Why some flames are blue and others are red?

Full video: https://www.youtube.com/watch?v=1pfqIcSydgE Chemistry may tell us the recipe for combustion, but the light show is all physics. When a flame burns cleanly (like a gas flame, blowtorch or the base of a candle), the heat excites the molecules to release light (usually pale-blue) from atomic transitions. That's quantum mechanics! Now when the fuel isn't as pure and doesn't entirely burn (like a wood fire or coal fire or the top of a candle flame), there's still some blue light, but you