Page 86 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

How do fi reworks

make shapes? The chemistry behind the

spectacular patterns in the sky

odern fireworks can burst into hearts, The first shaped fireworks appeared in

smiley faces and even a representation the early 1990s to welcome returning
Mof the planet Saturn. The shape comes American troops
down to the construction of the fi rework’s shell
(container) and the arrangement of the exploding
stars (pyrotechnic pellets) within them. As aerial
shells are often spherical, they tend to explode
symmetrically. Arranging the stars into the
desired shape on a piece of card within the shell
makes them explode outwards in that pattern.
Manufacturers also use multi-break shells that
have different compartments inside them, often
with stars of various colours and compositions.
When these are placed and fused in a specifi c
order, they will explode in sequence to create
recognisable patterns and shapes in the sky.
However, it’s not an exact science; many displays
will fire several copies of the same firework at the

same time so that at least one of them creates the
desired shape in the audience’s line of sight.
Inside a fi rework
Sparkler science
See how the internal design affects
The chemical composition of sparklers the shape of the explosion Burst charge
consists of three important components: an This central structure
oxidiser, a binder and a metal fuel. These produces a large, quick
three substances are bound together in a explosion that sets the
paste, which is then coated onto the iron Fuse entire compartment off.
wire that forms the sparkler’s main body. This initial fuse ignites
A powdered metal is essential, as it helps other, smaller fuses within

produce sparks that generate the famous the firework. In public
glittery effect and can also colour the displays, these are lit by
electrical contacts called
sparkler. Aluminium, titanium and wirebridge fuseheads.
magnesium all produce bright, white sparks,
whereas iron will burn with a characteristic
orange hue. When iron and titanium are
combined they form an alloy called Gunpowder
ferrotitanium, which produces golden yellow Also known as black
sparks when it burns. powder, this provides
For even more colours, salts of various the explosive force
metals can be added to sparklers, which is that ignites the stars
often the technique used for creating Timed fuse and launches them in

coloured fireworks. Copper salts produce This section ignites all directions.
green-blue, barium salts create green and the burst charge once
strontium salts produce red. the fi rework has
reached the
appropriate altitude.

Titanium Iron
Lifting charge
The initial explosion sends
the shell soaring into the air
Aluminium & Magnesium Ferrotitanium without detonating the main Star arrangement
compartment. Different chemicals are added to create
Powdered metals react with oxygen to produce a range of colours, while the shape is © Thinkstock
metal oxides, which burn with specific colours determined by the arrangement of
small, combustible pellets.

86 How It Works