Firework Colors: Metal Salt Flame Test (3D)

Metal Salt

Primary metal Strontium (Sr)

Blend with None

Mixture ratio (A ↔ B) 100% A

Combustion

Flame temperature 2200 K

Fuel / oxidizer amount 60%

Click anywhere in the sky to launch another burning star with the current salt mix.

Live Emission

Bright red

emitted color

Peak λ (A)

650 nm

Peak λ (B)

—

Excitation / brightness

54%

Stars aloft

Why temperature ≠ color

Combustion heat excites the metal ion's outer electrons to higher, discrete energy levels. When an electron falls back down, it emits a photon whose energy — and therefore wavelength/color — equals the exact gap between those two levels. That gap is a fixed property of the element (Sr ≈ 650 nm red, Ba ≈ 524 nm green, Na's D-line ≈ 589 nm yellow, Cu ≈ 505 nm blue-green, Ca ≈ 618 nm orange, K ≈ 404 nm violet), so no amount of extra heat can shift red strontium toward blue.

What temperature does control is how many ions get kicked into that excited state per second (Boltzmann population), and how strong the underlying blackbody glow of the hot solids is — both raise brightness, not hue. This is exactly how firework formulators and astronomers use flame/spectral emission lines as an element fingerprint, independent of how hot the source burns.

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