Every year here in the States, we celebrate independence by lighting something on fire. Thanks to the science of pyrotechnics, and care, this can be somewhat safe, but the interesting part about fireworks isn't how much noise we can make with gunpowder. It's all about the colour.
I was surprised to learn that the burst of light and colour is actually the contents of a firework cooling down. When heated, the chemicals involved take on a lot of energy, and when cooling, they release that energy while shining brightly. The base ingredients are black powder, an oxidiser, and a fuel source. The oxidiser provides a higher amount of oxygen than the surrounding that air so that the firework can burn adequately. To get a sort of hands-on idea of what goes on inside the firework, sparklers will show you best.
Pyrotechnic chemists don't want their explode. Although the quick bursts of fireworks shows might suggest a fast burning, it's actually slow burning fireworks that show the best colour. Working with certain chemicals brings out a desired colour. For example, magnesium makes white, strontium makes red, copper makes blue, barium makes green, sodium makes yellow, and calcium makes orange. Just as with paints or dyes, mixing these chemicals can produce a blending of colour, like copper and barium combined to make turqoise and strontium and copper will make purple. The chemicals are produced in pellets about the size of sugar cubes, and blending them together requires an understanding their different igniting points, but the firework can be designed to accomodate for just that.
|Adding a sparkling effect to fireworks requires aluminium, and depending on how hot the aluminium will burn, they can appear as gold or silver, gold being hotter. Magnesium and aluminium can produce the same brightly burning effect. Making two rows of chemicals, instead of blending them, makes a double ring. To make specific designs, like a star, heart, or even someone's face, the pellets are glued to paper arranged in the desired shape.|
Whether you watch a fireworks show on television or on blankets in a field, just remember that there's even more to wonder about while watching in awe.