Part V: Flame Spectra of Blue Color Compositions

ABSTRACT: We can see three different flame colors (i.e., blue, light green and reddish orange) when we insert a small copper piece into a flame of a burner. The blue color is caused by CuCl bands with the strongest lines between 4269–4560 Å. Our goal is to use this color for fireworks. Blue is produced by some copper salts or copper metal powder in the presence of chlorine or hydrogen chloride gas, but if the concentration of gas is small, the blue color is interfered with by the light green color, which seems to be caused by a continuous spectrum of other copper chloride bands (5263–5531 Å).

The flame spectra are examined under various conditions. For low temperature flames, ammonium perchlorate is the best oxidizer and produces an excellent bright blue. For high temperature flames it is necessary to decrease the percentage of magnesium powder, because the CuCl bands seem to  dissociate with increasing magnesium.

Ref: Selected Pyrotechnic Publication of Dr. Takeo Shimizu, Part 3,  pp 87-102

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