There are so many other kinds of fireworks like
mines, comets, gerbs, Roman candles, fountains,
and the spectacular girandola, rimmed with
rockets, that goes up in a spinning wheel of
glittering, noisy spiral trails.
BRINGING THE BOOM
At the heart of most fireworks is black powder,
made of three ingredients. Potassium nitrate
(KNO₃), is the oxidizer that provides oxygen for the
reaction. Charcoal is the fuel, and sulfur is a fuel
that serves to speed up the reaction.
Technically, black powder does not explode,
but burns very fast. The shell is wrapped tightly
to build up a lot of pressure so that it bursts with
great vigor. A dash of slow flash booster (KNO₃,
sulfur, and aluminum) gives it some extra pop!
Fine black powder coated onto rice hulls is
called burst powder and is used to fill up the inside
of shells. Granular black powder, grade 2FA, is
used for the lift charge to launch a shell. It is also
at the heart of stars, rocket fuels, and fuses.
Stars are typically composed of an oxidizer, a
fuel, a binder, and something to make it shine.
Copper compounds give a blue color, strontium
gives red, and barium gives green. Metal powders
make sparkles— typically aluminum, titanium,
magnesium, and iron.
HOW A SHELL IS MADE
For a double-petal ball shell, you start with two
hemis, or halves, of papier-mâché or plastic.
One has a passfire tube glued into it, which will
allow the fire to get into the finished shell. The
hemis are then lined with a layer of stars, a layer
of tissue paper, burst powder, more tissue, and
then the second layer of smaller stars to form the
inner petal. I made a 3D-printed jig to help place
these. The center of the shell has a final sphere
of burst powder inside.
The two hemis are put together and wrapped
with layers of gummed paper tape to give a dense
outer layer that allows plenty of pressure to build
up inside before the shell bursts!
» FREE DOWNLOAD: To learn more about DIY
fireworks, conventions, tools, and safety, get the
complete “Making Fireworks,” by Victor Chaney
and Ellen Webb, at makezine.com/go/fireworks.
Paper tape
Visco fuse
Burst powder
Inner star
Black match
Tissue paper
Hemi
Passfire tube
Lift cup
Cross match
DOUBLE-PETAL BALL SHELL DIAGRAM
Time fuse
Quickmatch fuse
Lift powder in baggie
Stars are placed in a hemi for a large shell.
A 3D-printed jig allows compaction of burst powder over
the outer petal of stars, saving space for the inner petal.
Wanda Garrett compresses fuel into a rocket with a
large press.
FIREWORKS
27
make.co
Victor Chaney, Mike Garret
M85_026-27_FireWorks_F1.indd 27M85_026-27_FireWorks_F1.indd 27 4/9/23 1:53 PM4/9/23 1:53 PM
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