With Bonfire Night coming up tomorrow, many of us will be looking forward to getting dressed and going outside to watch some fireworks.
Looking up at the colorful displays, it’s easy to forget that there are hundreds of years of formulation and science behind the hiss and bangs.
dr. Tom Smith, a former chemist and pyrotechnic advisor from the University of Oxford, explained to MailOnline exactly what fireworks are and how they work.
He revealed that you probably won’t see blue fireworks because the chemical that creates a blue color — copper chloride — tends to break down at high temperatures.
“The chemistry of copper flames is a fine balance,” Dr. Smith told MailOnline.
‘Small variations in the chemical species in the flame that only occur at high temperatures can cause the blue color to look pale and faint.
“So look for good blues in a display and you’ll know it’s a sign of a good manufacturer.”
You are unlikely to see a blue firecracker, as the chemical that creates a blue color – copper chloride – tends to break down at high temperatures (stock image)
The fuse will first ignite the lifting charge at the base, which quickly propels the explosive into the air, and ignite a second, internal, time-delaying fuse. When the fireworks are high in the sky, the delay fuse will have reached the gunpowder in the middle – the bursting charge – causing it to explode
What’s in fireworks?
Fireworks are said to have been invented in China in the 7th century, after the accidental discovery of gunpowder.
Most contain five components: fuel, dye, binder, pellet and the wick.
The fuel is often gunpowder, a mixture of sulfur, carbon and potassium nitrate, while the dye is usually a metal salt – a compound containing metal and non-metal atoms.
Sodium salts make yellow, strontium salts make red, barium salts make green and copper salts make blue, while mixtures generate mixtures of colors.
“If you poke a fire with a copper stick, you can see the blue color — the same kind of thing happens in a firework,” Dr Smith told MailOnline.
The dye is often combined with some charcoal and an oxidizing agent, such as nitrates, chlorates, and perchlorates, to provide oxygen for burning.
They are all held together with a special binder and coated with pea- to plum-sized granules to make ‘stars’.
The stars are bundled in a shell and can be arranged in the shape in which they will appear in the sky.
Other chemicals can be added, such as metal powders that produce sparks, or to control the reaction to prevent it from happening too quickly.
“You want the fireworks effect to linger in the sky!” said Doctor Smith.
The stars are packed in a case of gunpowder, the bursting charge, while a small portion at the base is kept separate – the lifting charge.
dr. Smith said: ‘The chemicals are either used as lifting charges – to perhaps prop up the fireworks, bursting charges to scatter the stars at the top of their flight or to produce the colored stars we are all so familiar with. to be.’
The first fuse you light is connected to the lifting charge, which initiates the explosions.
Most fireworks will contain five components: fuel, dye, binder, pellet and the wick
WHAT GIVES FIREWORKS THEIR COLORS?
Colour
Chemicals used
Red
strontium salts, lithium salts lithium carbonate, Li2CO3 = red strontium carbonate, SrCO3 = bright red
Orange
calcium salts
Gold
annealing of iron (with carbon), charcoal or lamp black
Yellow
sodium compounds sodium nitrate, NaNO3
Electric White
white-hot metal, such as magnesium or aluminum barium oxide, BaO
Vegetable
barium compounds + chlorine producer
Blue
copper compounds + chlorine producer
Purple
mixture of strontium (red) and copper (blue) compounds
Silver
burning aluminum, titanium or magnesium powder or flakes
What happens when you light the fuse?
Lighting the fuse sets off a chain reaction of processes that results in an epic play of colours.
The fuse will first ignite the lifting charge at the base, which quickly propels the explosive into the air, and ignite a second, internal, time-delaying fuse.
When the fireworks are high in the sky, the delay fuse will have reached the gunpowder in the middle – the bursting charge – causing it to explode.
The more the gunpowder is locked up, the louder the bang it will emit.
dr. Smith said, “The bursting charge illuminates the stars in the shell and also tears the casing, so that there is a wide spread of stars in the sky.”
The heat released in the combustion reaction gives energy to the electrons in the metal atoms, ‘exciting’ them to higher energy levels.
When they fall back to their original ‘ground’ energy state, they release the energy in the form of light.
The size of the gap between the ground and the excited state determines the wavelength of the light that is generated.
Different metals will have different energy gaps between their ground and excited states, leading to the emission of different colors.
dr. Smith added: “It’s important to understand that the chemicals that make up fireworks are consumed when the fireworks are fired, and the byproducts of combustion are the things that end up in the environment.
‘But the effects are quite small – we calculated, for example, that the amount of gaseous by-products from the London New Year’s Eve display is only about 1/300th of that produced by the vehicles that bring people to the display.
“Enjoy your fireworks – whether in a backyard or on a large display – and use them responsibly and safely.
“If you use fireworks, pay attention to the quality standard, read the instructions and follow them.”
Why are blue fireworks difficult to make?
The hotter the metal salt gets, the brighter the light — and therefore the color — it produces.
However, if they get too hot, the salts break down and turn pale, although some can withstand heat better than others.
While strontium chloride — which produces a red color — can withstand temperatures up to 1,500°F (816°C), the blue copper chloride begins to break down at about 1,000°F (538°C).
So pyrotechnicians are trying to add various chemicals to increase the resilience of copper chloride, but these have proven too expensive or too dangerous.
For example, arsenic once proved to be a good, blue-colored substitute, until it turned out to be highly toxic.