If you have ever been to an aerial fireworks show at an
amusement park, baseball game, Fourth of July celebration or
on New Year's Eve, then you know that fireworks have a special
and beautiful magic all their own -- a good show is absolutely
Click on this image to
see a short fireworks display (1.5
Have you ever wondered how this magic works? What is
launched into the sky to make these beautiful displays? In
this edition of HowStuffWorks,
you will learn all about aerial fireworks.
Just about everyone in the
United States has some personal experience with fireworks,
either from Fourth of July or New Year's Eve celebrations. For
example, you have probably seen both sparklers and
firecrackers. It turns out that if you understand these two
pyrotechnic devices, then you are well on your way to
understanding aerial fireworks! The sparkler demonstrates how
to get bright, sparkling light from a firework, and the
firecracker shows how to create an explosion.
Firecrackers have been around for hundreds of years.
They consist of either black powder (also known as
gunpowder) or flash powder in a tight paper tube with a
fuse to light the powder. Black powder, discussed briefly in
Engines Work, contains charcoal, sulfur and potassium
nitrate. A composition used in a firecracker might have
aluminum instead of or in addition to charcoal in order to
brighten the explosion. To find out more about flash powder,
which was originally used in photography, click
Sparklers are very different from firecrackers. A
sparkler burns over a long period of time (up to a minute) and
produces extremely bright and showery light. Sparklers are
often referred to as "snowball sparklers" because of the ball
of sparks that surrounds the burning portion of the sparkler.
If you look at Patent
#3,862,865: Sparkler composition, you can see that a
sparkler consists of several different compounds:
- A fuel
- An oxidizer
- Iron or steel powder
- A binder
Question of the Day for a discussion of oxidizers --
potassium nitrate is a very common one. The fuel is
charcoal and sulfur, as in black powder. The binder can
be sugar or starch. Mixed with water, these chemicals form a
slurry that can be coated on a wire (by dipping) or poured
into a tube. Once it dries, you have a sparkler. When you
light it, the sparkler burns from one end to the other (like a
The fuel and oxidizer are proportioned, along with the other
chemicals, so that the sparkler burns slowly rather than
exploding like a firecracker.
It is very common for fireworks to contain aluminum, iron, steel,
zinc or magnesium dust in order to create bright, shimmering
sparks. The metal flakes heat up until they are incandescent
and shine brightly or, at a high enough temperature, actually
burn. A variety of chemicals can be added to create colors.
page for a good explanation of the chemistry and physics
of color in fireworks.
An aerial firework is
normally formed as a shell that consists of four parts:
- Container - Usually pasted paper and string
formed into a cylinder
- Stars - Spheres, cubes or cylinders of a
- Bursting charge - Firecracker-like charge at the
center of the shell
- Fuse - Provides a time delay so the shell
explodes at the right altitude
These are small shells, about the size of a
peach, that you can buy at roadside stands in some
states. The sphere is the shell, and the small cylinder
below is the lifting charge that shoots it out of the
launch tube. The green fuse lights the lifting charge,
which in turn lights the shell's fuse. Shells that you
see at a show are typically the size of a cantaloupe or
The shell is launched from a mortar. The
mortar might be a short, steel pipe with a lifting charge of
black powder that explodes in the pipe to launch the shell.
When the bursting charge fires to launch the shell, it lights
the shell's fuse. The shell's fuse burns while the shell rises
to its correct altitude, and then ignites the contents of the
shell so it explodes.
A simple shell used in an aerial fireworks
display. The blue balls are the stars, and the gray is
black powder. The powder is packed into the center tube,
which is the bursting charge. It is also sprinkled
between the stars to help ignite them.
Simple shells consist of a paper tube filled with stars and
black powder. Stars come in all shapes and sizes (several of
the links below list dozens of recipes for different types of
stars), but you can imagine a simple star as something like
sparkler compound formed into a ball the size of a pea or a
dime. The stars are poured into the tube and then surrounded
by black powder. When the fuse burns into the shell, it
ignites the black powder, causing the shell to explode. The
explosion ignites the outside of the stars, which begin to
burn with bright showers of sparks. Since the explosion throws
the stars in all directions, you get the huge sphere of
sparkling light that is so familiar at fireworks displays.
More complicated shells
burst in two or three phases. Shells like this are called
multibreak shells. They may contain stars of different
colors and compositions to create softer or brighter light,
more or less sparks, etc. Some shells contain explosives
designed to crackle in the sky, or whistles that explode
outward with the stars.
Multibreak shells may consist of a shell filled with other
shells, or they may have multiple sections without using
additional shells. The sections of a multibreak shell are
ignited by different fuses. The bursting of one section
ignites the next. The shells must be assembled in such a way
that each section explodes in sequence to produce a distinct
separate effect. The explosives that break the sections apart
are called break charges.
The pattern that an aerial shell paints in the sky
depends on the arrangement of star pellets inside the shell.
For example, if the pellets are equally spaced in a circle,
with black powder inside the circle, you will see an aerial
display of smaller star explosions equally spaced in a circle.
To create a specific figure in the sky, you create an outline
of the figure in star pellets, surround them as a group with a
layer of break charge to separate them simultaneously from the
rest of the contents of the shell, and place explosive charges
inside those pellets to blow them outward into a large figure.
Each charge has to be ignited at exactly the right time or the
whole thing is spoiled.
To see how some common
multibreak shells look in the sky, try the quick and easy
"HowStuffWorks Field Guide to Aerial Fireworks." It's
interactive, so you can click on a name and see the fireworks
display that goes with it. The next time you witness a big
fireworks show, you will know the names for each type of shell
You can see how some of the more common multibreak shells
look in the sky by clicking on the buttons in the illustration
above. You can read descriptions of these shells below:
For more information on fireworks and related topics, check
out the links on the next page.