Happy fourth of July everyone!  In honor of the USA?¢‚Ǩ‚Ñ¢s independence I thought it would be interesting to make a post on fireworks and the technology behind them.  While at their core fireworks don?¢‚Ǩ‚Ñ¢t seem to have a lot of tech (light fire make boom), there?¢‚Ǩ‚Ñ¢s actually a lot of interesting stuff that goes into the grand displays that we all watch on the 4th.

There are two basic elements to fireworks:  the firecracker and the sparkler.  Firecrackers consist of gunpowder or flash powder wrapped in a tight paper tube.  The firecracker is going to make that big flash and/or boom effect.  Sparklers are a bit more complex, but it?¢‚Ǩ‚Ñ¢s basically a chemical reaction igniting small pieces of metal to create a long lasting and bright effect of sparkling.  Combine these two elements and we have fireworks!

In the past and in fact at many events today the aerial fireworks we see are launched using the time-tested technique of having an explosive ?¢‚ǨÀúlifting charge?¢‚Ǩ‚Ñ¢ that throws the firework itself into the air.  Once in the air the shell will ignite and give us the cool effect.  This technique works well, but when trying to synchronize the show to music to trying to get the exact same location every time there?¢‚Ǩ‚Ñ¢s now a better way.  Companies like Disney are using a newer technique to launch fireworks into the air using, well, air.  Using compressed air the fireworks will be launched out of a pneumatic tube and into the same spot every time.  Since compressed air can be very easily controlled, it?¢‚Ǩ‚Ñ¢s much easier to get the same launching location day after day after day.  This also allows the launch to be precisely controlled on a time basis allowing the firework to be launched into the air at the precise moment it?¢‚Ǩ‚Ñ¢s needed.  This only solves 1/2 the synchronization problem as the actual shell still needs to light on time and the fuse has to have the exact proper burn time.  Nevertheless this process takes 1/2 of the work out of the overall effect and now allows the artists to concentrate on making sure the shell itself it set up properly.

Now that the firework is in the proper location we?¢‚Ǩ‚Ñ¢re left with the pretty effects.  The effect of a firework, red, green, blue, big bang, no bang, etc. is all done by chemists.  By using different metals and different powders the pyrotechnician is able to get the desired effect.  One metal will burn red and short while another will burn blue and longer.  By packing the shell with these metals in a certain way the desired effect will ignite in the air and we have our ?¢‚ǨÀúoooooh?¢‚Ǩ‚Ñ¢ and ?¢‚ǨÀúahhhhhhh?¢‚Ǩ‚Ñ¢.

There are some great articles on fireworks, firework organizations, effects and whatnot in the link list below:  

http://www.skylighter.com/  - Chemicals and books
http://cc.oulu.fi/~kempmp/colours.html  - The physics of colored fireworks
http://www.pbs.org/wgbh/nova/kaboom/  - A kids fireworks web site
http://www.bigfireworks.com/ - Cool fireworks

I hope everyone had a happy and safe 4th!