Fireworks become a July 4 tradition
July 3, 1776 future president John Adams wrote to his wife about a great Anniversary Festival celebrated with guns, bonfires and illuminations (fireworks) It was a natural idea. By the 1700s Europeans used them at celebrations. King George III had fireworks on his birthday. July 4, 1777, defiant Americans celebrated Independence Day with their own noisy fun. In Philadelphia ships fired cannons. People fired guns. In a field near Independence Hall folks set off fireworks. People in other cities did, too. In the 1800s European immigrants included fireworks experts who added even more bang and boom to national birthday parties.
Scientific flash behind fireworks
Most pyrotechnics are designed not to explode. Fireworks at their flashiest are cooling down. Rocket's red glare, bombs bursting in air, are pyrotechnics refined ever since China first used black powder for noisy fireworks to scare away evil spirits. Ingredients in black powder and all fireworks are what they always were: fuel, providing heat, and oxidizer providing more oxygen than ambient air can supply, to accelerate reaction and burning. Slower reactions make good visual effects. Pyrotechnic chemists creating dazzle instead of bang don't want their work to explode, but to burn and give a good visual show. For desired effects each ingredient's particle size must be just right and ingredients blended just right. For slower burning, chemists use grains 250 - 300 microns (size of a small grain of sand) and don't blend ingredients well. That makes it harder for fuel and oxidizer to combine and burn, producing longer, brighter effects. Really sparkly fireworks use 1,000 micron grains ignited by black powder fire around them, combined with air to burn with a spark effect. Example fuel/oxidizer/sparkle combination: sparklers, made of medium-sized grains of fuel and oxidizer to get the fire going, mixed with even bigger aluminum grains. Ignited those grains burn using oxygen in the air, giving off sparks. Aluminum burning at 2,700 degrees F (1,500 degrees C) produces golden sparklers. At 5,400 degrees F (3,000 degrees C) aluminum produces white sparks.
Other chemicals produce colors using thermodynamics' first law: nature conserves energy. Energy is never lost, but transferred elsewhere. Energy from fire in basic fuel transfers to colorant chemical atoms, exciting them to a higher energy state. Electrons literally orbit farther from the atom's nucleus. Cooling they move back to a lower state of energy. As electrons calm down their energy converts to radiation, fireworks' light. You see fireworks colors as they cool. Their signature chemicals each emit light at a specific wavelength, producing a specific color: strontium = red, copper = blue, barium = green, sodium = yellow/orange. Like combining crayon colors, combining color chemicals gives additional colors. Strontium (red) + copper (blue) = purple. Chemists use color chemical pellets as big as sugar cubes mixing colorant and fuel to the right degree and with the right-size particles so pellets burn at the desired rate. Technicians calculate how high to shoot the shells so they burn before landing.
Designers give fireworks shape and sound. Whistling: fuel in cardboard tubes open on one end burn inside the tube. CO2 rushes whistling out the open end. Shapes of exploding lights depend on how fuel and colorants are packed. If the explosive charge is in the middle, surrounded by sodium pellets, the timer fuse ignites the sodium and shoots it out in that familiar yellow/orange circle. Two rows of color pellets around a central bomb gives a double ring. If the shell's inside is an interspersed mix of fuel and color the explosion ignites the colorant to spread and shower as a glowing willow tree. For tricky shapes like stars or hearts color pellets are pasted on paper in the desired pattern and put in the middle of the shell with explosive charges above and below it. Charges going off burn the paper, sending ignited color pellets out in the pattern they were in on the paper, spreading wider apart as they fly.
Fireworks get charge from tiny electrons
Miniscule building block of atom gives artists paint to create festive 4th
The excitement of a huge fireworks display starts with the excitement of the tiny part of the itsy-bitsy atom: the electron. Without excited electrons there are no blazing reds and brilliant blues, no ear-splitting bangs. Electrons goosed by exploding gunpowder and desperate to return to their usual state release excess energy by emitting light. 100 years ago scientists figured out how atoms are structured by studying the wavelengths of the light, the colors, given off by fireworks and other burning metals. Now, as communities get ready to light their skies July 4, science still finds new twists in the ancient Chinese art of fireworks.
A California company will introduce high-tech pyrotechnics at the Macy's fireworks display in New York. Music and fireworks are now digital, fusing ancient art with modern technology. Each shell contains a computer chip that coordinates the burst of color and sound within 1/1,000 of a second to the famous opening of German composer Richard Strauss' "Also Sprach Zarathustra," the theme from "2001: A Space Odyssey."
Installing a computer chip in a shell triples the cost, but it's worth it for big displays. The chip-in-a-shell will revolutionize the industry. Fireworks are not rocket science, because they don't use rockets. Instead, fireworks are shot out of fiberglass guns. Some do have rocket motors in them to make them squirm around in the sky. A fireworks show is 20% science, 80% artistry. Chemists make paint and artists create pictures.
Fireworks are mostly chemistry in action at the subatomic level in superheated metals. Using recipes handed down for generations, fireworks-makers use different metals each of which produces a different color, mashed, baked into paste and dried into 2' x 2' cakes, cut into pieces the size of sugar cubes with something akin to a bread knife and coated with gunpowder to help them explode. These cubes, called stars, are then dried for a week. Hundreds if not thousands of these stars are packed with more gunpowder into shells that can be as big as a foot in diameter. The shells are fired into the air, where they explode, where in millionths of a second the action takes place. The gunpowder explodes, producing temperatures as high as 2,700 degrees, transfering energy into the atoms, especially the electrons (the negatively charged particles orbiting the atom's center, changing their paths. The electrons are supercharged with electricity. Nature dictates that they prefer to return to their usual, more leisurely state. To rid themselves of that excess energy the excited electrons must release heat or light. Metals used in fireworks emit light, providing brilliant colors.
The fireworks rainbow has 5 primary colors: red, white, blue, green and gold. Fireworks makers use sodium to produce yellow or gold, barium for green, strontium for red and magnesium for white. Blue, the toughest color to make, is the rarest. It's created from copper arsenic, a dangerous chemical. For smiley faces, Saturn rings, hearts and other trendy designer bursts, fireworks-makers arrange the stars and gunpowder in specific patterns. They say they continue to find new chemicals and techniques to improve their ancient art. As with anything, the sky is always the limit.
Color by Fire
Early fireworks were enjoyed more for sound than show. In its simplest forms gunpowder explodes quickly, leaving a terrific bang but not much to see besides a rather brief golden glow. Over time people discovered that using chemical compounds with greater amounts of oxygen made the explosives burn brighter and longer. Multi-hued displays we know now began in the 1830s when Italians added trace amounts of metals that burn at high temperatures, creating beautiful colors. Other additives also produced interesting effects. For example, calcium deepens colors, titanium makes sparks, and zinc creates smoke clouds.
Oriental shells burst into a spectacular, spreading chrysanthemum shape that takes up the whole sky. The random pattern of color produced by American shells is easily distinguished from this symmetrical pattern and by the longer duration of their colors. Modern electronics now permit precise firing of fireworks; choreographing bursting fireworks with music; and hearts, stars, and other geometric patterns.
For hundreds of years, even before Francis Scott Key wrote of seeing "the rockets' red glare, the bombs bursting in air," people were awed by fireworks' bright lights and big noise. Ancient China used fireworks at festivities and to frighten enemies in battle. Captain John Smith set them off in Jamestown in 1608, enjoying a bit of English popular entertainment and impressing Native Americans.
Smoky Origins
Legend has it China made the first fireworks in the 800s, filling bamboo shoots with gunpowder and exploding them at the New Year hoping the sound would scare away evil spirits. According to tradition, Marco Polo brought this technology back to Europe. Fireworks' origins are shrouded in smoke. The China story is widespread and possibly true but fireworks may in fact have developed in India or Arabia. Fireworks became known in Europe during the 1300s, probably after returning Crusaders brought them from the East. By the 1400s Florence, Italy, was the center of fireworks manufacturing. At this time fireworks were just one effect in a celebration rather than its focus. At Italian religious festivals plaster figures spewed fireworks from their eyes and mouths. The 1533 coronation parade for Anne Boleyn included a papier-mache dragon that belched fire. 1700s displays became more elaborate and were popular with European royalty. French king Louis XV ordered extravagant displays of fireworks at Versailles, and Russian czar Peter the Great put on a five-hour show after the birth of his son. Meanwhile American colonists used fireworks to mark happy occasions. Today fireworks are a key part of Independence Day in the United States, Guy Fawkes' Day in the United Kingdom, Bastille Day in France, and New Year's Eve worldwide.