What’s in that sparkler that burns so bright? That’d be incredibly hot-burning chemicals, mainly.
The ingredients of a sparkler are pretty basic. You need some kind of fuel, an oxidiser (either iron or steel powder), a binder, and wire. According to Rensselear Polytechnic Institute, the most common mix is charcoal and sulphur as fuel, potassium nitrate as an oxidiser, and sugar or starch as a binder.
If these components sound familiar to some of you firebugs out there, yes, they’re also the same components in fireworks. The difference is in the proportions, not the ingredients themselves. The colour mix of the firework or sparkler also varies the exact composition a little, as this chart from Compound Interest breaks down.
Image: Compound Interest
Different colours aside, it’s the same relatively simple formula of wire, fuel, and oxidiser over and over again. In fact, if you’re so inclined, the internet abounds with vaguely alarming DIY sparkler recipes that you can use to mix up a batch yourself.
But be forewarned: Just because at-home versions are possible doesn’t mean sparklers are harmless. Far from it. Temperatures of a burning sparkler can reach over 1000°C. Gloves and buckets of water at the ready, of course.