Tuesday, July 22, 2008

Firework Types & How They Work

Roman Candles

A more complex firework, consisting of a tube containing pyrotechnic units alternating with propellant charges. When fired, the units are thrown into the air in sequence from top to bottom. Different effects are obtained by using successive units of varying colour and form. Roman Candles may also produce sound effects during their trajectory, including a report at the end. Between successive projections, the candle may emit coloured sparks or flame directly from the body.

They are made up to 60mm calibre and can send stars up to nearly 200 ft. The candle must therefore be securely fastened to a stake or candle frame.

It should be noted that as each successive star has further to travel up the case of the candle, it takes longer to exit the tube and is therefore subjected to the lifting charge for longer. The quantity of gunpowder has to be progressively decreased to achieve the same height. Do not use damaged candles – there could be a blow out.

Whilst the styles or effects have remained more or less unaltered throughout their history, there have been alterations in the method of activity of achieving the delay between the successive stars.

a) The original Ruggieri design utilised green mix gunpowder and these candles will emit showers of sparks between successive stars. It should be noted that with the exception of any tube products that may be used, all the products are consumed and there is little or no fallout.

b) Typical Chinese candles are used in vast quantities in the fireworks industry. Here a continuous fuse runs down the side of the tube and is designed to burn for the duration of the candle. The delay between successive stars is achieved by alternating them with loose plugs of potters clay. During the course of even a modest display, a considerable amount of clay is thrown into the air. Beware!

c) In recent Years Britannia Fireworks Ltd have been using “Typical” Chinese Candles manufactured using similar ideas to the “Ruggieri Technique”, and showers are emitted between each shot, this has enabled slightly better timing and larger stars etc.

d) To overcome the problems of achieving synchronised firing, there have been two developments, the earliest being the substitution of the green mix delay with a felt plug with a pressed delay in the centre. These felt plugs return to Earth unburnt.


A shell is a hollow projectile containing an explosive charge. In Western Europe and the USA the shell may also have an attached lifting charge. It must be remembered that this practice is by no means universal and the presence of a lifting charge would not be considered a defining characteristic by firework technicians. (The presence of a propellant charge is considered a defining characteristic of a rocket!)

The shell is projected from a mortar tube by a charge of gunpowder (the lifting charge) to burst high in the air with whatever effect is incorporated in the shell.

The mortar tube may be made from cardboard, fibreboard or specific types of plastic.

The shells may be made from paper or plastic and are either spherical or cylindrical in shape. It is much easier to contrive multiple breaks or bursts with a cylindrical shell, whereas the spherical shells are required to produce spherical bursts, chrysanthemums, peonies.

Shells which explode with a loud report are called maroons or salutes

The diameter of shells used at Britannia Fireworks Ltd are generally anything from 2” to 12” and come in two types:-

a) Bottom fused and

b) Top fused

Bottom fused shells have their lifting charge ignited first. This in turn ignites a delay fuse to the bursting charge.

Top fused shells are fitted with a delay fuse to the bursting charge with a secondary instantaneous fuse to the lifting charge. These are perhaps a little more reliable as there is less risk of the delay fuse being blown out. These tend to be more cylindrical in shape. Care must be taken when installing top fused shells to avoid damage to this lifting charge fuse. It is also essential to ensure that the shell, as with all shells, is inserted into the tube the right way up. Damaged shells should not be used.

Shells can be extremely dangerous if they are not handled and fired in the approved manner. The exit velocity of a shell from the mortar tube could be in excess of 200 mph!

To appreciate the height and effect of a shell, the following can be used as a rough guide

If ‘x’ is the calibre of the shell in inches,

the delay to full height is ‘x’ seconds,

the height reached is ‘X’ x 100 feet,

the spread of burst is ‘X’ x 10 metres.

This will not always apply, however it can be used as a guide for most shells.


These can be regarded as similar to shells in the method of use. The important distinction between them is that the firework element is ignited in the tube and is already burning when it exits the tube.

The effect of a mine is therefore instantaneous from the spectators viewpoint and always lower, although heights of 100 ft. may still be reached. These produce effects of stars, bombettes, whistles etc. Special care must be given when loading the bag type mines.

It is sometimes extremely difficult to distinguish the difference between some cylindrical mines and cylindrical shells and there are even some spherical mines.

Multi Shot Barrages or “Cakes”

These fireworks known affectionately as “cakes” are actually a collection of other categories of fireworks grouped together in boxes and produce stars, bombettes, whistles, spinners, etc. They may vary in size from small packages up to large cardboard boxes which can be very heavy to handle.

A cake barrage may contain anything from say 36 x 2.5”” shells in light tubes, 100 x 30mm maroons or even up to 1000 roman candles one shot in each tube.

They are extremely powerful so please be careful! They need to be set up very carefully, with particular attention paid to the surface upon which they stand and secured to a series of stakes. Cakes should always be angled away from spectators.

It is important to ensure that they are the right way up! It is not unknown for them to be labelled upside down or even the larger ones to be packed into their boxes upside down. Please take note !

Due to the size of some Cakes and the calibres used, we recommend moving them at least 50 metres, and in some cases even further (refer to Britannia Fireworks Site Policy)

Cake barrages are boxes containing a number of separate items, fused together so that they are fired in sequence over some period of time, normally much longer than for a single firework. The items may be all of one kind, or a mixture, including small, shells, candles etc.

As with roman candles, once started, the firing continues automatically until the last item is reached.

Batteries are comprised of a number of fireworks, normally of the same type, grouped in a single layout, to be fired as a single unit, individually in sequence, or in any other combination. The effect is the same as from any one firework on its own, enhanced by sequential or multiple firing.

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