"Daddy?" asks your angel, as she stares at the colorful display in the night sky, "What makes fireworks so pretty?"
You start to sweat as other faces in the crowd turn toward you, awaiting an inspired answer.
"Um," you cough, stalling for time. "It's the, um, you know, the fire and the boom and ... hey, who wants some hot chocolate?!?” It doesn't have to be this way. In the waning moments of 2012, prepare to meet this question and explode it in a spectacle of knowledge.
Many people know that heat plus oxygen plus fuel equals fire. But add a few extra materials and that formula now equals fireworks. Aerial fireworks are constructed in a shape that kind of looks like a ball sitting on top of a roll of duct tape. In the bottom is the lift charge. In the middle of the ball is the burst charge. One fuse runs around the whole shebang and another is packed in the middle.
The first fuse ignites the black powder in the lift charge, sending the firework high in the sky. As the lift charge burns it ignites the second fuse which, a few moments later, blows up the burst charge.
So what about those pretty colours? The answer is in the "stars." Inside that burst charge are little balls of fuel, extra oxygen, and metallic salts. When the burst charge goes boom, so do the stars. Some of the super-sparkly white displays come from the light given off by metal as it burns. Other colours come from the salt. When the molecules of certain substances are excited by energy (like the heat from an explosion) they give off different colours of light. The big, fat fancy word for this is luminescence.
You can actually see this for yourself at home using table salt (1). If you have a gas stove grab a responsible adult, tie back any long hair or sleeves and keep kids and pets at a safe distance as you light the burner (2). Now carefully sprinkle some ordinary table salt into the flame (3) to see the change in colour (4).
This might not be the most spectacular display you've witnessed and some might be tempted to drum up some of the "good" (read: illegal) fireworks for a backyard celebration. But aside from their explosive nature, fireworks contain materials that burn at extremely high temperatures , in some cases upwards of 3000 degrees Celsius. They also contain "oxidizers:" Chemicals that release enough extra oxygen that certain fireworks will continue to burn under water.
So leave the sparkly bombardment to the professionals. Besides, it's a lot easier to enjoy the celebration when your biggest worry is the traffic on the way home and not whether you have a fire extinguisher.