Kids Learning · science · ages 7-11
How Do Fireworks Get Their Colors?
Why fireworks are red, green or gold, why you see the burst before you hear the boom, and why blue is the hardest color to make.
Have you ever watched a fireworks show and wondered how the sky turns red, then green, then sparkly gold? It isn’t paint and it isn’t magic. It’s chemistry!
The color recipe
Inside every firework shell are little pellets called stars. Each star has a pinch of a special metal mixed with things that burn very hot. When the star burns, the metal heats up so much that it gives off light, and every metal glows its own color:
| Color | Metal inside |
|---|---|
| Red | Strontium |
| Orange | Calcium |
| Yellow | Sodium (the same element that is in table salt) |
| Green | Barium |
| Blue | Copper |
| Purple | Strontium and copper together (red + blue) |
| Gold and white sparkles | Iron, aluminum or magnesium |
Why blue is the hardest
Copper makes blue, but only if the temperature is just right. Too hot and the blue fades to white. Firework makers worked on blue for a very long time, so the next time you spot a deep blue burst, you’re seeing something tricky!
See it first, hear it later
When a firework bursts, the light reaches your eyes almost instantly. The sound is much slower: it travels about 1 kilometer (0.6 miles) every 3 seconds. Try it at the next show: count the seconds between the flash and the boom, then divide by 3. That’s about how many kilometers away the firework is!
Try this at home (no fire needed)
Look at the videos below and make a list of every color you can spot. Then use the table to guess which metals were in each firework. How many different metals did the show use?
Watch and look closely
Check what you learned
What gives a firework its color?
Each metal glows its own color when it gets very hot, like a secret recipe for every color.
Which color is the hardest to make?
Blue needs copper, and copper's blue glow fades if the firework gets too hot, so it is tricky to get just right.
Why do you see a firework before you hear the boom?
Light reaches you almost instantly, but sound only travels about a kilometer every 3 seconds.
Strontium makes fireworks glow which color?
Strontium makes the bright reds. Barium makes greens.