The first ingredient of any firework is the ancient explosive black powder, made by 75% potassium nitrate, 15% charcoal and 10% sulfur. Once lit with a fuse or spark, the sulfur melts first at 112.8°C. The sulfur flows over the potassium nitrate and charcoal, which then burn. This combustion reaction quickly produces a large amount of energy and gas – in other words, an explosion. There are a number of different elements that, when added to a firework and heated, release different wavelengths of light that appear as different colors. Strontium makes red. Barium produces green. Copper burns blue, and so on.