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Skylighter Newsletter #120 - How to Make a Fireworks Strobe Pots
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11/24/09 4:39 PM
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Skylighter Fireworks Tips
November 17th, 2008 -- Issue #120
IN THIS ISSUE:
Quick and Easy Strobe Pots
Save 25% with Skylighter's Strobe Pot Kit
Click Fireworks to Enlarge
20% off everything at Skylighter: Ends 11/27/08
Visit Skylighter's Project Plans
Safety should be your top priority. Read and review these
Fireworks Safety Articles before starting any fireworks project.
This time of year you're probably looking for nice, easy, bite-sized project to fill your pyro weekends.
This week Ned shows us how to make strobe pots. Strobe pots look fantastic against the snowy
backdrop. I even know one guy who makes 4 and 5-inch strobe pots he calls space station signals!
Skylighter aims to make your projects as simple as possible, along with detailed instructions from Ned
and kits containing everything you'll need. The new strobe kit, contains everything you'll need to start
making your first strobe pots. Just add a little Nitrocellulose lacquer and you're ready to go.
As if you needed any more incentive week only, you can knock 20% off everything at Skylighter.com.
- Harry Gilliam
Chief Cook & Bottle Washer
How To Make Flashing Fireworks Strobe Pots
By Ned Gorski
Safety
Whether you are new to fireworking or a seasoned veteran it always pays to regularly study good pyrosafety guidelines and to notice whether or not your work habits are conforming to those
recommendations.
Please refer to these links:
Fireworks Safety 101 by Kyle Kepley, intro by Ned Gorski
Fireworks Safety Manual, a collection of essays by Bill Ofca
Introduction
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Skylighter Newsletter #120 - How to Make a Fireworks Strobe Pots
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Close your eyes and listen to this music. What do you see when you do so?
Click here to listen to The Who
If you don't see a large fireworks mine-shot, followed by a line of 30-second strobe pots, ending with
another large mine-shot, then you really need to be subscribed to the Quilting-101 newsletter instead of
this one on making homemade fireworks.
Man, that music gets me in the mood for strobes. The first mine-shot would grab the attention of any
fireworks-display audience. Then the soft and subtle section of strobes would calm them down and get
them ready for their emotions to build during the show.
Strobe pots are among the simplest of fireworks devices and are easy to make. They can really add
some of that low-level variety to a pyro-display that so helps to keep an audience's attention.
"Hey, here's something different," they'll say to themselves as they stop, settle in, and start to pay
attention.
How do these pyrotechnic "twinklers" work?
It is not necessary, of course, to have a scientific understanding of strobes in order to make them. Like
baking a loaf of bread, chemistry is not necessary. All you need is a recipe, the right ingredients, and a
feel for the proper ways to manipulate those ingredients.
But, for the scientifically minded, there are a few informative resources, which explore the strobe
phenomenon in depth. In the 1979 edition of Pyrotechnica, Number 5, Robert Cardwell, the editor and
publisher of the Pyrotechnica series, wrote an article, Strobe Light Pyrotechnic Compositions: A
Review of Their Development and Use.
In this essay, Cardwell explores the historical development of strobing compositions and presents quite
a few different formulas.
Dr. Takeo Shimizu, in Fireworks, the Art, Science and Technique (FAST), originally published in 1981,
writes about "Twinklers," which is how he refers to strobing stars. He presents an outline of the
development of these strobing compositions, progressing during the second half of the 1900's.
Specifically Shimizu writes, "In Germany, U. Krone and F. W. Wasmann suggested that a twinkle
composition consists of two kinds of compositions mixed with each other, i.e. a smolder composition
and a flash composition…Ammonium perchlorate smolders when it is mixed with a small quantity of
magnesium. This can be used for the smolder composition. A mixture of magnesium and sulfate flashes
when it is heated to a high temperature. This can be used as the flash composition."
So, interestingly, a strobe composition is actually a mixture of these two types of comps, a smoldering
one and a flashing one. When the mixture is lit, the first one begins to smolder. When the heat rises
high enough, the flash comp ignites and emits a flash of light and heat. Then the mass returns to the
smoldering state until the heat rises high enough to repeat the flash.
In some compositions, magnesium-aluminum (magnalium) is used instead of the magnesium.
Magnesium requires a coating to prevent it from prematurely reacting with the oxidizer in the comp.
Additionally, sometimes barium nitrate or other oxidizers are used instead of ammonium perchlorate.
In 1987, John "Skip" Meinhart offered some details about his noteworthy strobing star formulas in
Pyrotechnica XI. Except for Shimizu's White formula, and Skip's Pink formula, all the rest of the
formulas use magnesium as the metallic fuel ingredient.
In the 1992 Pyrotechnica XIV edition Jennings-White explores Blue Strobe Light Pyrotechnic
Compositions. Up until that point in time, blue strobes had not been explored in depth because of some
unique problems associated with the chemical mixtures required to produce that color in a strobe.
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All of this information ought to be able to keep you reading until late into the night if you are so
inclined.
Making strobe pots
I won't be focusing on making strobing stars in this project, but only simple, ground-effect strobe pots.
I'm also not going to be making any of the formulations, which contain magnesium. As I said, using
that metal requires a special coating process because it does not form an oxidized protective layer on its
own, as do aluminum or magnalium.
There seems to be some debate as to whether or not magnalium needs to be treated and coated when it
is used in compositions containing ammonium perchlorate. Meinhart states, "I have had success using
magnalium powders that have not been treated with potassium dichromate. In practice I have often used
treated metal powders, but this does not always seem to be necessary."
Whereas in Hardt's Pyrotechnics, Barry Bush notes that the formulas he cites which contain magnalium
or magnesium in combination with ammonium perchlorate do "require the metal powders used to be
treated with potassium dichromate." Shimizu also specifies treated magnalium, and details the methods
of treatment in FAST.
Shimizu does state that if there is any reaction between magnalium and ammonium perchlorate, which
would be encouraged by the presence of water, it would only be a slow reaction in which the metal is
affected gradually.
I have used untreated magnalium in these formulas, with no problems. One sign of an unwanted
reaction would be the heating-up of the composition as I'm working with it, so I always pay attention to
see if that is occurring. I avoid adding any water to such a composition. I also don't store these devices
for long periods of time, which could produce a slow reaction of the ingredients, especially in the
presence of moisture.
So, I think I'll make simple white and pink strobe pots. The white formula is the most commonly cited
one:
White Strobe Composition
Chemical
Ammonium perchlorate
Magnalium*
Barium sulfate
Potassium dichromate
Percentage
0.57
0.24
0.14
0.05
16 Ounces
9.15 ounces
3.8 ounces
2.3 ounces
0.75 ounces
450 grams
257.1 grams
107.1 grams
64.3 grams
21.5 grams
* Shimizu specifies 80-mesh, whereas other sources specify 100-200-mesh. The mesh of the metal is
known to vary the flash rate of the strobe, so some experimentation is in order. Initially, I'll be using
200-mesh magnalium, Skylighter #CH2072.
Barry Bush has an interesting note in Pyrotechnics concerning this formula. This formula "may be
given a faster frequency by replacing the barium sulfate with anhydrous magnesium sulfate. The
resultant fast strobe is sometimes called a "shimmer effect." I'll have to try this sometime in aerial-shell
strobe-stars, since it is an effect I have admired in commercial shells.
Additionally, the flame created by this "white" composition is brilliant, but it does have a very slight
green tint caused by the barium. Barium normally produces very green flames with the addition of a
chlorine donor such as parlon or saran. Another experiment would be to include small amounts of these
chlorine donors to shift the color of the white strobe pots to green.
The pink strobe pot composition is as follows:
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Meinhart Pink Strobe Composition
Chemical
Ammonium perchlorate
Magnalium, 200 mesh
Strontium sulfate
Strontium carbonate
Parlon
Potassium dichromate
Percentage
0.57
0.15
0.11
0.08
0.04
0.05
16 ounces
9.15 ounces
2.45 ounces
1.85 ounces
1.2 ounces
0.6 ounces
0.75 ounces
450 grams
257.2 grams
68.6 grams
51.4 grams
34.3 grams
17.1 grams
21.4 grams
All the chemicals (except the magnalium, which I don't put through fine screens) are fine enough to
pass through a 100-mesh screen. If they are not, they are milled individually in a blade-type coffee
mill. See Fireworks Tips #112 for details and safety precautions concerning this procedure.
Note: Ammonium perchlorate does not play well with potassium nitrate. The combination forms
ammonium nitrate, which is very hygroscopic, attracting moisture out of the air like crazy, rendering
any mixture or composition containing it wet and useless. Don't grind either of these chemicals in a
coffee mill which has been used on the other chemical, unless the mill has been thoroughly cleaned
with soap and water.
Warning: Potassium dichromate is toxic and a known carcinogen. A good respirator and rubber gloves
are required when working with this chemical, and when using it in pyrotechnic compositions. Don't
breathe this stuff or get it on your skin.
All the chemicals for a given formula are weighed out individually and are passed through a 20-mesh
screen 3 times to thoroughly mix them.
Then the composition is mixed with enough nitrocellulose (N/C) lacquer (Skylighter #CH8198P) to
create thick putty, similar to Play-Do. I did not dilute the lacquer, but used it right out of the can, as-is.
The one-pound batches required 3 ounces, by weight, of the lacquer.
I started mixing the composition in a plastic tub with a paint stir-stick, and finished by kneading it with
gloved hands.
Mixing Nitrocellulose Lacquer Into Strobe-Pot Composition
The dough is then pushed with gloved fingers into paper tubes to create strobe pots. I start this process
by pushing the tube into the composition-putty to get the filling started.
Large pots can be made with 1.5-inch ID tubes, cut into 1.5-inch long sections. Or, smaller pots can be
made with 3/4-inch ID tubes, cut into one-inch long sections, or even longer. While thicker-walled
parallel tubes, like rocket tubes can be used, strobe-pot tubes do not need to be super-strong, so spiralwound tubes like Skylighter #TU2142 or TU2053 can be used.
Large diameter strobe pots would be appropriate for large displays and venues. Smaller ones are nice in
backyard size shows. Varying the length of the paper tube will adjust the total burn-time of the strobe
pots, so their duration can be dialed in for specific uses.
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For this project, I think I'll make mostly 3/4-inch ID by 1-inch long strobes to determine how well they
are working and how long they burn, plus a few other sizes to see how they perform, too.
Batch of "Flashing Fireworks" Made With One-Pound of Composition
Once the composition has been stuffed into the paper tubes, they are placed on their sides and set aside
on a tray to dry out in the open air. N/C lacquer releases acetone and other highly flammable solvents
as it dries, and I don't want these vapors collecting in my shop as this occurs.
Toward the end of the tube filling, the remaining strobe-putty started to dry out and became difficult to
consolidate into the tube. I added just a touch of acetone to the composition to re-dampen it.
It took 3 or 4 days for these pots to dry completely. When I tried to burn them before they were
completely dry, they did not burn with a regular strobing-action, but with a more continuous flame.
Priming the strobes
The dry pots will light well if they are ignited with a piece of Visco-fuse or with a propane torch. But
if I want them to ignite reliably with a fast-fuse or quickmatch line of fuse, then I need to prime them.
A black powder prime containing potassium nitrate cannot be used on these compositions because of
the incompatibilities between the nitrate and the ammonium perchlorate.
In FAST, Dr. Shimizu lists a different prime specifically for this use.
Ignition Composition for Twinklers
Chemical
Potassium perchlorate
Red gum
Charcoal, airfloat
Potassium dichromate
Aluminum*, flake 100-325
Percentage
0.74
0.12
0.06
0.05
0.03
16-Ounces
11.85 ounces
1.9 ounces
0.95 ounce
0.8 ounce
0.5 ounce
450 Grams
333 grams
54 grams
27 grams
22.5 grams
13.5 grams
*Skylighter #CH0174 aluminum would fit the bill in this prime.
After making sure all the individual chemicals (except the aluminum) will pass through a 100-mesh
screen, I weighed them out individually and mixed them together by passing them through the 20-mesh
screen three times.
I weighed out 1 ounce of the dry strobe prime composition, and added 1 ounce (by weight) of the
nitrocellulose lacquer. This created a wet prime comp that had a consistency between that of honey and
peanut butter.
I used a wood stick to apply this wet prime to one end of each strobe pot, and quickly pushed that wet
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I used a wood stick to apply this wet prime to one end of each strobe pot, and quickly pushed that wet
end into some dry strobe composition for the final prime layer.
Priming Strobe Pots for Easy Ignition
I perform one final operation to finish the individual strobe pots. I hot-glue a paper disc onto the
bottom of each pot. This prevents sparks and/or slag from dropping and igniting the bottom of a
twinkler prematurely as the pot burns. It also facilitates mounting the pots to a board when a show is
being set up.
Paper Discs Hot-Glued to the Bottom of Strobe Pots
Mounting and fusing strobe pots for use in a fireworks display
Once the individual strobe pots have been completed, they can be mounted to a board and fused for
easy installation out in the field prior to a fireworks show.
To do this, I simply hot-glue the pots to a board at the desired spacing. I find a spacing of 4 feet oncenter to work well. Then a run of quickmatch or tape-covered fast-fuse is used to fuse all the pots
together. A "window" is opened up in the quickmatch-pipe, and the bared black-match is taped on top
of the strobe pot with 3 wraps of masking tape.
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Strobe Pots Hot-Glued to a 1x2 Board, and Fused Together with Quickmatch
The quickmatch can be ignited by a piece of Visco-fuse, or an electric igniter can be employed, per the
information in Skylighter Fireworks Tips #'s 102 and 104.
Three Strobe Pots Ready to Be Electrically Fired
Results
I burned white and pink strobes made with the 200-mesh magnalium. The white one burned for 15
seconds with a very fast strobe rate of about 10 flashes per second. The pink one actually looked red,
burned for 23 seconds, and flashed about 4 times per second.
Warning: These strobe pots burn with an extremely brilliant flame and light. It is best to avoid looking
directly at them to prevent eye damage. Placing the pots where their light can reflect off of a structure
or trees makes their effect visible without having to look directly at them.
Strobe Smolder Phase, White Strobe Flash, and Red Strobe Flash
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Click here to see a video of the white and red strobes.
Flash
Video of Red and White Strobes
I liked the performance of the pink/red strobe, but the white one flashed too rapidly for my taste.
So, I made a new batch of each color using 60-mesh magnalium. I know that using a larger granulation
of the metal will slow down the burn time and also its strobe frequency.
Burning these new strobes produced the following results:
White strobe with 60-mesh magnalium, burned for 25 seconds, and flashed 1.5 times per second. I
found this to be a very pleasing strobe frequency.
Red strobe with 60-mesh magnalium burned for 27 seconds, flashed at a rate that varied from slow to
fast. This pot just couldn't seem to find a groove and settle into it.
Check out the video of these two types of strobe pots:
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Flash
Video of Red and White Strobes
Of the four variations I prefer the white strobe pots made with the 60-mesh magnalium, and the
pink/red twinklers made with the 200-mesh magnalium.
Although I made mostly 1-inch long twinklers, I also made some larger ones. Two-inch long ones,
made in the 3/4-inch ID tubes, burned as follows:
2-inch white strobe with 60-mesh magnalium burned for 40 seconds with about 2.5 flashes per
second,
2-inch long red strobe with 200-mesh magnalium burned for 40 seconds with flashes varying
from slow to fast again.
And, last but not least, I rigged up some white strobe pots using 60-mesh magnalium on a board and
accompanied them with the music I linked to right at the beginning of this article. You can get the idea
of what I had in mind in the first place as a nifty addition to a fireworks display. Click the video below
of the three white strobe pots accompanying Who's Won't Get Fooled Again.
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Flash
Video of White Strobes Set to Music
I do like what these simple, low-level ground devices can contribute to a fireworks show.
Enjoy,
Ned
[email protected]
Make Strobe Pots: Save 25% With Skylighter's Strobe Pot Kit
Get everything you need to make many, many bright white, twinkling strobe pots. The number of pots
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Ammonium Perchlorate (CH5000), 2 pounds
Magnalium (CH2073), 1 pound
Barium Sulfate, 1 pound
Potassium Dichromate, 1 pound
10 Tubes (TU2103), 1" ID x 2-1/2" long
10 Disks (DK1200), 1-1/4"
Visco Fuse (GN1005), 10 ft.
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Strobe Pot Kit, #KT1100
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Save 20% At Skylighter Until 11/27/08
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Sale ends midnight Eastern time, Thursday, November 27, 2008
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Skylighter's micro-star plates are being discontinued. Once we give away the ones we have this week,
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Why are they being discontinued? I would like to tell you it's because they didn't sell, or that they were
slow-sellers. I would even prefer to tell you that we can't get them any more. Truth be told: they rust.
Yep. Rust. Huh, rust? Yep, rust.
They were allegedly made from stainless steel. Apparently, the term "stainless" means something
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Other than that, they're fine. Spray 'em with WD-40 or oil 'em after use, and there's no reason they
won't last for years. But just sitting around here on the shelf, they rust. So I don't want to sully our
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All that being said, if you want to make a lotta really small stars, 2.5 mm in diameter, this star plate is
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we have revealed to our subscribers since June of 1999.
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Now obviously, our more recent articles contain our latest news, but this wealth of fireworks know-how is
still highly recommended reading. You’ll find lots of step-by-step instructions for making all kinds of
fireworks including stars, dragon eggs, comets, spin stabilized rockets, strobe rockets, whistle rockets, black
powder rockets, aerial shells, fountains, Class C fireworks displays, volcanoes, smokes, fuses, electric
matches, tourbillions, saxons, special effects fireballs, colored liquid fire, colored fireballs, mines, and much,
much more.
Check out all our back issues at:
http://www.skylighter.com/skylighter_info_pages/articles.asp
Tired of reading yet? Well, quit readin' and go out and LIGHT something!
Harry Gilliam -- Chief Cook & Bottle Washer
Skylighter, Inc.
<[email protected]>
540-338-3877
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