Thursday, July 5, 2012

Happy 4th!

Fireworks celebrating the Chinese New Dragon Lunar Year for 2012 via *dans
Last night we were out in the San Francisco cold and fog watching the sky explode with color! For our Happy 4th of July post we want to talk about fireworks. But around here we need a bit of science with our color so lets talk about the chemistry of of these beautiful explosive displays. 

Firework fan at Bostalsee via 55Laney69
 Fireworks require two basic components: an oxidizer and a fuel to create an explosion   Black powder, the first firework discovered in China in the 10th Century, is a combination of potassium nitrate, charcoal and sulfur. "You only need the first two ingredients, an oxidizing agent and a fuel, to start the explosion. The oxidizing agent, often a perchlorate or nitrate salt, releases oxygen gas that feeds the fire in a firework. The fuel reacts with the oxidizing agent to create the gas. The sulfur in black powder intensifies and continues the reaction between the other two ingredients."In addition to this basic recipe Pyrotechnicians often add metal salts which are burned in the reaction emitting specific wavelengths of light.

Fireworks Displays at Victoria Harbour, Hong Kong, during Chinese New Year 2011 via Amar_Rai
Melissae Fellet from KQED has a great explanation of the magic of these chemical reactions at the atomic level:
"Heating atoms of sodium, barium or strontium pumps energy into the electrons whizzing around each nucleus. Those energized electrons shoot up to higher locations in the atom. As they fall back down to their usual positions, the electrons lose their extra energy as visible light.
The amount of energy released during this process – which depends on the element – is related to the color of the light that we see. Higher energy, like that released by copper atoms, corresponds to a shorter wavelength of light towards the blue end of the spectrum. Red light from strontium atoms has a longer wavelength and lower energy."

And for a little dash of color: The video features John A. Conkling, Ph.D.,  the author of The Chemistry of Pyrotechnics, Basic Principles and Theory, showing us how different combinations of chemicals create different colors when ignited. Its explosive!

- Emily Eifler, Writer, Colour Studio
- Jill Pilaroscia, Principal, Colour Studio

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