(Image from Daily Disney by Joe Penniston)
Have you ever wondered how fireworks produce various colors in the sky? It sounds easy to produce; however, there is a lot of physics and chemistry involved in making fireworks. Colors in fireworks are generated by pyrotechnic stars usually just called stars, and the stars generally require an oxidizing agent, fuel, binder (which holds pellets together), and color producing chemicals to produce color effects.
Video from YouTube: Basic compositions of fireworks
Color production in fireworks involves two main mechanisms Incandescence, and Luminescence.
Incandescence from fireworks
Incandescence is one of the processes by which fireworks emit light produced from heat.
•The light emitted through Incandescence is produced through extreme heat, which when applied to another chemical compound can cause a bright glow that changes colors (initially emitting infrared, then red, orange, yellow, and white light) as the temperature intensifies. When the temperature of a firework is controlled, the glow of components, such as charcoal can be manipulated to be the desired color (temperature) at the proper time. Metals, such as aluminum, and titanium, burn very brightly, and are useful for increasing the temperature of the firework.
Luminescence from Fireworks
Luminescence is light produced using energy sources other than heat.
• Sometimes luminescence is called “cold light”, because it can occur at room temperature and cooler temperatures, thus it is the low temperatures involved in the process of luminescence that gives fireworks cooler shades of light, emitting instead blue, and green. Luminescence is produced when energy is absorbed by electrons resulting in the electrons going into an unstable state of excitement. As the energy is absorbed by the molecule, the electrons in the atoms rearrange from their lowest energy rate to a higher energy state. When the electron returns to a lower energy state the energy is released in the form of a photon (light). The energy of the photon determines its wavelength or color.
Visible light of different wavelengths is detected by our eyes as a range of colors. Of the light that we can see, red has the longest, and violet has the shortest wavelength.
Image from hueconsultingblogspot
Color producing compounds (Careful formulation is required)
To make fireworks colorful, various metal salts are added to the basic oxidizing agent fuel.
Image (list of fireworks metal salts) from allsparkfireworks blog
(If you would like to see some colorful fireworks, watch this video.) Thank you
Video from YouTube:London Fireworks 2012 presented by BBC.
References:
http://www.pyrouniverse.com/consumer/howtheywork.htm
http://answers.yourdictionary.com/science/how-do-fireworks-work.html
http://www.elmhurst.edu/~ksagarin/color/discussion3-F07.html
http://chemistry.about.com/od/fireworkspyrotechnics/a/fireworkcolors.htm
http://en.wikipedia.org/wiki/Fireworks
http://hueconsulting.blogspot.com/2010/07/how-fireworks-produce-color.html
