Exploding The Mystery Of Blue Fireworks

AUDIE CORNISH, HOST:

If you're watching fireworks tonight, here's how you can tell you're looking at a top-shelf display and not some cut-rate carnival sideshow. Look for the blue fireworks. Are they true blue, not pale or purple or mauve?

The color blue has been the Holy Grail for pyrotechnics experts since fireworks were invented more than a millennium ago. It's by far the hardest color to produce. But why? For that, we turn to John Conkling. He's technical director of the American Pyrotechnics Association. John Conkling, welcome.

JOHN CONKLING: Thank you. It's nice to be with you.

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CORNISH: So begin by telling us, what makes the color blue so difficult to replicate in fireworks?

CONKLING: Well, you need the correct chemistry. And for the color blue, the emitter, the chemical species that produces a blue light up in the sky is a fragile copper compounding, a gas. And then you heat it to very high temperature, and it gives off light. The particular light that copper emits at high temperature is blue. But if your temperature gets too high, you lose the color. You wash out the color. It stops emitting. If the temperature is not high enough, you don't get any type of intensity, so you need a perfect flame temperature.

CORNISH: And I understand that, of course, you need certain elements to create certain colors and, of course, reds and oranges and things that are similar to the colors of fire are a lot easier to produce.

CONKLING: Yes. The red color, the green color, the orange color, white, very, very easy to produce. They've gotten a lot better in recent years because, again, new chemistry using metal fuels has raised their flame temperature, which makes the color brighter, but you can't do that with blue because you wash out the color. So even at best, your blue is going to be dim if you compare it to the current reds and greens and some of the other colors that are out there now. They're much, much brighter.

CORNISH: Now, like we said, it's been more than a thousand years since the Chinese invented fireworks. And do you think at this point we could have found a way to make blue easier for everyone?

CONKLING: Well, people have been trying for decades and decades and decades. And to this point, nobody's found the perfect chemistry to get that bright blue that everybody would love to see up in the air.

CORNISH: Now, do most folks really notice this or is this something that's kind of a hobby for the pyrotechnics world?

CONKLING: Well, it's something that people who have really been involved with fireworks look for when they watch a show. But for the average person watching our Fourth of July show, the other colors that are out there, the patterns they produce, the effects they shoot up in the air, the timing, it just is so overwhelming that there - I think very few people who leave the show saying, boy, I wish I'd really seen a good blue.

CORNISH: Well, John Conkling, thank you so much for speaking with us.

CONKLING: Well, it's been a pleasure and hope everybody has a great Fourth of July.

CORNISH: John Conkling is technical director of the American Pyrotechnics Association.

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CORNISH: You're listening to ALL THINGS CONSIDERED from NPR News. Transcript provided by NPR, Copyright NPR.