Sunday, July 7, 2013

P is for... Pyrotechnics

A favorite feature of Canada Day and Independence Day celebrations is the fireworks! Our family loves seeing fireworks, and one of the benefits of heading to Niagara Falls around the 4th of July is getting a chance to see at least two fireworks shows, if not more. Well, this year we stayed home, but still have been able to see three fireworks displays. Not only are they great entertainment, but there's some really cool science involved too.

One of my favorite websites, HowStuffWorks, explains that in order to get an idea of how the big fireworks displays work, you can learn how simple sparklers and firecrackers work. Firecrackers are black powder or flash powder (charcoal and/or aluminum, sulfur, and potassium nitrate) inside a paper tube with a fuse. Sparklers burn longer and give a bright, showery light. Sparklers consist of a fuel (charcoal and sulfur), an oxidizer (such as potassium nitrate), iron or steel powder, and a binder (sugar or starch).

Aerial fireworks are the big displays to celebrate the 4th of July and other occasions. Each is a four-part shell. The container is usually made of pasted paper and string in a cylinder shape. Inside are stars which are spheres, cubes or cylinders that are basically like sparklers. There is a bursting charge, much like a firecracker at the center of the shell; and of course, a fuse, which provides a time delay so the shell explodes at the right altitude. Each shell is launched from a mortar.  More complicated multi-break shells burst in two or three phases, and might have different colored stars, or might have explosives designed to crackle in the sky, or a whistle that explodes with the stars.
The multibreak shells have special names that sort of describe what they look like. 
Palm - has large charges or comets that travel outward, explode, and then curve down like the limbs on a palm tree
Round shell - explodes in a spherical shape
Ring shell - explodes in a symmetrical ring of stars
Willow - contains long-burning stars that fall in the shape of willow branches
Roundel - bursts into a circle of maroon shells that explode in sequence
Chrysanthemum - bursts into a spherical pattern of stars that leave a visible trail
Pistil - like the chrysanthemum, but the core is a different color than the stars
Maroon shell - explodes with a very loud bang
Serpentine - bursts to send small incendiaries in random paths, some of which may also be exploding stars
The different colors seen in fireworks displays come from the chemical compounds in the stars.
Red - strontium or lithium salts, strontium carbonate, lithium carbonate
Orange - calcium salts, calcium chloride, calcium sulfate
Yellow - sodium compounds, sodium nitrate, cryolite
Electric white - white-hot metal or barium oxide
Green - barium compounds, barium chloride
Blue - copper compounds, copper chloride
Purple - mix of strontium and copper compounds
(source: Chemistry)
We found out a few years ago (rather by accident) that if we put our old strings of Christmas lights that don't work into a fire, the compounds in the wiring produce colored flames. This is basically the same chemical principles. What do you think might be in the fire in this picture? Definitely some copper!
If you're brave enough, you can make your own sparklers, which seems like it might be a pretty neat science fair project! You can also make your own smoke bomb, similar to the kind you could buy in a fireworks store for backyard use. Both projects require some chemistry know-how, and the appropriate precautions for safety.

Now for something really neat, check out this page at the website Colossal - Art & Visual Ingenuity. It shows several long exposure fireworks photos by photographer David Johnson, like this one.
Unusual Long Exposure Firework Photographs by David Johnson long exposure light fireworks color
Source: - Photographer: David Johnson
Please visit Ben and Me: P is for Planners to join in and to see what thoughts this week's letter has prompted for other bloggers.
Blogging Through the Alphabet

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