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Why do fireworks burn different colours? How do they work? Explanation and a brief history.

Updated on February 15, 2014

When were fireworks invented and by who?

Fireworks have been around for centuries. The birthplace is believed to be China, where the first explosives, being in the form of black powder, were made during the Sung dynasty (960-1279). Documents have been found showing how to wrap this black powder in paper to make a 'fire pill'. It goes on to describe how the loud bang was used to scare off evil spirits.

It was found that storing sulfur, saltpeter and charcoal would explode because of how easily flamable it all was. Initially it was used for entertainment purposes in small quanitities but it was soon used in a military applications - rocket fuel, with carved wooden rockets in the shape of dragons. These rockets shot powered arrows from their mouths to great effect against the Mongols, who tried to invade Chinese boarders.

The knowledge of rockets spread west during the seventh century. The Mongols are credited with taking the rockets (the Arabs called them Chinese arrows) to Europe around 1241. However they were still very much just used to power arrows so it was just an explosion.

With Europe being shown this new technology it wasn't long before they adapted it. During the 14th century the gun was invented using gunpowder. This started a new trade in Europe for the military called firemakers, who made guns but also started to experiment with combinations of metallic salts to make brilliant colours when they burnt. Each different metal salt produced a different colour it was found out. This was the birth of the modern firework and was used for celebrations and victories.

During the Renaissance, Italy emerged as the leader behind elaborate fireworks but Germany lead the way in scientific advancement. During the mid 17th century though, fireworks were being used significantly over the whole of Europe. Injuries associated with their use though soon lead to a decline in activity.

Today, fireworks (with alot better health and safety knowledge) are used throughout the world however, technology has not moved on much since then when it comes to rockets and gunpowder. The same principles behind these first rockets are still used today.

How a firework is made up:

How do fireworks work!

There is no denying that fireworks are amazing. There is no surprise that fireworks are used for a whole number of celebrations from a football game to New Year's Eve.

Many people buy fireworks and do their own display too. But have you ever wondered how they actually work?

As explained above, the technology hasn't changed much over the centuries. But there are differnet types we use: firecrackers, sparklers and aerial fireworks. All different in the way they use this technolody:

  1. The first use of this technology was the firecracker (which is still used today) but they are basically rolled paper tubes filled with black powder and a fuse. When the fuse is lit, the fire burns burns until it reaches the powder and then it explodes.
  2. Sparklers burn brightly for a long time and do not explode. They contain more substances than a firecracker to allow them to do this. The bright light and sparks are produced from burning metals such as aluminium, iron, steel, zinc or magnesium.
  3. Aerial fireworks are even more complicated, often made up of four parts. They need a container, usually made of card so it can burn easily, a fuse, a bursting charge made of black powder (like a firecracker) and stars. It basically works like a firecracker in the first three parts but for the stars, which are sparkler like substances shaped into small spheres. They are mixed throughout the interior of the shell and these produce the bright colours you see when the firework explodes.

Aerial fireworks are usually launched into the sky from short pipes filled with a lifting charge of black powder. This ignites the shell's fuse, which burns as the shell rises and when it hits the bursting charge the shell explodes and the stars ignite, fly in all directions and produce the wonderful colours and patterns you see in the sky.

But you can have fireworks that go off in different stages!

Fireworks have developed to allow explosions over time. The firework explodes in different stages allowing different effects to be generated. These special fireworks have multibreak shells. This basically means shells within shells that explode in different phases so that the stars within each shell ignite at different times.

Why do fireworks look different then?

Fireworks can explode in circles, or they can shower down towards Earth. This all depends on the way the stars are arranged in the shell. To create a specific pattern, manufacturers create an outline of the pattern they want with the stars. They then surround these stars with a special charge that will seperate them in a direction they wanted when the shell explodes.

What makes fireworks burn different colours?

Metal salts produce different colour flames when they are burnt. The colours produced when the firework explodes are created using this knowledge.

The stars inside the shell of the firework are a careful mix of the right chemical compounds.

These compounds are produced by an elemental metal salt, sulfur and charcoal. When ignited they burn the colour of the metal salt as indicated in the table below:

Firework colour
Metal that creates it
Example of a salt that is burnt to create it in fireworks
Red
Strontium
Strontium Carbonate
Orange
Calcium
Calcium Chloride
Yellow
Sodium
Sodium Nitrate
Green
Copper
Copper Chloride
Purple
Potasium
Potasium Chloride
Blue
Zinc
Zinc Chloride
White
Magnesium
Magnesium powder works best instead of a salt

Of course, what manufactorers do is mix these salts to produce a certain colour for the flame they want. It is a very dilicate science which produces some very effective results.

Fireworks: another way in which science has made the world a better place.

I remember doing this experiment at school as well as spraying metal salts, dissolved in ethanol, into a bunson burner. It was one of my favourite experiments due to the great colours we made.

We had a group of us and we all sprayed a different solution into the flames at once to see what sort of colours we could produce. I was amazed to learn at the time that this is the same science we used to make fireworks.

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