The First Firecrackers
The history of fireworks goes back thousands of years to China during the Han dynasty (~200 B.C.), even long before gunpowder was invented. It is believed that the first "firecrackers" were likely chunks of green bamboo, which someone may have thrown onto a fire when dry fuel ran short. The rods sizzled and blackened, and after a while, unexpectedly exploded. Bamboo grows so fast that pockets of air and sap get trapped inside of the plant's segments. When heated, the air inside of the hollow reeds expands, and eventually bursts through the side with a long bam!
The strange sound, which had never been heard before, frightened people and animals terribly. The Chinese figured that if it scared living creatures so much, it would probably scare away spirits - particularly an evil spirit called Nian, who they believed to eat crops and people. After that, it became customary for them to throw green bamboo onto a fire during the Lunar New Year in order to scare Nian and other spirits far way, thus ensuring happiness and prosperity to their people for the remainder of the year. Soon, the Chinese were using bursting bamboo for other special occasions, such as weddings, coronations, and births. The "bursting bamboo", or pao chuk as the Chinese called it, continued to be used for the next thousand or so years.
Discovery of Gunpowder
Most historians believe that gunpowder was first discovered sometime during the Sui and Tang dynasties (~600-900 A.D.) in China. It was most likely discovered accidentally by alchemists who were experimenting with sulfurous mixtures in an attempt to create an elixir of life. During this period of chemical discovery and experimentation, the alchemists kept records of certain poisonous and dangerous compositions that should never be mixed - including one particular mixture consisting of sulfur, saltpeter (potassium nitrate), honey, and arsenic disulfide. The texts make reference to such a mixture igniting accidentally while being cooked over a fire, resulting in a large, bright, hot flame that burned the hands and faces of the alchemists tending to it, and even burnt down the shack there were cooking it in! Despite the warnings, some alchemists were intrigued by the mixture, and continued experimenting with it to try to find ways to make it more powerful. Their crude mixtures weren't as powerful as modern gunpowder because it didn't contain as much potassium nitrate, but nevertheless burned very hot and bright. It was named huo yao, or the "fire chemical". It was soon discovered out that if the "fire chemical" was put inside of bamboo tubes and thrown in the fire to be ignited, the gases produced by the burning powder would blast the tube apart with a much louder and more powerful bang than just green bamboo. The firecracker was born.
Over time, chemists discovered that the key to the vigorous burning of gunpowder was the fact that saltpeter was rich in oxygen, which it released as it burned. They soon figured out how adding more saltpeter to the mixture made it burn faster, thus making it a more powerful explosive and louder when used in firecrackers. The Chinese were well aware of the killing power of these explosive devices, and by the 10th century, began using them for military purposes. The Chinese used their gunpowder to create a variety of explosives, including bombs and "fire arrows" - bamboo firecrackers attached to regular arrows and shot at the enemy. The original idea behind the Chinese bombs was to scare the enemy into fleeing by creating terrifying, earth-rattling explosions and lightning-like flashes. Eventually the aim shifted from scaring the enemy to simply blowing them up. Around the 11th century, the proportion of saltpeter in gunpowder was raised to about 75% of the total mixture, along with about 5% charcoal and 10% sulfur (that same formula is still used today, nearly 1000 years later!).
Soon after that, firecrackers began to change. Rather than using bulky bamboo stems, firecracker makers began filling stiff paper tubes with gunpowder and inserting fuses made from tissue paper with a trail of gunpowder inside. A variation of a firecracker, called a ground rat, was created around 1200 A.D. It consisted of a paper firecracker that was open on one end. Instead of exploding, the burning gas inside shot out of the opening and propelled the rat randomly around the ground. Rats were quickly adapted for use by the Chinese military because of their psychological effect on the enemy - scaring soldiers and causing horses to go wild. Occasionally the rats would fly into the air momentarily, which gave the military designers the idea of putting guidance fins on the rats to straighten their flight path. This led to the creation of the first rockets. Civilian firework makers took the military's rocket design and modified it to include an explosive charge, which were then fired into the air - marking the first use of aerial fireworks.
