(c) Anthony K. Grafton 2003

Fireworks of Many Colors

“How do they make fireworks explode into different colors?”

Dylan Barber, age 10

Campbellsville, KY

Thank you for your question Dylan. There are two ways that fireworks can produce light: incandescence and luminescence.

Incandescence is easy to understand: when things get very hot, they glow brightly. Depending on how hot something gets, it will glow with different colors. First it will glow red or orange, and as it gets hotter it will shine with a yellow or white light. Astronomers can even tell how hot stars are by looking at their colors. Some fireworks are made to burn at different temperatures, and therefore they produce different colors. Think about the difference in the color of a glowing match and the color of a burning sparkler. The sparkler burns with a bright yellow or white light because it is much hotter than the match.

To understand luminescence, we need to first think about how atoms are put together. Atoms are very small and make up everything around you. Atoms themselves contain three kinds of particles: protons, neutrons, and electrons. Protons and neutrons are concentrated in the center of the atoms and form what is called the nucleus of the atom. Electrons orbit around the nucleus in a way that people sometimes compare to the way planets orbit around the sun.

Sometimes electrons absorb energy from the surroundings and move farther away from the nucleus. Later, the electrons release this energy and return to an orbit closer to the nucleus. The energy they release is given off as light in a process we call luminescence, and atoms of different elements will give off light of different colors. Fireworks can contain atoms of elements that, when heated, will produce different colors through this method of luminescence. Elements such as strontium and calcium are used to produce red and orange colors, while barium and copper can produce green and blue colors. Because atoms of different elements produce different colors when they glow through luminescence, scientists can often tell what something is made of by observing the colors that are produced when a sample of it is heated.