Cool colored candles, with metal salts from our rocket propellants

The birthday month Marches on!

These special candles on my cake are really cool. The flame colors are just like the propellant colors we have in our solid rocket motors. Metal ions combine with electrons in the flame, and the metal atoms are raised to excited states because of the high flame temperature. Upon returning to the ground state, they give off a pure wavelength of light (from their line spectrum) characteristic of that metal.

The ions come from metal chlorides: Barium Chloride (BaCl) for green, Copper Chloride (CuCl) for blue, or Strontium Chloride (SrCl) for red. Here is a primer on rocket propellants with photos of my rockets flying with the various colors.