Fourth of July celebrations are never complete without fireworks. Since we were kids, we've enjoyed the wonder and magic of fireworks. We've wondered where it all came from, how it all got started and what's in fireworks.

There is an old fable about a Chinese cook who accidentally mixed the three common kitchen ingredients - saltpeter or potassium nitrate, sulfur and charcoal and lighted it. It produced colorful flames as well as making a huge explosion when enclosed in a bamboo shoot. This discovery led to the invention of sparklers and firecrackers. There is evidence that the Chinese used fireworks for entertainment as well as to cast away evil spirits since 206 BCE - AD 220. But the Chinese discovery of fireworks is just one side of fireworks story.

Fireworks were also thought to have originated in India. There are references in ancient Hindu literature to smoke balls suggesting the knowledge of gunpowder. In the famous Ramayana myth Vishwamitra uses a weapon called the shikhara - which led historians to conclude that the ancient Hindus were acquainted with gunpowder. It would not be surprising as the ancients share the silk route for trading. The same trade route used by Marco Polo and the Arab traders which transported fireworks into the west.

Fireworks were used as fuel to power rockets that had arrows in them. In the 6^th century the Chinese would use these rocket arrows against the Mongol invaders. The principle behind these rocket-arrows is still used today when we see the fireworks.

Back in those days black powder wasn't easily available so nitre-beds had to be prepared by mixing manure with either mortar or wood ashes. Common earth and organic materials like straw to allow air to circulate inside. A typical pile is about 1.5 by 2 meters wide and 5 meters long. The whole pile is covered from the rain and kept moist with urine. (Ok can it get any gross?) It was often turned to accelerate decomposition and leached with water after a year. After all that, the liquid that contained the various nitrates was converted with wood ashes to potassium nitrates, crystallized and refined for use in gunpowder. In England this privilege of making gunpowder and explosives was a monopoly of the family of John Evelyn since before 1588!

Today the scene is different. Potassium nitrate comes from deposits of sodium nitrate in the Chilean deserts. The sodium nitrate is purified and then reacted with potassium chloride where the less-soluble potassium nitrate is precipitated out. Now, that sounds much better doesn't it?

Sulfur is used in fireworks because of its flammable nature. There are two ways to get sulfur - the Sicilian process, which was first used in Sicily and the Frasch process. In the Sicilian process, the sulfur from rocks present in volcanic regions are extracted. First the sulfur deposits are piled and stacked in brick kilns built on sloping hillsides with airspaces between them. The powdered sulfur is then put on top of the sulfur deposit and lit on fire. It produces heat as the sulfur burns and melts the sulfur deposits, causing the molten sulfur to flow down the sloping hillsides. The molten sulfur can be then collected in wooden buckets. They then purify the sulfur through distillation.

Frashch process is a more scientific process where three concentric pipes are used. Outermost pipe contains superheated water which melts the sulfur and the innermost pipe is filled with hot compressed air which makes foam and pressure. The resulting sulfur foam comes out of the middle pipe. This process produces sulfur with 99.5% content purity.

The Fourth of July celebrations in America had fireworks since 1777! That's before the American Revolutionary War was won from the British. Each year retailers across the nation get a surge in fireworks sales. Although fireworks in your back yard might be fun we can never miss out the public displays of fireworks like Macy's Fourth of July Fireworks in New York or the other fireworks in cities like St. Lousis, Washington, DC, Boston, and Philadelphia. Every Fourth of July, we become kids again with BBQs, hot dogs and fireworks make it a nice complete summer evening.

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