If you’ve ever wondered how sparklers work or why they don’t burn when you put your hand near them, the American Chemical Society’s ACSReactions YouTube channel has you covered.

The gist is that at the tip of a wire is a paste with a metal-based fuel and an oxidizer, a molecule that gives off oxygen when it burns. This helps keep the sparkler lit. The sparks are little pieces of flaming metal, and the color comes from a colorant like strontium, magnesium or copper which burn red, white and blue.

The shards of flaming metal shooting off the sparkler don’t burn your hand because they’re far too light. Still, the thought of thousand-degree metal bits shooting off of an iron wire makes you wonder whether you should keep substituting sparklers with candles in all those birthday cakes…