Copper chloride is the pigment that gives fireworks their blue hue. Blue light is produced when copper salts and chlorine sources are mixed to create copper(I) chloride. But copper chloride is brittle and begins to decompose at about a thousand degrees Fahrenheit, which is a problem for pyrotechnic formulations. Since a viable substitute has not been discovered, copper chloride continues to be the major ingredient used to make blue fireworks, despite its fragility. To overcome the drawbacks of copper chloride, substitute methods have been devised, such as the use of copper(I) iodide or copper(I) bromide in chlorine-free pyrotechnical mixes.
These other options entail adding more chemicals to improve the blue light's spectral purity. Although copper chloride is the main ingredient in blue fireworks, its brittleness and the potential formation of carcinogenic polychlorinated compounds have led to efforts to develop safer and more stable alternatives.
