue so elusive?

John Conkling: The blue has been very, very difficult to achieve at a level comparable to the greens and reds and whites, just because it's a stability issue at high temperatures.

Narrator: That's John Conkling. He's one of the world's leading experts in pyrotechnics, and he says the problem comes down to chemistry.

You see, to make fireworks, you need four basic components: Fuel, usually gunpowder, a compound that produces color, a fuse, and glue to hold it all together.

You mix this stuff up into what's called a pellet and then shoot it into the air. When the fuse burns up it sets off the gunpowder, which explodes. That explosion heats up those color-producing compounds, causing them to glow.

And it turns out,

Conkling: The hotter you can get the molecules in your flame the more ignition you're going to get, so the brighter and more intense the flame color is going to be.

Narrator: But there's a limit. Because temperatures that are too hot will break down those molecules and wash out the color.

But some molecules are hardier than others. Strontium chloride, the compound used to make red fireworks, can withstand at least 1,500 degrees Fahrenheit. That's hotter than some lava. But to make a blue firework, you need copper chloride, which is much more fragile.

As soon as it gets hot enough to blaze blue, at least 1,000 degrees Fahrenheit, it starts to break down. And even after centuries of searching, we still haven't discovered the right one, nor have we found a more stable replacement for copper chloride. And even if we do, we'd better hope that it's cheap and non-toxic.

Conkling: Arsenic, for example, has been used in some old fireworks formulations, but obviously an arsenic compound is not something you'd want to put up in the smoke where people are watching the fireworks.

Narrator: To be fair, we've gotten close-ish.

Conkling: There are some respectable pale blues that are used in special effects, where the audience is closer to the action, where the color is more visible. But it's been a long search, and we're not there yet.

Narrator: But there's still hope for bright blue.

Conkling: Certainly it's possible. There are a lot of people working on it. There could be a breakthrough one of these days.

Narrator: And even if we never find that brilliant blue, there's still plenty to get excited about on the horizon, like fireworks that burst into different shapes and patterns, even letters. So maybe one day we could see an American-flag firework for the Fourth of July.

We just need to get that blue.