How Fireworks Work

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I can't even count how many people have told me stories of how they loaded a shell into the mortar incorrectly, only to have 

On this page you'll learn about how all of the different types of consumer fireworks work.  Unlike the other sections, this page lists the fireworks in order of complexity - the most basic types of fireworks will be listed first, followed by the more complex ones.

Warning:  the cutaway diagrams shown below are for educational purposes only.  They should not be used as a guide for constructing your own fireworks.  Never attempt to take apart fireworks.

AERIAL/CAKE

Repeating aerials are just as complex as aerial shells because that's basically what a repeater is - many tubes of mini-"shells" all in one unit.  These clusters of tubes each have a clay plug in the bottom and a black powder lift charge.  There are two holes in the side of each tube, and as the device is being constructed, small chunks of fuse are used to connect each tube to its neighbor.  This way, when the first lift charge ignites and sends the effect into the air, the tube next to it ignites shortly afterwards, and so on.  Most devices have several parallel-fused tubes towards the end of the "fire trail", so that several tubes ignite simultaneously (or in very rapid succession) at the end of the performance in order to intensify the display.

Repeaters contain smaller "effect tubes" that are usually about one-third to half the length of the main "launching tubes".  Each of these has a construction very similar to a shell.  When the lift charge in the launching tube fires, it ignites a time fuse and (usually) a colored star composition in the bottom of the effect tube.  The star composition burns brightly as the tube rises, and at the at its maximum altitude, the burst charge ignites the effects.  The diagram at the right shows stars, which would look like a small, uneven shell burst when ignited.  But if you have ever lit off a repeater before, you would know that there are dozens of possible effects: effects tubes that go up and explode, ones that whistle, ones that crackle, ones that spin around on the way up, and even ones that give off parachutes.  Next time you light a repeater, come back to that area the next morning and look at the ground around where you set it off - you will see dozens of these spent effects tubes (with nothing but the clay plug left).

AERIAL SHELLS

Aerial shells are one of the most beautiful and certainly one of the most complex types of fireworks.  A shell consists of main parts: a container, a lift charge, a time fuse, a burst charge, and stars/effects.  The container, or shell casing, is a strong wall that protects the contents.  The lift charge propels the shell out of the tube, and the time fuse ignites the burst charge at the right altitude.  The burst charge then ignites the effects.

Shells are launched from a tube known as a mortar.  A string loop is often attached to consumer firework shells so it can lowered into the mortar by the fuse.  When the fuse enters the shell, it ignites the burst charge, creating an explosion that ignites the time fuse and shoots the shell high into the air.

As the shell ascends, the time fuse burns towards the burst charge.  At the precise altitude - usually where the shell is briefly hanging in the air - the time fuse ignites the black powder burst charge, causing the shell to explode.  The powerful explosion blasts apart the shell casing and ignites the stars, scattering them in all directions across the sky.  These stars burn brightly and give off sparks, creating a huge spherical pattern in the sky.


DISPLAY TUBES

Repeating aerial tube devices are little more than several aerial shells fused together to go off in sequence, with a few seconds of delay between each shell.  There are usually anywhere from 3 to 7 tubes which are glued down to a thick wooden base to stabilize the device.  Each tube contains a typical aerial shell in the bottom, protected by a cardboard disk and a cap at the top of the tube.  Holes are drilled in the bottom of each tube, and small chunks of fuse connect each shell to the tube adjacent to it.  The tube on the end has a long fuse that runs outside for a few inches.  

When that fuse is lit, the first shell fires.  The lift charge of that shell ignites the chunk of fuse leading into the next tube, which in turn ignites a shell about four seconds later, and so on.


FIRECRACKERS 

Firecrackers are the simplest and oldest of fireworks.  A single firecracker is simply a paper tube of several layers to give it strength.  It is plugged at both ends with a dry clay-like substance, and contains a small amount of flash powder in the middle.  When the fire from the fuse ignites the flash powder, it creates a large volume of hot gas in a short period of time.  The casing of the tube contains this gas until the pressure blasts the tube open with a loud "crack"


FLYING SPINNERS (HELICOPTERS)

Flying spinners are another one of the most popular fireworks.  It is little more than a ground spinner with a paper or plastic wing unit attached to the tube.  When the propellant composition is ignited, it creates thrust which spins the device around.  But whereas a ground spinner would simply bump around on the ground, the spinning motion of a flying spinner causes the angled wings to direct airflow downward, lifting the device into the air exactly like a helicopter (hence the name).

Helicopters have a burst charge at the end of the propellant compound, which explodes at the end of the device's flight and ejects stars, ladyfingers, or a parachute.


FOUNTAINS

Single tube fountains consist of a cardboard tube (which may be inside of a cone) that stands vertically on a plastic base.  The tube is charged with a composition designed to make lots of sparks, flame, and gas.  At the end of the tube there is a clay plug with a hole drilled into it, forming what is known as a "choke".  Without a choke, the fountain would only give off a weak spray of sparks.  With a choke, however, a lot of pressure builds up inside of the tube, which forces the gas and sparks out of the fountain with a much greater velocity.  Very small fountain tubes (i.e., 1/4 in diameter) don't require chokes.

The fountain composition is often layered as to produce different effects at different stages in the burning.  For instance, one layer may burn to produce orange sparks, followed by a layer that produces white sparks and green star fragments.

 


GROUND SPINNERS

Single tube ground spinners consist of a single tube (imagine that!) that is plugged at both ends with clay and is filled with a rapidly-burning composition.  A small fuse hole has been drilled into the side of the tube, near one of the ends.  When the fuse ignites the composition, hot gases are produced and rush out of the hole, propelling the device around its central axis.  Because it is off-balance and doesn't have quite enough thrust to fly, the firework spins wildly and randomly on the ground.  The characteristic blossom shape of Ground Bloom Flowers is caused by the tube rapidly bumping up and down as it spins.

MINES 

Mines are basically a ground-level aerial shell burst that is directed upwards.  The bottom of the tube contains a black powder lift charge, similar to that found in a shell.  When ignited, the lift charge engulfs the stars in flame, igniting them as it propels them out of the tube in a V-shaped pattern.  The "spread" of the stars in the sky depends on both the length and the width of the mortar.  

Consumer mines are typically one-shot-per-tube devices that are bunched together, resembling repeaters.  Professional mines, however, are reloadable - the lift powder and stars are put in bags, which are lowered into the mortars and ignited.


NOVELTIES 

There are hundreds of different novelties, and they all work more or less the same way.  The example I've chosen to illustrate here is the ever-popular tank.

Tanks contain several tiny fountains that shoot multi-colored stars and often produce just enough thrust to move the device along if it's placed on a hard, level face.  A small length of gray tissue firecracker-type fuse transfers the fire from the rear fountain to the front "guns" of the tank.  These small fountains are only filled half way with composition, so the fuse can therefore enter from the side in order to ignite it.


PARACHUTES

Aerial parachutes have a complex internal construction very similar to that of an aerial shell.  Parachutes can come in the form of single tubes with a base, or clusters of tubes that look like a tall repeater.  The launch tube is usually quite thick to withstand the forces of the powerful, noisy lift charge. When the lift charge ignites, it blasts a "parachute tube" high into the air.  Meanwhile, a time fuse is burning inside of the parachute tube, which in turn ignites a tiny burst charge when the tube reaches the highest point in its flight.

 Much like a model rocket, this burst (or "ejection") charge blasts the parachutes from the parachute tube.  There is often a small piece of paper "wadding" between the burst charge and the parachutes to prevent the chutes from burning up.  The tissue parachutes are attached to small chunks of tube filled with clay to serve as weights.  They can be packed together tightly, which enables several parachutes to be put inside of one parachute tube.

Sometimes the weight tube is filled with a smoke composition.  A short piece of fuse transfers fire from the parachute tube's burst charge to the composition in the weight, which smokes as it drifts down from the sky.  Nighttime parachutes use a steady-burning star or strobe composition in place of smoke composition.


REPEATING FOUNTAINS

Repeating fountains are large tubes that contain many single fountains that are fused to ignite sequentially.  Because of this, repeating fountains last much longer and usually have a wider variety of effects than single-tube fountains.  

Each of the individual fountain tubes has a hole near the bottom with a fuse coming out of it, which leads up to the top of the next tube.  This fuse ignites when the tube has almost finished burning, and by the time it does, the next tube has already ignited.  This sequence continues for the remainder of the tubes.  Sometimes a fuse will lead to several tubes, igniting them all at once to produce an intense spray of noise and color as a sort of 'finale'.

Click here to see an actual picture of the fusing of a repeating fountain.


ROCKETS & MISSILES

Rockets are the second oldest type of firework that were originally discovered by mistake - the Chinese discovered that an open-ended firecracker propelled itself along the ground, rather than exploding.  Since then, their construction has become much more complex.  Rockets and missiles operate the same way; the only difference being in the method of stabilization (either fins or a stick).  When the burning fuse enters the end, the cone-shaped chamber ignites within a fraction of a second.  The shape of this chamber provides a very large surface area for burning to take place, creating a large volume of gas which is forced out of the back to create thrust.  As a result, the rocket/missile travels in the opposite direction.  Because of the rapid burning, the fuel is exhausted in a matter of seconds.  The casing of the rocket is usually fairly thick so it can withstand the high pressures of the burning fuel.  The internal time fuse then transmits fire to the burst charge, which explodes to break open the rocket casing and ignite the stars or reports inside.


ROMAN CANDLES

Though roman candles seem like a simple firework, the construction process is quite complex and difficult.  After a clay plug at the bottom, the roman candle tube consists of alternating layers of lift charge, stars, and delay compositions.  When the fuse enters the tube, it activates a slow-burning delay composition that makes its way down.  Within seconds, the delay charge reaches the first star, simultaneously igniting both it and the lift charge below it, which blows the star out of the tube.  This ignites another layer of delay composition, which will light a star and the lift charge to blow it out a few seconds later.  This continues until every star has been blown out of the tube.  


 

SMOKE DEVICES

The most famous consumer smoke device is probably the "smoke ball" or "smoke bomb", a large ball of clay with a hollow center.  Inside the center is a composition that usually consists of potassium chlorate, lactose, and a powdered dye.  When ignited, this composition burns at a relatively low temperature, which evaporates the dye into fine particles and disperses them into the air (so the colored "smoke" isn't actually smoke at all).  

The smoke composition must be "cooled off" fairly quickly after ignition, or else the dye particles will react with oxygen to burn up.  This is why smoke is always observed rapidly exiting the burning chamber.  If you hold a smoke device too close to a solid object, the burning particles can't get away fast enough to cool down.  At this point, the device will begin emitting a flame rather than smoke.


SNAKES & STROBES

Consumer strobes are usually small paper cups filled with a liquid composition that is allowed to dry.  Strobe composition is a mixture that consists of two main parts: a composition that reacts easily, and one that doesn't.  When the fuse ignites the composition, the more reactive compound burns to create a large amount of heat.  This heats up the the more difficult to ignite portion of the mixture, which goes off with a sudden flash once it reaches ignition temperature.  This process repeats itself over and over, gradually increasing in frequency and producing hundreds of flashes.

In display fireworks, strobe composition is made into stars and put into either aerial shells or mines.

Snakes are made from a slow, cool-burning composition that leaves behind a solid, porous ash that "grows" out of the pellet as it burns.


SNAPS & PARTY POPPERS

These "trick noisemakers" have many different names, but they're all the same thing.  Each of these pea-sized devices contains a few grains of sand that have been coated with a tiny amount of impact-sensitive silver fulminate (AgONC), all twisted together in a piece of tissue paper.  When thrown on a hard surface (or squished between the fingers), the friction of the sand against the silver fulminate causes the latter to ignite with a quick, loud "pop".

Party poppers are another well-known and popular noisemaker, especially for children.  Inside of the plastic bottle, just above the neck, there's a small explosive charge connected to a string.  In the "bottle" portion of the popper are about a dozen tiny rolls of confetti paper.  The string is built into the explosive charge in such a way that when pulled tight, the charge explodes, which blasts off the paper end cap and sends out streams of confetti.

Neither pop-its nor party poppers are actually considered to be consumer fireworks.  Rather, they are considered "trick noisemakers" which, along with toy caps and cigarette loads, fit into the 1.4S category.  Therefore, they can be sold year-round in most toy shops and shopping centers.


SPARKLERS

Old-fashioned sparklers (left) consist simply of a thin metal wire that has been coated in a metallic pyrotechnic composition.  This slow-burning mixture is extremely bright and gives of thousands of tiny sparks as it burns down the length of the wire.  Newer, "Morning Glory" type sparklers (right) consist of a composition-filled tube attached to a wooden stick.

WHEELS AND SAXONS

Wheels consist of a cardboard frame to which are attached several small rockets, or "drivers".  The device is usually attached by a nail to a wooden post.  When the burning fuse enters each driver, the propellant burns rapidly to give off gas, which is forced out of the small nozzle to create thrust.  This thrust spins the device around its axis.  Unlike most rocket propellants (which are designed to lift the rocket up into the air and not give color), the propellant used in wheel drivers burns to produce rich colors, sparks, crackle, etc.  Because the wheel spins so fast, it appears that there are "rings" of fire.  When each driver is exhausted, the fire is transferred by another fuse to the next driver, which starts up again and continues the process (usually with a different effect).  This usually happens so fast that the wheel doesn't have time to stop spinning.


 

 

 

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All of the information, images, and diagrams on Pyro Universe are copyright 2001-2008 by Colin Bradley, unless otherwise noted.  They are the sole property of Colin Bradley and may not be sold, reproduced, or distributed in any form without permission from the owner.  This includes inserting any information or images from this site into another web page.  Information on this site can be used for reports, research papers, or other school projects, as long as the author is given proper credit by mentioning Pyro Universe in the bibliography (click here to learn how).

Disclaimer and Conditions of Use of Information on Pyro Universe

The information on this site is for educational purposes only.  The diagrams and procedures on this web site are simply to show the viewer how fireworks function and how they should be used properly.   Viewers are cautioned that they must form their own opinion as to the application of anything found on this web site.  Fireworks are hazardous devices that must be handled with care and used with common sense to avoid injury.  The author of Pyro Universe does not advocate the use of fireworks for illegal, unsafe, disruptive, or destructive purposes.  By reading the pages of Pyro Universe, you acknowledge that the author takes no responsibility for personal injuries, damage, or legal trouble caused by fireworks or the application of any of the materials presented at this site.  The reader is solely responsible for observing his/her local laws before using fireworks or applying the information presented at this site.