Confessions of a Fireworks Man

Gary Smith's Secret to Making Roman Candles

By Ned Gorski

What's All the Mystery about Making Roman Candle Fireworks?

I really like Roman candles. But even though Roman candles appear to be the simplest of fireworks devices, they are a real challenge to make so that they perform consistently. Especially if you use the traditional methods you'll find in all the books.

I'm going to show you a secret method for making Roman candles that you haven't seen before. I promise you absolutely will not find Roman candles made like these in any of the books (at least, not yet!). Best of all, you can use this new method to overcome all the Roman candle problems that traditional candle-making methods create.

Look. Where rubber hits the road is how well your fire works in a fireworks display, right? Well, read on and learn how Roman candles work, what goes wrong, and how to make Roman candles like nobody you know has ever seen.

Here's a video of one of the first successful Roman candles I made using the method I'm about to teach you.

Video of an 8-Shot Silver
Streamer Star Roman Candle

Notice now consistent the timing is between the shots. One star is coming down and going out, quickly followed by the next shot. That kind of consistency and effect is what I was going for. And that's what is hardest to achieve using traditional Roman candle fireworks-making techniques.

With all the candles I've made using this new method, the timing between shots has been within one second of each other. If you talk with pyrotechnics folks who have made their own Roman candles, they'll tell you how remarkable that is.

You see, anyone can learn how to make a Roman candle, but making them so that the timing and height of the shots is consistent, well that's what you don't see very often. Of course, Roman candle fireworks are a great way to test the color, burn time, effect and ignitability of your new star compositions. And a single candle is just fun to light, sit back, and enjoy. You can gang multiple candles together, say 7 of them in a bundle, or set them up in a fanned rack to fill the sky from left to right with Roman candles' shots.

So Why is a Roman Candle Firework Called Roman?

Despite the fact that we Gorskis prefer to call these devices "Polish Candles," for some reason that name has not caught on yet. So, why were these devices called "Roman candles" to begin with?

It seems that as far back as the early 1800's, both French and Italian authors were using the term "Roman candles" to describe such devices. Since Italy was one of the countries which greatly influenced the development of fireworks, it is not very surprising that one of its most prominent fireworks devices would have its name associated with its greatest city, and the name of its once-sprawling empire.

Exactly What Is a Roman Candle?

Traditionally, a Roman candle has been thought of as a single-tube fireworks device which fires multiple, consecutive shots of projectiles skyward, and which emits a fountain-like spray of sparks between shots.

Those projectiles can be individual firework stars, comets with various colors and effects, single crossette comets, mine-shots of multiple stars, combination star-and-report devices, or small aerial star shells.

A Four-Pack of Consumer-Fireworks Roman Candles

But one comet fired skyward from a mortar is sometimes considered to be a single-shot Roman candle. And indeed, single-shot candles, arranged in fan-shaped mortar racks, have become common in many modern displays.

Consumer-firework Roman candles can be as small as 1/2-inch inside-diameter tubes, and large professional-display candles can be found with a tube ID as large as 3 inches.

I'd suppose if you asked someone, "What are the most common types of fireworks you can think of," the response would be something like, "Firecrackers, sparklers, bottle-rockets, and Roman candles."

Certainly Roman candles play a part in many of our childhood fireworks memories. Often they were held in our hands as they fired, but there have been so many mishaps resulting from malfunctioning candles that hand-held Roman candles are now discouraged.

I once made the mistake of thinking I could hold a one-inch display candle in my hand as it fired. The first shot propelled a star skyward, and the rest of the candle backward out of my hand to who-knew-where. I had to quickly find it and stabilize it with my foot as it finished firing. I still haven't lived that down in my local fireworks guild. I don't recommend you try any similar stunts.

With these larger Roman candles, it's best to tape them to a stake and firmly secure them to the ground before ignition.

How Is a Roman Candle Constructed?

The most common, and traditional method of Roman-candle construction involves alternating layers of black-powder lift charge, cylindrical stars, and a slow-burning candle/delay composition, with the bottom of the tube plugged with a clay bulkhead.

Roman Candle Cross-Section

If you imagine lighting the candle's fuse, it will burn down until it ignites the first increment of the delay composition. That rammed increment burns slowly like a gerb (fountain), spraying sparks out of the end of the tube, which would normally be pointing skyward. Of course, when I say "normally be pointing skyward," this "dog and Roman candle" video from YouTube pops into my mind: http://www.youtube.com/watch?v=i8mDAae7LEY. That one shot just about takes out the kid and the old man at the same time!

When the last part of that first increment of delay composition burns through to the first star, the prime on the star burns quickly and ignites its whole surface. That, in turn, lights the first layer of black-powder lift charge, which propels the star out of the tube. At the same time, the top of the second increment of candle composition is ignited, which begins a repeat of the whole process.

The Roman candle in the sketch is called a "four-ball" Roman candle, since it will sequentially shoot four stars out of the tube. "Ball" refers to the ascending ball of flame each star will produce.

Typically candles are made with pumped, cylindrical stars, which have flat bottoms and tops. The flat bottom holds the black-powder lift charge in place, and the flat top supports the delay composition nicely.

Why Do I Make Roman Candles?

In the past 20 years or so in this hobby, I've only tried to make Roman candles a few times, although they are among the most elementary of devices. Quite honestly, in those attempts I was never completely satisfied with the results.

And you know what's funny? Even though I'd made 16-inch aerial fireworks shells and 36-inch diameter girandolas, I felt like I couldn't make a consistently performing Roman candle that would live up to my expectations.

One reason I wanted to get good at producing nice little Roman candles is that they can be fired in any location suitable for the discharge of consumer fireworks. Big fireworks devices like big shells and girandolas require a big display site and a display permit. But it's nice now and then to make a little rocket or Roman candle and be able to take it outside to shoot and see how it performs.

In his 1947 book "Pyrotechnics," George Weingart has a section on rolling cases (tubes), for Roman candles. He also has instructions for making an individual, 3/8-inch ID, eight-ball Roman candle.

Weingart describes a simple machine for mass-producing consumer-fireworks candles. I have seen the remains of a similar machine at the Rozzi's Famous Fireworks plant near Cincinnati, Ohio. My understanding is that the machine I saw was the very one Weingart based his sketches and descriptions on.

Weingart's Sketch of a Roman
Candle Making Machine

How to Make a Roman Candle

I've seen traditional Roman-candle-making instructions elsewhere, and they seldom differ significantly from the ones in Weingart.

A parallel tube is plugged at the bottom with a rammed increment of clay or with a glued-in section of wooden dowel. A scoop of black-powder lift charge is loosely put into the tube, followed by a star, which fits nicely into the tube. This is capped off with an increment of the candle-composition delay powder, which is rammed "with about six light blows of a small mallet" according to Weingart.

And this is where Roman-candle construction gets tricky. That increment of delay composition must be rammed solidly enough to get it really consolidated and locked into the tube. That is necessary in order to prevent fire from being prematurely blown down the tube past it when the star above that increment is shot out of the tube.

The delay charge must also be in the tube tightly enough that fire cannot creep between it and the inner tube wall as it burns, which would also prematurely ignite the star below it.

If you've ever rammed fountain composition in a paper tube, you know it takes a fair amount of force to solidly compact the powder, in order to produce the right effect when the fountain is lit.

But, when one is ramming Roman-candle delay composition, that increment sits on top of a loose star sitting on loosely granulated black-powder lift charge. This is an inherent conflict: not an ideal situation for getting a solidly compacted increment of delay composition.

And here's what you see as a result--the most commonly seen Roman-candle failures--stars which fire from the tube in a rapid-fire, unevenly-paced manner; sometimes more than one star fires at once; or the paper tube ruptures because of the amount of pyrotechnic material, which ignites everything at once prematurely.

All of this results from not having a solid base on which to ram each increment of candle composition. That makes the construction of these simple devices a real challenge, especially in candles larger than about a half-inch ID. Larger diameter delay increments are harder to solidly compact sufficiently than smaller diameter ones.

There must be a better way.

Enter my pyro buddy, Gary Smith. Recently on Passfire.com Gary posted a video of a fairly complex Roman candle he'd made. The individual shots were color-to-report inserts, which are harder to make than simple stars.

But, what I noticed immediately was that his shots were very evenly spaced apart, and that there was a nice fountain of fire-dust spewing from the mouth of the tube between shots.

This was a very nicely constructed, consistently-performing Roman candle, that I knew from personal experience was hard to achieve. I simply had to know more. Gary was kind enough to share with you and me the unique method he developed of achieving nicely compacted, traditional delay increments between the shots. And that is what produced the consistent effects, which so impressed me when I first saw his video.

Using Multiple Tubes to Make One Roman Candle

Huh? Say what?

I thought we'd already defined a Roman candle as a "single-tube fireworks device which fires multiple, consecutive shots of projectiles skyward."

How can we use more than one tube to make a Roman candle?

Well, therein lies Gary's trick, which hopefully will forever be known as the "Smith Method" of constructing candles.

Looking at the sketch of the Roman candle above once again, you'll notice there is a recessed, empty space below the clay bulkhead in the paper tube. Putting the tube on a base, which has a ramming nipple, and then dropping loose clay into the tube and ramming it with a drift and mallet creates that void.

Materials and Tools Ready to Ram
Clay Plug in Paper Tube

Way back in Skylighter Newsletter #89, I gave directions for mixing clay nozzle and bulkhead mixes. I also showed how to ram nozzles and bulkheads, and a photograph of a cutaway tube with a nozzle rammed in it.

Either of those clay mixes is usable for the clay plug at the bottom of a Roman candle. And the photo shows how a clay nozzle or bulkhead locks into a paper tube by slightly expanding the tube in that area.

Cutaway Paper Tube Showing Locked-In Clay Bulkhead

I can just imagine Gary thinking, "How can I get each delay increment solidly locked into the paper tube the same way the clay plug is?"

And then the light went on in his head: "Cut the tube into sections, ram each delay increment solidly into its section, and then reassemble the tube sections into one solid case."

I imagine a picture popping into his mind something like the sketch below.

The Tube Sections of a Smith Method Roman Candle

Although the sketch shows a 4-ball candle, additional 2-inch middle sections can be added or removed to increase or decrease the number of shots.

Note: The top, 3-inch or longer tube section creates the first "mortar" out of which the first star is shot. Within certain limits, the length of a mortar determines how high the projectile goes. Technically, 3 inches is the shortest practical tube from which to shoot the first star. But with a tube that short, the first shot will not go as high as the shots that follow it. So, I actually prefer to use a top tube section that's 5-inches long.

I have arrived at the specific dimensions for this particular Roman candle based on my particular stars and delay composition. To the left of each increment of the delay (candle) comp there is a 1/2-inch void just like the one to the left of the clay plug.

The nipple on the ramming base creates this 1/2-inch recess in each section. A tube section is slipped onto the ramming base. The proper amount of delay composition is loaded into the tube and then rammed with a drift and mallet.

This creates a very solid, securely positioned increment of delay composition, which prevents most types of Roman candle failures.

There it is, simple as that: the Smith secret to Roman candle construction.

Now, here's how to make a Roman candle using this method to show all the steps involved.

Now, How to Make a Roman Candle

For this Roman candle, I'm going to alternate shots of D1 glitter stars with shots of Willow Diadem silver-streamer stars. First a glitter shot, then a silver streamer, then glitter, silver streamer, etc. The candle in the video at the beginning had only silver-streamer stars.

For the willow diadem stars, I'm still using the total amount of metal that is specified in the formula. But rather than using three different types of metal, I'm only using fine, spherical titanium, Skylighter #CH3010. This long-burning star leaves a nice, long silver tail behind it that "pops" as the bits of titanium catch fire and burn.

The dimensions in the sketch above are based on my primed 5/8-inch diameter, 5/8-inch long pumped stars, which I made the same way I made the gold-glitter comets in Fireworks Tips #111.

I prime the ends and sides of the stars so that fire is transferred as quickly as possible from the top to the bottom of the star. The final primed stars end up being a little under 3/4-inch diameter and about 3/4-inch long.

The star dimensions dictate that I use 3/4-inch ID parallel tubes for this project. Either the extra-strong, 1/8-inch wall Skylighter TU1066 tubes, or the standard, 1/4-inch wall Skylighter TU1065 tubes will work well in this project.

These long tubes work well because they can be marked, and all the Roman candle sections can be cut out of one length of tube. This makes it easy to reassemble the sections later on.

I want to make an 8-shot candle, so I mark and cut a tube as shown below. I write a number on each section, starting with #1 at the bottom of the tube.

Roman Candle Tube Marked into Numbered Sections before Cutting

The markings will enable me to reassemble the tube sections exactly as they came apart, which will increase the potential for me to arrive at a nice straight finished candle. I allow about 1/16-inch for each of the saw cuts.

In the drawing above, notice that there will be a star at each of the cuts. So I mark 8 cuts, plus the cut at the top of the candle. The bottom section will be 1.5-inches long and the top one will be 3-inches long.

Then I cut the tube into sections.

Cutting Paper Tube into Sections

Roman Candle Tube Cut into Sections

I use a little sandpaper to smooth the inside and outside edges of each end of the tube sections. Smooth ends make for smooth reassembly later on.

Sanding Ends of Roman Candle Tube Sections

Now I put section #1 on the nipple of the ramming block with the bottom of the tube down.

I made the ramming base and nipple by drilling halfway through a piece of 3/4-inch thick plywood, and epoxying a length of 3/4-inch diameter aluminum rod into the hole. I got the rod from Home Depot (in the nuts-and-bolts aisle where they have a rack of metal rods and angles), and cut it with a hack saw just long enough that 1/2-inch of it projects from the plywood. I used a file to smooth the top end and edges.

Ramming Base with Aluminum Nipple and Section #1

I load 10 grams (one flat 1/2-tablespoon) of bulkhead-clay mix through a funnel into the tube. When loading the clay into the short tube through the funnel, I use a 1/2-inch wooden dowel to push the clay through the funnel and slightly compact it into the tube. This helps get all the clay through the funnel and down into the short tube, so it doesn't spill out over the top.

I ram the clay plug with a 3/4-inch rammer from one of my sets of rocket tooling, and 8 moderate blows with the rawhide mallet. This results in a 1/2-inch thick plug in the tube section. A section of 3/4-inch wooden dowel could certainly be used as a rammer in this project, as shown in the article on making gerbs.

Ramming Clay Plug into Roman Candle Bottom Section

Note: I want to fully consolidate the clay and lock it into the tube without damaging or splitting the tube. This takes a bit of practice. With the softer, standard tubes, a slight bulge will form in the tube, which can be felt if one runs their fingers up and down the tube.

Now it's time to ram the delay-composition increments into the other sections of the tube. I have played with a variety of delay compositions, from relatively fast-burning ones to those that are slower burning. I like to keep the delay increments about 1-inch long between the stars. This provides a nice, solid plug, which does not allow fire to pass prematurely around it.

So, the burning speed of those 1-inch increments determines how much time there is between shots of the Roman candle. With the stars I am using, I prefer the timing I get using the following candle delay composition (This is a classic star formula which can be found in various books).

Chrysanthemum 8 (from Shimizu) Delay Composition

Chemical	%	79-gram batch
Potassium nitrate	0.49	35 grams
Charcoal (airfloat)	0.40	29 grams
Sulfur	0.06	4 grams
Dextrin	0.05	4 grams
Water	+0.10	7 grams
Total	1.10	79 grams

Note: The weights have been rounded off, and this size batch will make enough composition for the 8-shot Roman candle I'm making.

I grind the potassium nitrate in a blade-type coffee mill fine enough to pass a 100-mesh screen. I do the same with the sulfur. The charcoal and dextrin are already that fine.

Grinding Potassium Nitrate in a Coffee Mill

25-50% of the airfloat charcoal can be replaced with 80-mesh or even coarser charcoal for longer hanging sparks in the fountain plume between candle shots.

The chemicals are put in a sealed plastic tub and shaken to mix them. Then they are worked through a 20-mesh screen or kitchen colander 3 times to thoroughly mix them and break up any remaining clumps of chemical.

Sifting Powder through Screen

Using a spray bottle, I spritz the composition with water as it sits in a plastic tub on a scale, until 7 grams of water has been added. Between every couple of spritzes, I swirl the comp in the tub to spread the water around.

I work the water into the powder with gloved hands and then push the damp composition through the 20-mesh colander twice to really integrate the water.

Working Water into Delay Composition

Then, just as I did with the increment of the clay in tube section #1, I ram increments of the still-damp delay composition into the remaining tube sections. I always place each section with its bottom down on the ramming nipple. This creates that 1/2-inch void in the bottom of each section as shown in the sketch.

Sections #2 through #8 now get 10 grams of the composition rammed into them. Ramming that amount of comp yields delay increments that are 1-inch long in each section. Finally, I ram 5 grams of the composition in tube section #9, which produces a 1/2-inch long delay increment.

Then I allow the delay increments to dry overnight, using my drying box. They would dry in a few days if they were put in a warm location of the storage area.

Note: Often, directions for making candles specify ramming dry, granulated delay composition. At first I wondered if I should granulate and dry the comp, and I discussed this with Gary. His theory is that damp composition slightly wets the adhesive layer inside a paper tube, and when it dries it really glues the delay increment in place. Makes sense to me, and ramming it damp really creates a dense, hard plug of composition.

Once the tube sections and delay increments are dry, it's time to assemble the sections of the Roman candle, with lift charges and stars installed as I go along.

One homemade jig really helps at this stage, and ensures the assembled Roman candle ends up perfectly straight. I took this tip from one of the photos of Gary's process, and expanded upon it for my own purposes.

Homemade Jig for Assembling Roman Candle Sections

The jig is made up of two, 36-inch long pieces of 1-inch by 1-inch aluminum angle channel from the same section of Home Depot mentioned above. One of the pieces has two 1/4-inch diameter, 2-inch long carriage bolts and nuts installed in each end to act as feet to stabilize the channel during use.

I lay out the now-dry candle tube sections in numerical order on the jig. I also lay out my stars in the order in which I want them fired, along with a cup of FFg sporting-grade black powder from a gun shop.

Of course, with a bit of dialing in, I could also use my homemade black powde for the lift.

I'll be using Elmer's glue to assemble the candle and a 1/4-teaspoon kitchen scoop to measure the black powder lift charges.

Assembling Roman Candle Tube Sections

I have cut out little disks of tissue paper the same diameter as the tube OD to go between the stars and the lift powder. The tissue prevents the black powder from migrating up past the star between the star and the inner wall of the tube. I want to keep all the lift powder down below the star to maximize the star's propulsion out of the tube.

Roman Candle Parts--Ready to Assemble

To assemble section #1, I stand it, bottom down, on my workbench, and drop 1/4-teaspoonful of the black powder into the top of that section through a little funnel. I place a tissue paper disk over the top of the tube and push a star and the tissue down into the tube, seating it firmly against the black powder. Then I apply a thin ring of Elmer's glue around the top edge of that section.

First Roman Candle Section--
Loaded with Lift Powder,
Tissue Paper Disk and Star,
Elmer's Glue Applied

I then push section #2, bottom down, onto the glued section #1, and wipe any excess glue off with a paper towel. Then, while I'm pressing those sections together, I pick them up and lay them into the trough of the alignment jig. Pushing them down on the jig ensures that they are perfectly aligned, and I push them together end-to-end to make sure the glue joint holds tight.

Tube Sections 1 and 2 Glued
Together and Aligned on the Jig

Then I carefully pick them up, continuing to press the sections together, and stand the assembly upright.

Again I load lift powder, tissue, and star, and run a ring of glue around the top of the tube. Then, I assemble section #3 in the same manner as #2.

I repeat this process until all nine sections have been assembled and I have the whole shebang resting in the jig.

All Sections of Roman Candle
Glued Together and Aligned

I could just press the sections together end-to-end, make sure they're sitting nice and straight on the jig, and let the glue dry. But, nooo, not me. I'm a bit more of a perfectionist than that.

Note: That's kind of a funny revelation. When I was a kid, my Dad was always hollerin' at me for not cleaning up his shop after using his tools, or for not finishing up a project I'd started. Now, with my pyro avocation, I've gotten very particular about cleanliness in my shop in order to prevent serious accidents. And I've also come to know that meticulous work habits are a sure way to achieve consistency with my artistic fireworks devices. We live and learn. Sorry, Dad, and thanks; I finally got it!

So, I go one more step to really clamp the candle sections tightly, end-to-end as the glue dries, and to ensure my candle ends up perfectly straight when it's dry.

I lay another piece of the aluminum angle channel on top of the glued-up candle. (You were wondering what that extra piece was for in the pictures above, right?)

Roman Candle Sandwiched Between
Two Aluminum-Angle Sections

Then I take 12-inch pieces of masking tape and put bands of the tape, stretched tightly with the sticky-side-out, around the aluminum and candle sandwich. This really holds the glued tube sections nice and straight.

Masking Tape, Sticky-Side-Out,
Holding Tube Sections Straight

To really pull the tube sections tightly together as the glue dries, I install two 1/2-inch square, 4-inch long, pieces of steel bar, and two tightened strap clamps. Gently tightening the clamps snugs the tube sections together, but I don't tighten them so much that the ends of the tubes are damaged.

Of course, long rubber bands or elastic bungee cords could be used in place of the strap clamps. Pieces of wood could also be used instead of the steel crossbars.

Pulling the Tube Sections Together with
Steel Bars and Strap Clamps

It takes 2-3 hours for the glue to dry sufficiently to allow the assembled candle to be removed from the jig. I remove the strap clamps and steel bars, tear the bands of masking tape, which remove easily because they were applied, sticky-side-out. Et voilà! A sturdy, straight Roman candle emerges.

A little 100-grit sandpaper quickly knocks any rough spots off the outside of the tube joints.

Dry and Sanded Roman
Candle Removed from Jig

Well, let's stick a piece of Visco fuse into this puppy, take 'er outside, and fire it up. Right?

Hold on there, podnah. Not so quick. The candle tube, as it currently is, really is not that strong yet. End-to-end glue joints don't have much structural integrity. If this particular Roman candle is going to survive the pressures when it fires, those joints will have to be reinforced a teensy bit.

Reinforcing and Finishing the Roman Candle

Enter fiber-reinforced, gummed, kraft-paper tape. One of my favorite supplies is a tape that I get from Staples: 2.8-inch wide, fiberglass reinforced, paper packaging tape, Staples #468231. This stuff is light, thin, and really molds well to the tube once it's wet.

Although I usually cut the tape to length with scissors because of the fiber-reinforcement, I use my manual tape dispenser as a wetting station to wet the tape. A sponge could also serve this purpose.

Fiber-Reinforced, Gummed
Kraft Tape, and Manual Tape Dispenser

The glued-together candle is 18.5-inches long. I cut four 18-inch strips of the kraft tape to use to reinforce the tube. Each strip will run lengthwise on the tube, and will wrap around to cover about 3/4 of the tube circumference. Therefore, the four strips, staggered as they are applied, will create 3 complete layers of tape on the candle.

Four 18-Inch Strips of
Tape for Reinforcing Candle Tube

I run a strip of tape through the dispenser's wetting station, and carefully apply it lengthwise on the Roman candle tube. Each strip has to be kept straight; the long edge of the tape needs to be parallel to the length of the tube. I get the first strip pasted down tight. Then, I butt the long edge of a new strip right up against the edge of the first piece of tape. Since each strip only wraps around 3/4 of the tube's circumference, once it is pasted down, the second piece of tape will overlap the first one some. I repeat this process for all 4 pieces of tape. That way the gaps in the tape get staggered around the circumference of the tube.

In between each strip application, I burnish the previous strip down nice and smooth with a scrap of paper tube. When all the strips are on, I give the whole tube a nice hard burnishing to produce a flat, smooth application of all the tape.

Kraft Tape Applied to Tube
and Burnished Smooth
with Paper Tube Section

Oh, yeah, that baby's looking nice, and feeling strong now. After inserting a hooked piece of Visco fuse as shown in the candle cross-section sketch, I put on a wrapping of colorful paper, and tie the paper snug around the fuse. Now she's ready to take out, tape to a stake in the ground, and light.

Completed Roman
Candle Ready to Fire

3 Finished Roman Candles

Conclusion

You might be thinking, "That was a lot of work to produce one, simple fireworks device, wasn't it?"

Naah. Not really. There was probably about an hour's worth of work in the construction of that one candle, all told. It may sound like a lot of time and effort, but once you get going on the project, it's really not that complicated.

This new Smith Method of making Roman candles is such an improvement and can produce such nice consistent results for the hobbyist, that I just can't help but be excited about it, especially after my past, less satisfying results.

When I carefully look at the videos of all the Roman candles I made using this new method, every initial delay after ignition was just about exactly 4 seconds, and every intermediate delay was within one second of 8-seconds long. It don't get no better than that.

On top of that, I'm already imagining creative variations on the above theme: mine-shot candles, crossette-comet candles, color-to-report-insert candles, married-comet ones, matrix-comet projectiles, and crackling-microstar-comet varieties.

I hope to tackle those projects in the coming months.

Additionally, the Roman-candle competition at the PGI (Pyrotechnics Guild International) convention allows candles up to 2-inches ID. I do have some nice, stout 1.5-inch ID tubes, so I just may have to come up with some larger versions of these babies to take to Mason City, Iowa in August.

Have fun and Stay Green,
Ned
ngorski@skylighter.com

How to Make a Fireworks Strobe Rocket

By Ned Gorski

What is a Strobe Rocket?

If I had to make the choice of being able to construct only one type of rocket, it would be a difficult decision. I truly love the low-level simplicity and effect of the Spectacular Glitter-Tailed Rocket with Willow-Diadem-Horsetail Finish.

But for pure, high-powered, awe-inspiring and crowd-pleasing rocketry display, the strobe rocket is sure hard to beat.

Video of One-Pound Fireworks Strobe Rocket

The following video is a six-pound strobe rocket. I constructed this 1.5-inch ID model in a seminar I taught at a local pyro club event.

Note: The "one-pound" and "six-pound" rocket motor designations have nothing to do with what the rocket actually weighs. They are fireworking terms, which refer to the rocket engine tube's inside diameter (ID), and have their roots in antique rocket-making terminology.

Video of Six-Pound Fireworks Strobe Rocket

(Video taken by Dan Thames)

That baby was really up there by the end of its flight. You can tell that from the delay between the video and audio of the report heading. These large strobe rocket engines really do sound like helicopters in flight, too. For such a relatively simple fireworks device, they sure are satisfying and attention grabbing when they work well.

Even when they don't "work well," and CATO (blow up) on the launch pad, these rockets are impressive! There is a lot of power packed into that engine tube, so it pays to put a long piece of Visco fuse on them, and have everyone plenty far away from the launch area just in case.

Whistle Rocket Explosion on Launch Pad

(Photo Courtesy Jerry Durand)

This is the third in a series of whistle-related articles. The first installment dealt with making whistle fuel and simple fireworks whistles. That same fuel will be used in these strobe rockets. The second article described the construction of basic whistle rockets. Many of those same techniques will be used now to make strobe rockets. So, it's a good idea for you to familiarize yourself with those basic methods before forging ahead with this project.

Note: I will not be repeating all the basic construction details from the whistle rocket tutorial. You really will need to be familiar with those techniques if you are going to tackle this strobe rocket project.

A strobe rocket utilizes whistle fuel for power, along with strobe fuel to create the popping sound and flashing light that is unique to them.

Pressing Rockets

Note: Once again, as in the whistle projects, hand ramming with a mallet is never employed with these fuels and devices. Only a press equipped with a safety shield should be used to press these items. Fireworks Tips #121 detailed the construction of such a hydraulic rocket press. For small rockets, some folks use a manual arbor press to consolidate (press) the fuels.

Hydraulic Rocket Press with Safety Shield

Strobe Rocket Fuel

In addition to the whistle fuel I referred to above, one other fuel is necessary for these strobing rockets--strobe fuel. This fuel is very similar to the composition that was used to make strobe pots. Please study the methods and precautions that were spelled out in that essay.

This strobe fuel is what gives these rockets their distinctive popping sound and flashing light as they fly. But, strobe fuel alone is not powerful enough to make a rocket fly.

Back in the '80's, Doc Barr started playing with a basic strobe rocket, using a black powder fuel to boost the strobe fuel's power. His results are chronicled on Page 58 of The Best of AFN II.

A funny and educational quote from Doc's article is, "All rockets have the potential of exploding on takeoff, but these do it with an annoying frequency. About 1 out of 10 act more like an open-ended salute than a rocket. So 'light fuse and retire quickly' is my Eleventh Commandment."

In the late 80's and early 90's, folks like Doc and Steve LaDuke started working with whistle fuels in rockets, resulting in the high-powered fireworks whistle rockets like I described in the whistle rocket article mentioned above.

Somewhere along the line, these rocketry pioneers had the bright idea to combine the powerful whistle booster fuel with the impressive strobing fuel, and the modern strobe rocket was born.

Traditionally, nitrocellulose (NC) lacquer is added to the standard white strobe composition specified in my strobe pot article. In his BAFN article, Doc Barr said he pressed his strobe fuel slightly dampened with NC lacquer. Many modern builders dampen their fuel with NC lacquer, granulate the dampened fuel through a 12-mesh screen, and dry the granules before pressing the fuel in the rocket motor.

Years ago I made a slight change in this method. Rather than using NC lacquer, I now dampen my strobe fuel with an additional 2% mineral oil dispersed in Coleman Fuel, as I described in the whistle-fuel procedure.

White Strobe rocket Fuel

Chemical	Percentage	16 Ounces	450 Grams
Ammonium Perchlorate	0.57	9.15	257.1
Magnalium, 200 mesh	0.24	3.8	107.1
Barium Sulfate	0.14	2.3	64.3
Potassium Dichromate	0.05	.75	21.5
Mineral Oil	+0.02	0.3	9

Note: The ammonium perchlorate, barium sulfate, and potassium dichromate are each milled individually in a blade-type coffee mill until they are fine enough to pass through a 100-mesh screen.

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. Wear your protective gear even when you are pressing the finished fuel in the rocket motor.

I'll be making 3/4-inch ID (one-pound) size, strobe rocket motors. Each motor will use about 39 grams of whistle fuel and 25 grams of the strobe fuel. So, the 450-gram batch of strobe fuel shown in the formula above will be enough for approximately 18 motors.

All the dry chemicals are weighed out individually, then mixed thoroughly by gently passing them through a 20-mesh screen or kitchen colander. I put this mixed powder into a small plastic bucket.

I weigh out the mineral oil into a clean quart jar, such as a spaghetti sauce jar, and then I add 1/2 cup of the Coleman Fuel to the oil. After tightly screwing the jar's lid on, I shake the liquid to completely mix the two ingredients.

This mixed liquid is then added to the dry powder, and it is completely blended in with gloved hands. The damp composition is then dried over a pot of hot water, as described in the tutorial on making whistle fuel. Once again, the fuel is never brought anywhere in the vicinity of any open flame or source of sparks.

After a couple of hours of drying over the pot of warm water, the fuel will be dry, will stop smelling of Coleman fuel, and will resemble grayish-green sand. I use my gloved hands to break up fuel clumps as it is drying.

Strobe Rocket Fuel on Kraft Paper Lined Tray

The Rocket Tooling

To make the 3/4-inch ID strobe rockets for this project, I'll be using my tooling, which is very similar to the Skylighter TL1361 tool set. Strobe rocket tooling is almost the same as whistle rocket tooling. The main difference is the spindle is about twice as long. The number of rammers ("drifts") can vary from tooling to tooling.

Skylighter One-Pound Strobe Rocket Tooling

Just as I did in the whistle rocket project, I polish the drifts and spindle using very fine sandpaper and metal polish to facilitate removal of the drifts during the pressing.

Strobe Rocket Motor Tubes

Once again, because of the high pressures used to make these engines, and the high thrust they develop, I use the extra-strong TU1066 3/4-inch ID paper tubes. For these motors I cut the tubes 6 inches long.

Cutting TU1066 Tubes into 6-Inch Long Strobe Rocket Motor Tubes

The Tube Support

A 6-inch long, PVC plumbing pipe and band clamp tube support is used to reinforce the paper tube during construction.

PVC Pipe Support for Paper Strobe-Rocket Motor Tube

Drilling the Fuse Hole

Just as I did with the whistle rocket motors, I drill a 1/8-inch hole through the side of the paper engine tube, right where the bottom of the fuel grain will be.

Drilling Fuse Hole in Strobe-Rocket Tube

Marking the Tooling Drifts for Safety

At least 1/8-inch clearance is allowed between the spindle and the point where the drifts would contact it. I mark my tool drifts with masking tape to be absolutely sure they never pinch fuel between the drift and the spindle while the fuel is being pressed. Pinched fuel can explode upon pressing. That 1/8-inch clearance is enough to prevent this.

My particular tooling set only has one hollow rammer and one solid rammer. Some tooling comes with two or three hollow drifts, and each one must be marked with tape accordingly for safety.

Strobe-Rocket Tooling Marked with Masking Tape for Safety

Pressing a Strobe-Rocket Motor

Cross Section of a Strobe-Rocket Motor

The first thing I do in this pressing process is scoop out a paper cup full of whistle fuel, and a paper cup full of strobe fuel, set them aside and put the large tubs of my fuels away in safe storage. As I've mentioned before, this is perhaps the most important safety precaution: limiting the amount of exposed flammable composition when working with it.

For my strobe rocket, I press the whistle fuel in the tube in the same way and with the same pressures I did when making the whistle rocket motors. Pressing three 7-gram increments, and one 4-gram increment of the whistle fuel brings that fuel halfway up the spindle. These increments are pressed with the hollow rammer.

I use black rubber o-rings on my rammers to keep dust down to a minimum during the pressing. These o-rings, as seen at the top of the solid drift in the photo of the tooling above, also serve another purpose.

Each time the rammer is about to be reinserted into the tube, I slide/roll the o-ring down toward the end of the rammer. Then, as I insert and press the drift down into the tube, the o-ring seals against the top of the tube and prevents much dust from blowing out. When the drift is removed after that increment, the o-ring's position marks where the top of the tube was, and just how far into the tube the drift went while pressing that increment.

When the drift is removed from the motor after an increment is pressed, the o-ring stays put on the drift exactly where the top of the motor tube was before the drift was removed.

Critical: I keep a full-scale sketch of the motor on my workbench as I'm pressing the motor. I'll put the drift, with the o-ring marking where the top of the motor tube was, down on the sketch, and keep track of how high the pressed fuel is coming in the motor. In this way I can precisely determine when the whistle fuel is pressed up to the desired level, and switch to the strobe fuel increments.

Hydraulic Pressing a Strobe-Rocket Engine

I keep the hollow rammer cleaned out as I press the fuels, because I never want to be pressing fuel up inside the rammer, between it and the spindle.

Cleaning Fuel Out of a Hollow Drift

Then I press three 7-gram increments of the strobe fuel with the hollow rammer, and one 4-gram increment of that fuel with the solid rammer, being very careful to not press past the safety-tape line on that rammer.

This brings my strobe fuel up to about 3/16-inch to 1/4-inch above the end of the spindle, as checked once again by comparing the drift and o-ring with my sketch. The final strobe fuel increment is adjusted so that it reaches that level.

This strobe-fuel distance above the spindle is critical. Too little strobe fuel will cause the motor to start its whistling delay burn too soon. Too much strobe fuel above the spindle will cause the motor to burn too long, turn back toward earth, and perhaps even return all the way to the ground before the heading bursts.

Note: Ask me sometime how I know about the effect created when too much strobe fuel is pressed above the spindle. The story deals with a six-pound strobe rocket coming back to earth, going through the roof of a meeting tent as there was a "parting of the seas" in the crowd, bouncing off a swimming pool diving board, and the heading explosion nearly scaring Doc Barr to death, or at least into regaining the memory of most of his previous sex life. Oh, I can laugh about it now, but it was damn embarrassing at the time.

After the strobe fuel has been pressed to that critical distance above the spindle, another two 7-gram increments of the whistle fuel are pressed above the strobe fuel, as shown in the sketch above. This whistle fuel section creates the whistling "delay" portion of the rocket's flight before the ignition of the header.

As I mentioned in the whistle-rocket article, other "delay" effects can be produced. Colored fuels can be used instead of the whistle delay fuel, or titanium can be added to the whistle delay fuel. The amount of delay fuel has to be dialed in to produce the desired effect and length of flight.

The motor is then capped off with a 7-gram increment of bulkhead clay, with a passfire hole hand-twist-drilled into it. I never drill into whistle fuel with titanium in it, as I warned in the whistle-rocket article.

If I do use whistle fuel containing titanium in the delay section, I cap it off with 1/8-inch of fuel with no metal in it. Then I carefully hand-twist-drill the passfire hole.

Hand-Twist-Drilling Passfire Hole through Clay Bulkhead

Troubleshooting: The various amounts of fuel, and the distance up the spindle between the two fuels, have been dialed in for my own fuels and tooling. If your pressed rocket motor blows up on the launch pad, then less whistle fuel and more strobe fuel should be used. On the other hand, if your rocket doesn't have enough power at launch, more whistle fuel and less strobe fuel should be used.

So, there we have it, a finished strobe-rocket motor. One final thing I'll do is carefully re-enlarge the fuse hole with my awl since the hole can become a bit closed down and filled with fuel during the motor's pressing.

Enlarging Fuse Hole with Sharp Awl

Creating a Rocket Header

These rockets can fly so high that I really like to only use report headers on them. The effect of a star-shell header could get lost up at that altitude. As I showed with the whistle rockets, the hollow end of the motor tube can be filled with loose whistle fuel, perhaps containing some titanium, and then capped off to create a small report heading.

Loose strobe fuel, which is also a powerful explosive, can be used in this way, too. If more hollow space is desired, the motor tube can be extended with an extra piece of the same motor tube, glued and taped onto the motor tube to extend it.

For a larger, more impressive report heading, Skylighter's PL1020 or PL1022 plastic #5 can shell casings can be used. These plastic cans measure slightly less than 2 inches in diameter, and work well on these one-pound rockets.

I fill the recess in the can's cap with hot glue, drill a quarter-inch hole in the can's bottom, and hot-glue a piece of quickmatch or fast fuse into that hole. When gluing the fuse into the can, I make sure all the gaps around the fuse are filled with glue to prevent any composition from leaking out of the can after it is filled.

The fuse will transfer fire from the top of the rocket motor to the heading.

1/4-Inch Holes Drilled in Plastic Can Bottoms, Recessed Caps Filled with Hot Glue

Hot-Glue Quickmatch into Plastic Can Bottom

Then I fill the can with my report composition of choice. The traditional filling would be flash powder, but making flash has become a bit problematic for some in the current legal climate.

If one has legal access to the necessary chemicals, I'll describe a safe way to make a flash report with one of these cans. But first, I'll detail three alternatives for making a report without flash powder.

A simple report can be made by filling the can with black-powder-coated rice hulls, with the addition of some coarse titanium if silver sparks are desired. One of the cans can hold 45 grams of the BP-coated hulls, and 14 grams of the titanium.

Plastic Shell Casing Filled with Black-Powder-Coated Rice Hulls

Two other alternatives would be to fill the can with loose whistle fuel or loose strobe fuel. A can will hold 57 grams of my whistle fuel, or 67 grams of my strobe fuel. For silver sparks, 14 grams of titanium can be added to either of these fuels by putting the fuel and the titanium into a small paper cup and gently swirling the two together to mix them before pouring them into the can.

Plastic Can Shell Casings Filled with Whistle Strobe Fuel

Note: I mention this flash report composition option out of a sense of responsibility. Folks will make flash reports. There is a long tradition of it in all kinds of fireworks. But, flash powder is the most powerful composition that fireworkers work with, and many really serious pyro accidents involve it.

Flash Report Composition

Learn How to Safely Make Flash Report Rocket Headings...

No matter which report composition I used, I then glued the caps onto the plastic casing cans with PVC plumbing cement from Home Depot. I did this outdoors because of the fumes, wiping the excess glue off with a paper towel.

I then strengthened the casings with some 1/2-inch wide fiberglass-reinforced strapping tape. Since my tape roll was 1-inch wide, I split the end of the tape in half. This allowed only one half of the width to tear off as I used it.

Note: During this taping process, the normal handling of the binary-mixed flash report is enough to sufficiently mix the ingredients. No rough shaking is necessary. Once the can is closed, handling this report is no more dangerous than the normal handling of a commercial fireworks salute.

Plastic Casings Reinforced with Strapping Tape

I then finished the headings off with a layer of aluminum foil duct tape.

Rocket Headings Finished with Aluminum Foil Tape

Here is a video of each of the four different report compositions, made as described above.

Video of Black Powder, Whistle Fuel, Strobe Fuel, and Flash Reports

Attaching a Heading, Fuse, and Stick to a Strobe-Rocket

I first trim the header fuse so that it is long enough to go all the way through to the bottom of the passfire hole, and is pressed against the rocket's fuel grain. I bare the last 3/4 inch of the fuse.

Rocket-Heading Fuse Trimmed and Bared

Then I put a bead of hot glue around the top of the motor tube and quickly install the header, carefully making sure the fuse goes all the way down into the passfire hole as I do so. I reinforce the joint between the header and the motor tube with an additional fillet of hot glue.

I've found that the slick side of a piece of the paper backing from the aluminum foil duct tape comes in handy for smoothing fillets of hot glue without burning my fingers.

Rocket Heading Hot-Glued onto Motor Tube

The joint is then reinforced with some vertical, 3-inch strips of strapping tape, finished off with horizontal bands of the tape around the heading and the motor tube. This really strengthens the connection.

A 45-inch long, 5/16-inch-square, poplar rocket stick, with a beveled end, is then hot-glued and strapping-taped to the motor. If the rocket is to be flown immediately, then a 6-inch piece of Visco fuse is inserted into the motor's fuse hole.

Final Heading Connection Reinforcement

Completed Rocket With Stick and Visco Fuse Installed

If I am going to store the motor for a while before launching it, I won't install the Visco fuse now, but will instead seal the end of the motor and the fuse hole with aluminum foil tape to prevent the whistle fuel from absorbing moisture.

Conclusion

Well, it's been a bit of a journey, but in the last 3 projects we've made whistle fuel, whistles, whistle rockets, strobe fuel, strobe rockets, and impressive report headings. While these powerful fuels and devices are not exactly beginner's projects, if they are approached one step at a time, with good safe work habits, they can indeed be some of the most impressive and satisfying fireworking devices around, both for the builder and for the audience.

Stay Green and Have Fun,
Ned

How to Make Fireworks Whistle Rockets

By Ned Gorski

What Is a Whistle Rocket?

I think a really impressive fireworks device speaks for itself, so here's a video of one of these whistling firework rockets in action.

Video of a One-Pound Fireworks Whistle Rocket

A whistle rocket does just that: whistles and screeches as it leaps skyward. The motor uses the same whistle fuel that was used in the "How to make a whistle" article. Whistling rockets are "hot." They leap off the launch pad and can really reach a seriously high altitude if they're made well.

I've made whistle rockets in sizes from 1/4-inch ID super-bottle-rockets up to 1.5-inch-ID "six-pounders."

I've lifted some big ball shells (called "headings" when they're carried by rockets) with the larger whistle rockets. But, often they fly so high that the effect of such a heading is lost. For that reason I prefer to simply put a large report heading on them with some coarse titanium in it for impressive silver sparks when the header explodes.

Other variations in construction can include various "delay" effects during the coasting portion of the flight following the initial powerful thrust portion--from simply allowing the rocket to continue whistling across the sky, to having the whistle change to a brilliant red flare or a color changing one, before the heading finishes the rocket's flight.

Be aware, though, that whistle rockets are not your "father's black-powder rockets." The rocket fuel used in these babies is powerful. If the rocket engines are not dialed in carefully and fused properly, very impressive CATO's ("bombs on a stick") can result.

Warning: Do not EVER hand-ram whistle rockets using a mallet. The fuel is sensitive and could be set off in that process. Whistle rockets must be pressed using a manual arbor press for small rockets or a hydraulic press for larger motors, which require more pressure. It is wise to use a safety shield on a press just in case something goes wrong and the motor ignites during construction.

Hydraulic Rocket-Press with Safety Shield

Whistle Rocket Fuel

I'll be using the same fuel that I specified in the article on making whistles. The alternative fuels I mentioned in that essay can be used to make whistle rocket motors. But there will be the requisite "dialing in" in order to maximize performance and consistency with those variations.

Whistle-Rocket Fuel on Paper Lined Tray

So, study that article and make some of that whistle fuel, observing all the pertinent safety precautions.

Whistle Rocket Tooling

I will be making one-pound, 3/4-inch ID, whistle rocket motors for this project. Skylighter carries TL1311 tooling used to make these engines.

Whistle Rocket Tooling

This tooling set comes with a base, a spindle, a hollow rammer for pressing the fuel increments around that spindle, and a solid rammer with which to press the increments of fuel above the spindle.

Note: You may notice the tooling I'm using in this project, which I've had for years, is different than the Skylighter tooling. But, my spindle is about the same size and the motor construction and performance are very similar.

Whistle Rocket Motor Tubes

Because of the high pressure at which the fuel is pressed in these motors, and the thrust they develop during flight, high-strength paper tubes must be used in their construction.

Skylighter TU1066 3/4-inch ID, 1/8-inch wall, extra-strong tubes are an excellent choice for these whistle rocket motors. I cut the 30-inch long tubes into 4.75-inch long tubes for these engines.

Cutting Tubes for Whistle Rocket Motors

The Tube Support

Because of the high pressure used to press these motors, the tubes would bend, split, and collapse if they were made using no tube support. A good support is absolutely essential when making these motors.

A 4.75-inch piece of 1-inch ID, PVC plumbing pipe serves well as a tube support. It is sliced lengthwise with a hacksaw to ensure that it will go around the paper tube and fit snugly when the slice is closed. The support is held tight with metal band-clamps, installed side-by side, and tightened with their screw-adjusters alternated around the circumference of the support.

PVC-Pipe Support for Whistle-Rocket Paper Motor-Tube

Polishing the Tooling

Unlike the fuels for charcoal tailed rockets, whistle rocket fuel tends to be "sticky." The high pressures used to press the fuel around the spindle cause the fuel to adhere to it. This makes the motor hard to remove from the spindle once the engine is pressed. And the sodium salicylate fuel I prefer is reportedly stickier than fuels made with potassium benzoate or sodium benzoate.

Here is a solution, though, regularly touted by master-rocketeer Steve LaDuke. Polish your tooling, especially the spindle, using very fine, 600-grit sandpaper and a good metal polish. I got an excellent polish, Mothers Billet Metal Polish, at my local auto-parts store.

Polish Whistle-Rocket Tooling with Fine Sandpaper and Metal Polish

First, if I have any scratches or small imperfections on the spindle, I remove them using a small piece of the sandpaper to smooth the tooling. Sanding in a lengthwise direction on the spindle ensures any remaining scratches run in that direction, rather than in a circumferential pattern, which would make the motor-removal more difficult.

Then, using a small section of soft rag, the tooling, including the rammers, is polished until it all has a mirror-smooth finish. This really enhances the ease of use of the rammers, and the finished rocket motor's ability to be removed from the spindle.

I even do the best I can to polish up inside the hole inside the hollow drift ("drift" is another word for "rammer"). This will help release any fuel which gets between that hollow part and the spindle during pressing.

Polishing the tooling this way is time well spent. It will help avoid a lot of aggravation in the next steps of pressing the motor and removing it from the spindle when it's done.

Pressing a Whistle-Rocket Motor

Besides being pressed in a longer tube, and on a longer spindle, a whistle-rocket motor is not much different than a regular whistle. But I do fuse whistle rocket motors differently than I fuse standard whistles.

Fireworks Whistle-Rocket Motor Cross-Section

Drilling the Fuse Hole

You'll note that the fusing technique shown in the diagram is different than most rocket fusing. There is a method to my madness.

The first thing you might notice is there is no clay nozzle in whistle rocket motors. A whistle rocket needs to have the bottom of its motor tube wide open. So the fuel has to be ignited right at its bottom edge, or else there's a good chance the motor will blow up due to over-pressurization after ignition.

It can be a challenge to install a fuse from the bottom of the motor, only touching the edge of the fuel-grain, with no nosing to hold it in place.

Some folks hot-glue the fuse to the inside surface of the paper tube. Others use masking tape to attach the fuse to the rocket stick. I've tried both of those methods. With some care they can work fine, but at other times I've had the fuse fall off as it was burning, before igniting the motor.

So, I came up with the solution of installing the fuse as shown above. Before pressing any fuel, I drill a 1/8-inch hole through the motor casing, right at the outside edge of where the fuel grain will begin. I use a piece of wooden dowel to back up the inside of the paper tube during the drilling operation.

Drilling 1/8-Inch Fuse Hole in Whistle-Rocket Motor Tube

Marking the Tooling Drifts for Safety

Next, I mark the tooling drifts with masking tape to ensure they never come into contact with the spindle when I'm pressing a motor. I allow about 1/8-inch margin of safety between the drift and the spindle when I'm applying the tape.

Marking Tool Drifts with Masking Tape for Safe Clearance

Pressing Rocket Fuel into the Tube

The hollow drift is used to press the increments of fuel, until the fuel is above the spindle. All the increments are pressed to 7500-psi (pounds per square inch) on the composition.

In the article on making whistles, I illustrated the method for determining how much hydraulic press force to use with a solid drift. Applying 2200-psi of pressure according to my press's gauge results in an actual 7500-psi on the composition with the solid drift.

But, since the hollow drift has the hole in it, less force will have to be applied to it to achieve this same pressure on the fuel.

End of Hollow Whistle-Rocket Drift

With some math, I've determined that the surface area of the end of this hollow drift is about 80% of the surface area of a solid-end drift. For this reason, when using the hollow drift I'll only apply about 80% of the force with my press that I'd apply when using the solid drift.

So, for the increments that are pressed around the spindle with the hollow drift, I'll press up to a gauge reading of 1750-psi on my hydraulic press.

The first thing I do when pressing a motor is remove a small paper cup of the fuel from the tub of fuel. Then I close the tub tightly and set it aside away from where I am working. That way, only the small cup of fuel is exposed in case something goes wrong.

Ready to Load Whistle Fuel into Rocket Motor Tube

With the support securely fastened around the paper tube, and with the fuse-hole-drilled end of the tube mounted on the spindle, I introduce 7 grams (1/4-ounce) of the whistle fuel, using a funnel.

Weighing Whistle Rocket Fuel

I then consolidate that fuel increment with the press in two steps, by first pressing up to only 1000-psi on the gauge.

I remove the drift and use the smooth, round end of my awl to clean any fuel that is wedged in there out of its hole. Then, I insert the drift back into the tube and press the rest of the way up to 1750-psi on the gauge.

Cleaning Whistle Fuel Out of Hollow Drift

If I press all the way up to the full pressure on the hollow drift in one step, fuel will work its way up between the drift and the tube, and between the spindle and the drift, in its hole. This can bind the drift in the motor, which makes it difficult to remove after the increment is pressed. Pressing the increment in two stages, and cleaning the drift between those two pressings usually eliminates stuck-drift syndrome.

When I'm pressing a really large motor, such as a 1.5-inch ID model, I'll actually press each increment in 3 or 4 stages to reach the full pressure in order to keep the drifts from getting stuck.

Pressing a Whistle-Rocket Engine in a Hydraulic Press

Four, 7-gram increments of the fuel, pressed in this manner with the hollow drift, bring the fuel to just above the spindle, using my fuel and tooling. This can vary a little from batch to batch of the fuel, or with different tooling.

After the fuel is above the spindle, I switch to the solid drift. Now I press the same 7-gram size increments in one pass up to the full 2200-psi reading on my gauge.

For the rocket shown in the initial video in this article, I press fuel to one inch above the spindle. That requires three 7-gram increments with the solid drift, for a total of 49 grams of fuel in this motor.

I cap the motor off with a 7-gram increment of bulkhead clay mix.

Adjusting the Total Flight Time of the Whistle Rocket

The portion of the rocket's flight after the initial high-thrust phase, and before the heading bursts, is called the delay section of the flight.

The fuel around the circumference of the spindle, and above it for that same distance, about 1/4-inch, burns very rapidly in the highly pressurized thrust period of the rocket motor's burn.

Whistle Rocket Motor's Thrust Fuel and Delay Fuel Sections

Then, the solid portion of the fuel above that thrust fuel burns more slowly in a less pressurized environment. That's why the whistle sound changes so drastically after the initial thrust burn.

So, in this rocket motor I had 1/4-inch of thrust fuel above the spindle, and then about 3/4-inch of delay fuel above that. If I shorten that delay fuel, the delay portion of the flight would be shorter. If I lengthen the delay fuel column in the motor, that delay portion of the flight would be longer.

Looking at the video at the beginning of this article, the one-inch of total fuel above the spindle produced that particular flight and delay before the heading exploded. I was pretty happy with that rocket's flight. I might have lengthened the delay fuel column another 1/4-inch to see if that produced a more pleasing flight in the next rocket.

Other interesting modifications can be made to the delay fuel grain. Once the fuel has been pressed to above the spindle, spherical titanium can be added to the fuel increments that get pressed with the solid drift. The delay fuel is weighed into a paper cup. I add 10% of that fuel's weight in titanium. Then the cup is swirled to mix the components.

The titanium fuel mix is pressed one increment at a time, the same as described above. The metal will produce a silver spark trail as the delay-fuel burns. If the hard metal is added to all the fuel (below the top of the spindle), it will tear the spindle up pretty quickly. Since it also might pose a sparking threat, I only add it to the delay fuel.

If I plan to have a passfire hole, I usually drill the hole down through the center of the clay bulkhead into the fuel. But, I don't want to drill into any fuel containing titanium; so I'll cap any titanium-fuel off with 1/8-inch of plain fuel (no titanium in it). Hand-twist-drilling into that is safer.

The effects you can create using the delay fuel are limited only by your imagination. For instance, in his article "How to Make Fireworks Rockets with Green and Red Tails," Dave Stoddard describes delay fuels used to change the rocket tail's color to a green or red flare as it flies upward.

Removing the Tube-Support from the Tube, and the Motor from the Spindle

After the fuel and clay have been pressed in the tube, it's time to remove the motor from the spindle. This is easier if the support is removed from the engine first, which loosens the motor on the spindle just a tad.

First, I loosen and remove the metal band-clamps from the support, and then slide the PVC support off of the motor.

Then the motor is twisted off the spindle. Putting the spindle base in a vise or holding it rigidly in the rocket press can facilitate this. Using both hands to twist it, the motor is carefully removed from the tooling. Do not use clamps or pliers on the motor itself, or you will risk cracking the fuel grain, which will cause the rocket to explode instead of fly.

Support Removed from Tube, Whistle Motor Removed from Spindle

Drilling Passfire Hole into Clay Bulkhead

If I am going to put a heading on the rocket, then I'll need a passfire hole in the clay bulkhead to transfer fire from the last of the rocket fuel to the heading.

I create this passfire hole by carefully hand-twisting a drill bit into the center of the bulkhead just through the clay into the pink fuel. (Remember that the last 1/8-inch of fuel that was pressed should contain no titanium, even if titanium was added to the rest of the delay fuel.)

Warning: Never use a power drill to create the passfire hole. The friction and heat caused by such fast drilling could ignite the motor. Only use hand twisting on the drill bit to create the hole.

I've found that starting the hole with a sharp 1/8-inch drill bit, hand twisted through the clay until it just barely penetrates the fuel, works well. Then I'll expand the hole with a 1/4-inch diameter bit to widen and create the final passfire hole.

Hand-Twist Drilling a Passfire Hole through Clay Bulkhead

Simple Rocket Headers

Several types of simple headers can now be employed on this whistle rocket.

There is a 1-inch long empty space in the motor tube above the drilled clay bulkhead. First of all I like to insert a couple of pieces of black match, from either quickmatch or fast-fuse, into the drilled bulkhead passfire hole. I cut these pieces of match about 1.5-inches long so they reach the bottom of the passfire hole, and extend just to the end of the motor-tube.

Inserting Blackmatch into Whistle Rocket Passfire Hole

These strands of blackmatch ensure positive fire transfer from the last of the rocket-fuel to the header.

For a spray of stars at the end of the rocket's flight, a small amount of black powder can be put into the tube's recess, followed by some of the stars.

For a falling glitter comet, some of the black powder followed by a single 3/4-inch comet can be used to fill the end of the motor.

For a small report at the end of the rocket's flight, the end of the tube can be filled with either loose black powder or loose whistle fuel. A pinch of coarse titanium can be added to either of these powders to produce silver sparks when the header fires.

End of Whistle Rocket Motor Filled with Loose Whistle Fuel

With any of these types of headings, the motor is then capped with a 1-inch end disk, glued on.

If a report heading has been made, I like to reinforce the report tube-section and end cap with some strapping tape, finished off with some peel-and-stick aluminum-foil duct tape. This reinforcement really helps a report heading to "pop."

For a star or comet heading, simply gluing a paper disk on is sufficient to finish the end of the motor.

Finishing Rocket Report Heading with Strapping and Aluminum Tapes

Installing Rocket Stick

The last step to finishing this rocket is to install the stick. I'm using a square poplar stick that I ripped on my table saw. It measures 5/16-inch square by 36-inches long. I bevel the end of the stick, hot-glue it straight on the motor, and finish the attachment with two bands of strapping tape. I make sure the stick does not cover the fuse-hole.

Attaching Stabilizing Stick to Whistle Rocket Motor

A 6-inch piece of Visco fuse can now be inserted into the fuse hole, and the rocket is ready to be placed in a launch tube and flown.

Visco-Fused Whistle Rocket Loaded in Launch Tube

Sealing the Rocket Motor for Storage

If I'm going to store the finished rocket for a while, I like to seal the bottom of the motor and the fuse-hole with some aluminum-foil duct tape. This prevents the hygroscopic rocket fuel from absorbing atmospheric moisture during storage, and protects the motor from flame or sparks until flight-time.

Sealing Bottom of Rocket Motor and Fuse-Hole with Aluminum-Foil Tape

Prior to flight, the tape is completely removed from the motor's bottom, and the Visco fuse is installed through the fuse hole.

Motors without sticks can be stored in sealed plastic baggies along with a bag of desiccant to ensure they do not absorb moisture.

Conclusion

Well, there you have it--one of the most interesting and powerful rockets you can make.

Next time I'll show you a nice variation on this basic motor, the strobe rocket, and some different ways to create a rocket heading.

See ya then,
Ned

How to Make Pyrotechnic Whistle Mix

To Whistle or Not to Whistle?

This is the first of three related projects that Ned is creating for you on how to make whistling fireworks. I want to preface them by saying one thing:

If you want to make whistles, this article can save your life!
Look, I think most of us build fireworks because we want to have fun. And whistles, when you see and hear them, are definitely awesome. But this is one area of fireworks making that, if it goes wrong, will definitely take the fun out of fireworks for you, and quite possibly for others in your life as well.

So, to anyone who has ever aspired to making a whistling rocket, or any other sort of fireworks whistle, read this fireworks-making project twice before starting.

Why You Should NOT Try to Make Whistling Fireworks

Whistles are DANGEROUS. Whistle mix is highly explosive, and sensitive to just about everything you could inadvertently do: too much pressure, too much impact, or any friction, sparks or static electricity. Screw up and you'll have a catastrophic explosion and possibly injure or even kill yourself.

Accidental Whistle Explosion

Photo Courtesy Jerry Durand

Making whistles means equipment. You need a press and special tooling to start with. This can cost money and takes space. Don't take this on, unless you're ready to make the necessary investment in the kinds of good equipment that Ned shows you how to use in this project. Believe me, you cannot cut corners when making whistles: either you invest in the right equipment and learning, or you fail, possibly catastrophically.

Making whistle fireworks is not instant gratification. Whistle fuel takes time to make. And you have to be extraordinarily careful, and you cannot rush it.

Why You Might Want to Learn to Make Whistles

Making a big whistling firework and using it in a fireworks display is a guaranteed crowd pleaser. It is something most of them will never have seen and heard before. This is a firework the big boys make and that audiences just love.

The satisfaction you can get from adding whistles to your aerial shells, or launching your first whistle and strobe rocket, is mind altering. It will pump you up like few other fireworks can.

Within this and the next two projects, you have what I consider to be the best tutorials ever written on making whistles and whistling fireworks (rockets, fountains, etc.). That means, that if you follow Ned's instructions closely, you can pretty much be guaranteed of successfully making just about any kind of whistling firework you can imagine. It’s an opportunity to learn something that only pyrotechnic experts know how to do. And to do it well.

Harry Gilliam
Chief Cook & Bottle Washer

How to Make a Whistle

By Ned Gorski

What are Fireworks Whistles?

Often when making fireworks we focus on visual effects. But our ears can detect a lot of other effects that are going on. The special sound of a charcoal, core-burning rocket as it quickly "Whooshes" out of the launch tube is quite different than the slow "Shhhhhhhh" as an end-burner launches, and I enjoy the sound of them both.

For the Pyrotechnics Guild International's convention I have made girandolas containing multitudes of these core-burning motors, and I eagerly look forward to hearing them as they rise skyward. It's a bit like a jet engine taking off.

For a different sound, I have some girandolas, which have whistle motors on them, and I also have some of these whistlers on my competition Chromatrope wheel. Whistles add one more auditory dimension to fireworks effects, and while Saturn Missiles can wear thin on me after a while, I do enjoy a whistling effect occasionally.

Video of a Horizontal Wheel Driven by Two Whistles, Half Plain Whistle Composition, Half with Titanium Added

So what, then, is a whistle? For the purposes of this article it is a pyrotechnic device designed to produce a shrill audible effect. But there are whistles and there are whistles. There are two primary types, and you need to know the difference before you make them, so that you can pick the correct tooling.

There are whistles designed to generate powerful thrust in order to fly, and whistles, which have lower thrust. Whistles with high thrust are normally used as whistle rockets. Low-thrust (or simple) whistles are used to add a sound effect to a firework device and/or as drivers to turn wheels. Both types emit showers of sparks.

Note: To make any kind of whistle, you must use a press (either hydraulic or arbor) and tooling that is specially designed to make whistles. The important thing to remember is that you use different types of tools for different kinds of whistles. Simply put, there is whistle rocket tooling, and there is simple whistle tooling. Be sure you have the correct tooling before you start.

Warning: Attempting to make whistles without the proper tooling can be fatal. Whistle composition is highly impact and friction-sensitive, and is a very powerful explosive.

Whistle rockets have a sound all their own, and can be flown with only the whistle engine, or with other pyrotechnic effects, such as strobes, shells, or salutes.

A simple row of stand-alone whistles, mounted like fountains on the ground, will certainly grab an audience's attention during a fireworks display.

Whistles can also be loaded into an aerial shell, such as a color-whistle-and-report shell. When the whistles have a bit of titanium in them, they make wonderful silver-tailed whistling inserts. If they are used as shell inserts, only the amount of fuel that will burn for 4-5 seconds is pressed in them so that they don't burn all the way to the ground.

Whistles can also be mounted on the exterior of an aerial fireworks shell, ignited when the shell is launched out of the mortar, and serving as a whistling rising-effect as the shell rises skyward.

Making whistle fuel and pressing simple whistles are two of the first steps to making whistle rockets and strobe rockets, which I'll be exploring in follow-up articles. That means the skills I'm about to describe are building blocks for further, more advanced projects.

What Makes A Fireworks Whistle Whistle?

Honestly, the precise answer to that is a bit beyond the scope of my expertise. Rather than it being a result of gasses passing through a tube and across an opening, as in a musical instrument or a simple "coach's whistle," pyrotechnic whistles produce their sound through a rapid, oscillating burning, which produces the sound.

There, that's as much as I know about that. But I do know that if I follow the next procedures, I'll end up with a device that whistles.

How to Make Whistle Mix

Warning: Whistle fuel is powerfully explosive stuff, roughly equivalent in power to that of flash powder. Much care must be exercised when making and using it. You'll notice that in the method I'm about to describe, the fuel is never mixed in a dry state. Some parts of it are mixed together; then that mixture is dampened with a wet solution. Only then is the remaining dry ingredient added. This greatly reduces the risk of unwanted ignition due to static or friction.

Fireworks Tips #45 contains Dan McMurray's article, "Whistle Rocket Fuel in Under 8 Hours." I have always made my whistle fuel based on the recommendations in that essay, but have slightly modified it for my purposes. I'd recommend that readers familiarize themselves with that method before proceeding.

Especially, please study all the safety recommendations contained in Dan's article. I'm not going to repeat them all here. I strongly suggest that you familiarize yourself with them before proceeding with the following steps.

Making whistles is very similar to making gerbs, and I'd recommend a familiarization with that process, as well.

I'm about to make whistles using a common formula, which contains sodium salicylate as the fuel and red iron oxide as the catalyst. There are other fuels such as sodium benzoate and potassium benzoate, which can be used to make whistles. The list of alternative catalysts is almost endless.

My friend, Danny Creagan, has done extensive research using these alternative fuels and catalysts, and has tabulated his results, and you can see his whistle mix data here.

I highly recommend a look at this information for anyone interested in achieving different power or sound with their whistles by varying the fuel and/or catalyst in the mixture. I suggest you pay particular attention to the video of the whistle composition explosion there.

The first thing I do when making whistle fuel is get a large stainless steel pot of water boiling. This pot of hot water will be used to dry the whistle mix. I never get whistle mix anywhere near the burner that I use to heat the water.

Boiling Water for Drying Whistle Fuel

I use a slightly modified version of Dan's formula for whistle mix. This formula is slightly less energetic, and mineral oil is used instead of Vaseline. So the formula I use is:

Whistle Mix Fuel

Chemical	%	64 ounce batch	1800 grams
Potassium Perchlorate	0.66	42.25 ounces	1188 grams
Sodium Salicylate	0.29	18.55 ounces	522 grams
Red Iron Oxide	0.01	0.65 ounces	18 grams
Mineral Oil	0.04	2.55 ounces	72 grams
Total	1.00	64 ounces	1800 grams

Note: I use the mineral oil instead of Dan Murray's Vaseline, because it does not have to be melted before mixing it with the Coleman fuel. I use this slightly "toned-down" formula because I find it to be a little more forgiving, resulting in fewer "CATO's" (blown up devices).

The potassium perchlorate is a very fine powder, capable of falling easily through a 100-mesh screen. Screening it through a 40-mesh screen breaks up any clumps in it.

The sodium salicylate and iron oxide are mixed together by screening through a 20-mesh, kitchen colander screen. Be sure and use the 20-mesh screen; the sodium salicylate will not pass through a finer mesh screen. These two mixed chemicals are placed in a stainless steel pot, which is a bit smaller than the one that contains the hot water.

The mineral oil is placed in a one-quart jar, like a clean spaghetti sauce jar, and the jar is filled the rest of the way with Coleman Camping Fuel. VM&P Naphtha, which is available in the paint department of Home Depot, may also be used, as described in Dan's article.

I get my Coleman Fuel in the camping department of my local sporting goods store. The mineral oil can be found in the health-and-beauty section of a grocery store or pharmacy. The oil's label indicates it can be used as a "lubricant or laxative."

Coleman Fuel and Mineral Oil Used to Make Whistle Mix

I shake the fluid mixture a bit after putting the lid on the jar, and then the liquid is added to the sodium-salicylate/iron-oxide mixture. That composition is then stirred with gloved hands until it is a thoroughly dampened, homogenous mixture. I add just enough Coleman fuel so that the mixture is about the consistency of spaghetti sauce.

The screened potassium perchlorate is then added to the dampened mixture and more kneading is done until I have a thoroughly mixed, red composition. More Coleman Fuel may be added as necessary in order to produce a putty-like consistency, similar to soft bread dough.

All of this has been done in the smaller stainless steel pot, and that pot is now placed in the larger pot of hot water, after the burner has been turned off and the pot of hot water has been relocated to an area away from the burner. I absolutely never want to get the whistle fuel anywhere in the vicinity of an open flame.

Every step of this procedure is carried on outdoors, of course.

Pot Containing Whistle Mix Drying in Hot-Water Bath

Every hour or so, as the fuel is drying, I stir the whistle composition with gloved hands to break it up and stir it around so that it dries throughout. Then after a few hours when it is almost completely dry, I screen the mixture through a 12-mesh kitchen colander, carefully pushing it through with my gloved hands.

I put it back in the pot to complete the drying, and then pour it out onto kraft-paper lined trays for additional drying overnight.

Screened Whistle Mix Drying on Kraft-Paper Lined Tray

Sodium salicylate, like most sodium compounds, is very hygroscopic--it will absorb moisture out of the air. Because of that, I store my dry fuel in a tightly sealed bucket with a bag of desiccant in with it to keep it dry.

The whistle mix shown above is a bit desensitized by the oil in it, but it is still a powerful explosive and those of us who work with it treat it with a large amount of respect.

Pressing a Fireworks Whistle

On my wheels and girandolas I like to use whistles pressed into 3/4-inch ID parallel tubes, 3.75-inches long. These little devices make quite a racket and will burn for up to 15 seconds, depending on how much composition is pressed into the tube.

Cross-Section of a Fireworks Whistle

You'll notice I said, "pressed." Whistle mix is never rammed (pounded by hand with a mallet). It is shock sensitive and is liable to explode if rammed. Pressing whistles with a hydraulic press is much safer, but I still employ a safety shield on my homemade press.

Because of the high pressures necessary to consolidate whistle fuel, I use only Skylighter's TU1066 extra-strong-wall paper tubes. The inner layers of paper of a standard tube would crush outwards under the force necessary to press whistles. I cut these tubes to length, and use Skylighter's TL1270 Whistle Tooling.

Some kind of tube support must be used to reinforce paper tubes during the pressing operation. Otherwise the tube would burst under the pressure while the fuel is being pressed. Several types are shown below.

For instance, I use an aluminum "clamshell" support like this one.

Clamshell Support for Pressing Whistle in Paper Tubes

But a piece of 1-inch ID PVC pipe can also be used as a tube support. The pipe is split lengthwise with a hacksaw, and enough of a lengthwise slice of the pipe is removed to allow it to fit snugly on the paper tube. Metal band clamps are installed, side-by-side, on the support and tightened to create a very sturdy tube support.

Tube Support Made from PVC Pipe and Band-Clamps

A friend of mine, Dan T, uses double-walled PVC pipe tube supports. In this case a 1.25-inch ID piece of pipe would be split to fit snugly on the piece of 1-inch ID pipe, and then the clamps installed. This would create an extremely sturdy support.

Next, I carefully lay out my tooling and put a piece of masking tape on my drift so that it never comes into contact with the spindle, which could pinch whistle composition between the two and cause it to ignite.

Preparing Tooling to Make Whistles

The white PVC pipe tube-extension shown in the photo above is used to temporarily increase the length of the paper tube, which makes it easier to introduce and press the final fuel increments and the clay bulkhead, as described below.

I only use the solid rammer, which came with my whistle tooling. But, I am extremely careful to avoid any contact between it and the tip of the spindle, as I mentioned above. I can't overemphasize that point. Notice the 1/8-inch gap between the tip of the spindle and the end of the rammer in the photo above. The location of the tape ensures the rammer never gets any closer to the spindle than that 1/8-inch margin of safety.

Whistles and whistle rockets do not use a clay nozzle, as black powder rockets do. Whistle fuel burns so quickly that a clay nozzle would over-pressurize the tube and cause the device to explode.

The first thing I do prior to pressing any fuel is weigh out abut 2 ounces of the whistle mixture in a paper cup to work out of. I then tightly seal my larger container of whistle fuel and set it in a safe place, away from my immediate work area to minimize exposure of whistle composition during the pressing. This reduces the amount of explosive material near me in the event of an accidental ignition of any kind. This is the best way to avoid a serious accident.

I introduce a heaping tablespoonful (15 grams) of the whistle fuel into the tube through a funnel, and press it to 7500 psi (on the composition--2200 psi on my press's gauge. To understand the difference, see below). All the while I keep an eye on the masking tape marker to make sure the drift does not press into the tube so far that it would hit the spindle. If necessary I add a bit more fuel to this first increment before pressing it to the full pressure, to ensure that the drift never gets closer than 1/8-inch to the spindle.

Note when pressing this first increment of fuel: It's a larger quantity than the following ones, so that it can completely cover the spindle. But with this much fuel, the drift can get jammed in the motor, which is caused by too much fuel powder wedging itself between the drift and the tube wall. To prevent this, first press up to about 1000 psi on the gauge on the press. Then, remove the drift, and then reinsert it. Finish this first increment by pressing the rest of the way up to the 2200 press-gauge psi.

Note: Before pressing, you need to know something: the psi showing on the gauge is not the same as the actual psi being applied to the material in the tube. Without boring you with the reason for this seemingly nonsensical fact, here's what you have to do to convert the gauge reading to the actual 7500-psi (pounds per square inch) I want on my fuel.

The end of my drift is 0.75-inch in diameter, so it has a radius of half the diameter, 0.375-inch. The area of the end of the drift is determined with the formula: Pi (3.1416) x radius², or 3.1416 x 0.375 x 0.375 = 0.44 square inch.

There is a number of pounds of force, X, that I need to apply to that 0.44 square inch of area to achieve 7500 pounds per square inch. X divided by 0.44 square inches = 7500 psi. Multiplying both sides by 0.44 solves for X, and X = 3300 pounds of force. If I put 3300 pounds on 0.44 square inches, I achieve a 7500 pounds-per-square-inch pressure.

As I stated in the article about building my press, the reading on its gauge must be multiplied by 1.5 to determine the actual number of pounds of force it is exerting. Dividing my desired 3300 pounds by 1.5 yields the reading I want on the press's gauge when pressing these whistles, or 2200 psi on the gauge.

So, I simply press each increment of whistle fuel to this 2200 psi reading on the press's gauge to achieve the actual 7500-psi pressure on the fuel grain.

Note: All of this ciphering is something that can sound a bit like "Greek to me" until one does it a few times and gets the gut feeling for what is being determined by the calculations. Don't be put off by it. You'll get it if you haven't already.

After the initial fuel increment is pressed, further increments of flat 1/2-tablespoonfuls (6 grams) are pressed until there is about 3/4-inch of empty space left in the tube. This takes a total of about 1.8 ounces (52 grams) of composition. I then press a bulkhead of 1/2 tablespoonful (8 grams) of bulkhead clay to finish the whistle. Except for the first one, each fuel increment and the clay bulkhead end up being about 3/8-inch thick (half a tube ID) after pressing.

Pressing a Whistle Using Hydraulic Press

Note: Photo taken without safety shield installed, for clarity.

Sometimes I want titanium sparks in the spray from a whistle. If that's the case, I'll press the initial 15-gram increment without titanium in it to reduce the chance of sparks or damage to the tooling. I don't want that hard metal being pressed against my steel spindle.

Then I mix 4 grams of spherical titanium into 35 grams of the whistle fuel, simply swirling the metal and fuel together in a paper cup, and press the remaining increments of fuel.

If I am going to hand-twist-drill through the bulkhead to create a passfire, as when a whistle driver is to pass fire to another driver, I'll finish the pressing of the whistle mix with some whistle composition which has no titanium in it. I don't want to hit titanium with the hand-twisted drill bit when drilling the passfire hole.

Even hand-twist-drilling into whistle composition is not something to be taken lightly; it is something that should be done lightly, and slowly with the utmost care.

Thrust End of Completed Pyrotechnic Whistle

Whistles take fire very easily, and do not require any priming. Nosing with kraft paper and fusing with Visco-fuse or quickmatch gets the whistle ready to perform its duties.

Horizontal Whistle Driver Mounted on a Girandola

Results

Here is a video of a whistle which had only plain fuel pressed in it. It burned for almost exactly 15 seconds.

Whistle with Plain Fuel

And, here's a video of a stationary whistle that had fine spherical titanium in all but the first 15 grams of the fuel.

Whistle with Titanium Fuel

Finally, here's a video of a 24-inch diameter girandola I flew at the 2007 PGI convention, which uses whistle drivers. Thanks to Steve Majdali for the video.

24 Inch Girandol at PGI 2007

Next, I'll be following up on this article with rocket projects, which use this whistle fuel and technique to create very unique and impressive effects.

Stay tuned,
Ned

Weighing and Screening Pyrotechnic Chemicals

Introduction

Weighing out specific amounts of chemicals, and screening them together to form a composition, are the most basic firework making procedures. But, as with any skill required when making your own fireworks, these fundamental jobs can be done well or poorly, which will affect the final results of our efforts.

Indeed, weighing and screening are often the most time-consuming parts of making homemade fireworks. So, the faster and more efficiently you can learn to do these tasks, the more quickly you will be able to make fireworks.

Let's say that I want to make the Silver Titanium Fountain Fuel that was one of the compositions I made gerbs with in Fireworks Tips #108. This is one of my favorite fountain formulations and it is a simple one to start off with.

Silver Titanium Gerb/Fountain Fuel

Component	Percent	16-Ounce Batch	450-Gram Batch
Potassium Nitrate	0.51	8.15 ounces	229.5 grams
Sulfur	0.10	1.6 ounces	45 grams
Airfloat Charcoal	0.09	1.45 ounces	40.5 grams
Spherical Titanium	0.30	4.8 ounces	135 grams

The original formula gives me the percentages of each firework chemical. Then I pick a batch size that is suited for the project I'm working on. In this case, I want to make five of the 3/4-inch ID fireworks fountains I described in that gerb article. Each fountain will use about 3 ounces of the fuel, or about 85 grams (approximately 28.4 grams in an ounce).

So, I settled on the 16-ounce/450-gram batch size. I multiplied the percentage of each component times the total batch size to determine how much of each chemical to use. For example, 0.51, the potassium nitrate percentage, times 16 ounces, equals 8.16 ounces. I always round these ounce amounts off to the nearest 0.05-ounce, so the 8.16 ounces becomes 8.15 ounces.

Similarly, if I'm going to be working in grams, 0.51 times 450 grams equals 229.5 grams. I round gram measurements to the nearest 0.5 grams, so this result does not have to be rounded.

Once I have calculated the individual amounts of each fireworks chemical in that size batch, I add them up to make sure they do indeed total up to the desired batch size, and to verify that I didn't make some mathematical error in my calculations.

Now I have the weights of each individual chemical I'll be using in the project. I print that page out to have it before me as I'm performing the next steps.

Digital Electronic Scales

I have two electronic digital scales I use only for weighing chemicals used in fireworks, one for large batches of more than a few ounces, and one for small batches of only a few ounces. I got these from my favorite fireworks-supply house.

Skylighter TL5020 and TL5030 Digital Scales for Weighing Fireworks Compositions

The TL5030 scale will weigh up to 15-pounds/7000-grams with a precision of 0.05-ounce/1-gram. The TL5020 pocket scale will weigh up to 222-grams/7.8-ounces with a precision of 0.1gram/0.01 ounce. Both scales can be switched back and forth between ounces and grams.

Some pyros use mechanical, triple-beam scales to weigh firework chemicals. I've never done that, having started out with electronic, digital scales, and stuck with them ever since. Digital scales are faster to use; they give you an instant readout. You don't have to twiddle your thumbs waiting for that annoying beam to finally stop swinging up and down.

But, the electronic scales can go bad now and then. It is hard to tell when they have done so, since quite often they simply start to become inaccurate as they weigh stuff.

For this reason, I keep five quarters (US 25-cent pieces), which weigh exactly 1-ounce/28.5-grams, in a little plastic baggie in my shop. Before I weigh out the chemicals in a fireworks composition, I weigh my test-quarters to make sure the scale is still functioning accurately.

Testing the Accuracy of Digital Scales, Using Five 25-Cent Pieces

Weighing out individual chemicals for fireworks

First, I get out the tubs of the 4 individual chemicals I'll be using, and place those containers on my workbench.

I leave the titanium off to the side for now, because I do not put metals through my screens while I'm screening and mixing compositions. Fine metal particles can get lodged in the screen openings and be very difficult to remove, permanently clogging the screen, and possibly contaminating other compositions in the future. I'll add the metal to the composition later.

I store my fireworks-making supplies in their original containers, inside the inner plastic baggies, with the bags twist-tied closed, and the lids on securely. This helps prevent the chemicals from absorbing moisture from the air over time.

I also keep a dedicated, disposable, paper cup in each firework-supplies container, with which to scoop out that chemical. This is a very good way to prevent cross-contamination of one's chemicals. I like to keep my chemicals as pure as possible.

If I were to ladle out sulfur with a scoop, put that sulfur in my weighing container, and then remove some potassium nitrate with the same scoop, I have introduced sulfur into my potassium nitrate. The next time I use the nitrate, I may be using it in a composition in which I do not want sulfur; but there will be some residual sulfur in the tub regardless of my best intentions. That's not good.

Unsealed Container of Fireworks Chemical, with Dedicated Powder Scoop

If the chemicals are being weighed out for a batch, which will be going into the ball-mill, where they will be pulverized, I don't worry about the individual powders being finely screened prior to weighing them.

But, in cases such as this fountain formula, where I'll simply be mixing the components together, and I want the individual chemicals to be finely pulverized, I screen those individual chemicals through a 100-mesh screen before weighing them. If they will not pass that screen, I pulverize them individually with the coffee-mill.

Once all the individual chemicals will pass the 100-mesh screen, it's time to weigh them for my fountain-fuel batch. My large digital scale came with a nice bin to weigh powders into. I place that on the scale, and tare the scale so that the weight of the bin is not included in the displayed weight. Taring the scale simply requires placing the bin on the scale and pushing the "tare" button, which resets the scale's readout to zero. This way, only the chemical placed in the bin is weighed on the readout.

Next to the scale, I place the plastic tub into which I'll be pouring the ingredients, after I weigh them. I could weigh one chemical at a time into the main scale-bin; and just tare the scale between chemicals.

But sooner or later (probably sooner) this will cause a problem: Too often, more chemical than I really want will pour out of my chemical scoop. If I am adding that chemical onto a previously weighed one, then I have to try to remove the excess second chemical without picking up any of the first one. This becomes a royal pain-in-the-butt and slows the process.

So, one chemical at a time is weighed out, then poured from the scale's bin into the mixing tub. As I said, I'm saving the titanium for the last step, so I don't weigh it now.

Digital Scale, Weighing Bin, and Mixing Tub

As a final double-check, I pour all the ingredients back into the weighing bin after they have been weighed individually and placed in the mixing tub. I see if the total weight is what I intended it to be: in this case, 11.2 ounces of the potassium-nitrate/charcoal/sulfur mixture.

This final quality-control check ensures that I have not forgotten any chemical, which is easy to do in formulas containing many ingredients. It also verifies I weighed each individual chemical correctly. This step can save many problems down the line.

Screen-mixing the chemicals

I know my chemicals all passed the 100-mesh screen individually, so after they have been weighed, I use the 40-mesh screen for mixing them together. All of the screening and mixing is done outdoors because highly flammable dust will be created that I do not want to accumulate on my workshop surfaces.

Even working outdoors, I also wear a good dust-proof respirator and rubber gloves. Cotton clothing and eye protection are also musts. Long sleeve cotton shirts, and long cotton pants save lives every year. In a flash fire resulting from accidental ignition of mixed fireworks chemicals, the cotton may singe, but will not catch fire. Synthetics, on the other hand, will melt onto the skin in a fire.

I tear two pieces of kraft paper, slightly larger than my screen, off of my roll and place them, one on top of the other, under my screen. There are various on-line sources, such as www.uline.com or www.papermart.com for kraft paper and pull-and-tear dispensers for paper rolls.

40-Mesh Screen Sitting On Two Sheets of Kraft Paper

The batch is gently poured from the mixing tub onto the center of the screen. Then I gently rub the composition through the screen, back and forth with my gloved hands, until all of it has passed through the screen.

The screen is picked up and set aside for a moment. The edges of the top sheet of paper are raised slightly to "roll" the composition towards its center, and that paper is picked up, too. The screen is placed on the remaining sheet of paper, and the composition is poured back onto the screen from the paper, which contains it.

The comp is rubbed through the screen a second time; the screen is set aside; and the sheet of paper containing the composition is picked up. The empty sheet of paper is placed on the workbench, and the screen is placed on it. The composition is screened for the third and final time, after which it is poured back into the mixing tub.

Screening the powder three times like this breaks up any clumps of the individual chemicals and intimately mixes them together into a homogeneous mixture.

I simply bundle up the sheets of paper, which were used for the screening and dispose of them in my burn pile.

The spherical titanium is now weighed out on the scale, and that metal is added to the mixing tub. The lid is securely installed on the bucket and the metal is incorporated into the composition by gently shaking the tub.

The composition is now ready for the next steps in the manufacture of the fountains.

Uses for screens in fireworks making

The framed screens we use in making fireworks can serve different purposes. These screens are typically specified in mesh-sizes. The mesh size refers to the number of wires there are in the screen, running one direction, per inch. So a 100-mesh screen has 100 wires running one direction per inch, and 100 wires running the other way per inch. That's some mighty fine wire.

I just described above how the 100-mesh screen is used to make sure chemicals are pulverized down to at least a particular small size before mixing them.

The screens are then used in the intimate mixing of the chemicals into a formulation as I did with the 40-mesh screen.

Screens can also be used to size particles so that only that size is used in a composition. Charcoal can be specified in a range of mesh sizes, for example: 20 mesh, 36 mesh, 80 mesh, and airfloat. These different particle sizes serve different purposes in a charcoal composition.

Now, if I buy these charcoals from a firework-supply outlet such as Skylighter, I don't have to worry about separating the different mesh sizes. I'll get tubs of each individual mesh size, already sorted. But if I make and crush my own charcoal instead of some place that sells firework-making supplies, I'll have to have a way to separate, say, 80 mesh charcoal from 36 mesh charcoal from airfloat charcoal, if I want to use those particular mesh sizes, say, in a one-pound black-powder rocket fuel.

This is done by crushing my homemade charcoal and screening those crushed bits through various size screens to separate the specific sizes of particles.

If I have screens in various sizes, 10-mesh, 20-mesh, 40-mesh, 60-mesh, and 100-mesh, I can use them to sort out the various size charcoal particles.

I'll place my crushed charcoal on the 10 mesh screen and rub it on the screen. What falls through the screen is finer than 10 mesh, and what sits on the screen is coarser and will be set aside for more crushing.

I'll then put the charcoal, that passed the 10-mesh, on the 20-mesh screen and rub it with gloved hands. What won't pass the 20-mesh is sized between 10 and 20 mesh and is set aside.

What passes the 20-mesh is placed on the 40-mesh and rubbed again. What sits on the 40-mesh is sized between 20 and 40-mesh and is set aside. I keep doing this right down through my screens until what passes the 100-mesh screen would be considered airfloat charcoal, and might be ball-milled to ensure that it is as fine as possible.

So, I've ended up with charcoal in assorted particle sizes:

• Larger than 10 mesh to be crushed more
• 10-20 mesh
• 20-40 mesh
• 40-60 mesh
• 60-100 mesh
• Airfloat charcoal

Well, this is pretty cool. I've managed to get charcoal particle sizes, which are useful in my rocket fuel formula.

I have the airfloat charcoal specified in the formula. For the specified 80-mesh charcoal, I can use the charcoal I sized to be between 60-100 mesh. And, for anything that calls for 36-mesh charcoal, the 20-40 mesh charcoal ought to work just fine.

So, screens in various mesh sizes can be used to sort out different chemical particle sizes. They can also be used to sort rolled-star sizes if I have screens in larger mesh sizes.

Often, for sorting star sizes, 8-mesh, 4-mesh, 3-mesh, and 2 mesh (sometimes called 1/2-inch mesh screen) are used. The wire takes up just a little bit of the space per inch of screen, but in rough terms these screens could be used to separate rolled stars into these different sizes:

• Larger than 1/2-inch
• 5/16-inch to 1/2-inch
• 1/4-inch to 5/16-inch
• 1/8-inch to 1/4-inch
• Smaller than 1/8-inch

You get the idea. Different mesh-size screens come in very handy for sorting "things" into different size ranges.

How to frame your fireworks -making screens

Skylighter occasionally stocks pre-framed, round screens which are imported.

They also sell un-framed, square sections of stainless-steel screen, 11.75-inches square, in the 10, 20, 40, 60, and 100-mesh sizes.

Larger mesh sizes are available from various online sources. These stainless steel screens are not inexpensive, but being stainless steel, they can last a long time, especially if they are secured into a well-built wood frame.

Here's how I would frame a 20-mesh, 11.75-inch square screen.

I want to end up with a wood frame, which is 1/2-inch smaller than the unframed screen in both directions. Having the screen overlap the sides of the frame helps when it comes to stretching the screen tight.

I like to make the wood frame 3.5-inches deep so that plenty of chemical can drop through the screen and accumulate on the paper as I'm using the screen, without piling up and clogging the mesh.

For that reason, I use 1x4 lumber, which actually measures 3/4-inch by 3.5-inches.

I prefer poplar wood, which is readily available from stores like Home Depot. Poplar doesn't have much grain, so it doesn't warp much. Although it is classified as a hardwood, it is soft enough for my nails and staples to be easily driven into the wood. Certainly other woods like fir, pine, oak or maple could be used, but I'd be afraid that my staples wouldn't drive well into the harder woods like the oak or maple.

I showed how I cut paper tubes with a hand miter box and saw in Fireworks Tips #107. If you don't have a power saw, this same setup can be used to cut the lumber in this project.

Cutting 1x4 Poplar Wood for a Fireworks Screen Frame

I cut four pieces of the 1x4, 10.5-inches long. This will result in a frame with 11.25-inch outside dimensions, which is 1/2-inch smaller than my screen.

At the same time I cut four, 11.25-inch-long pieces of 3/4-inch wide, pine half-round trim, also from Home Depot. These wood strips will form the trim, which will cover the edges of the screen once it is installed on the 1x4 frame.

Four 1x4x10.5-Inch Pieces of Wood Cut for Screen Frame, and Four 11.25-Inch Pieces of 3/4-Inch Half-Round, Cut For Top Trim

I use some sandpaper to smooth the corners, edges, and ends of my wood. Then I apply two coats of fast-drying, spray polyurethane to all the surfaces of the wood before assembly. This finish will prevent the wood from soaking up water or chemicals over the years of use and cleaning that the screen will get.

Sand All Wood Surfaces, and Apply Two Coats of Spray Polyurethane

After the polyurethane coats are dry, the 1x4 frame is glued and nailed together. I like to use 6d (2-inch) galvanized finish nails, and polyurethane construction adhesive when assembling the frame.

6d, 2-Inch, Galvanized Nails, and Polyurethane Construction Glue, Used to Assemble Wood Screen Frame

I pre-drill the nail holes with a 1/16-inch drill bit to prevent the wood from splitting when the nails are driven in. Then I put a thin line of the glue onto the joint, after which I install 3 nails in the joint.

Pre-Drilling Holes, Gluing, and Nailing 1x4 Wood Screen Frame Together

Once the frame has been glued and nailed, I make sure it will sit flat on my workbench. I also check the two, diagonal, corner-to-corner measurements to make sure they are the same, which proves the frame is square. I make any adjustments necessary to ensure the frame is flat and square.

Time to install the screen: I use 1/4-inch long, galvanized staples, and a staple gun to attach the screen to the frame.

I first staple one of the sides onto the frame, with the screen in about 1/16-inch from the edge of the wood on two of the sides. I don't want any wire sticking out from the sides of the framed screen once it's done. Such wires could stick and cut my hands while I'm using the screen.

While I'm stapling this first side of the screen, I'm pulling it taut to make sure the side is stretched and straight as it is attached to the frame.

Stapling One Side Of the Screen To the Wood Frame

Then, as I make sure the screen is lying flat and that the second side is pulled square, tight and straight, I staple that second side to the frame. After each side is stapled, I hammer all the staples flush into the wood.

Stretching and Stapling Second Side Of the Screen

Now, I stretch the fourth, unsecured corner, out in the diagonal direction. This can be facilitated by inserting a sharp awl through the screen, and down into the wood. Then the awl can be "cranked" outward, stretching the screen in the process. This works best in the coarser-mesh screens. One has to be careful not to tear the screen when doing this with fine-mesh screens.

Stretching the Fourth Screen Corner With a Sharp Awl

I staple the fourth screen corner while stretching it out tightly, and then I staple the third and fourth sides. As I staple those sides, I pull the screen outwards, holding onto the extra 1/2 inch of screen, and pushing the wood inward with my finger as I do so.

This slight inward bow of the wood will hold the screen tight once it's stapled. Having that 1/2 inch of screen to pull on, is why I made the wood frame 1/2 inch smaller than the screen in both directions in the first place.

Securing the Fourth Screen Corner, and Stretching and Stapling Third and Fourth Sides

Now, I can slice off the extra screen, in 1/16 inch from the outside edge of the wood, with a sharp razor knife. The knife can be used to cut screens up through 20-mesh. For coarser screens and wire, the screen must be cut to the final size initially, and the awl method must be used to stretch the screen throughout the process.

Final Trimming of Excess Screen With a Sharp Razor Knife

Warning: Please be careful when trimming with the razor knife. I've worked with power tools my whole life, and I've never injured myself worse than I have with one of these knives. They can slip during the cutting and stitches will be necessary. Keep your "other" hand out of the way as you use the knife. All of this is supposed to be fun. Let's keep it that way.

And, in a final step, I use more of the glue and some 1-inch, zinc-plated wire brads to install the 3/4-inch, half-round, trim strips. I like using this trim because the inner sloping edge directs the chemicals toward the screen, and the rounded profile is soft on the hands during use.

Finishing Up the Screen By Gluing and Nailing On Trim Strips

As I'm using the glue I'm careful to apply enough so that the screen ends up embedded in the glue, which is stuck to both the top and bottom wood surfaces. This ensures that even with pressure from the hands during use over the years, the screen will stay in place, good and taught and straight, instead of developing a downward bow.

But, I don't apply so much glue that excess oozes out as the trim is applied. That would make a mess and clog some of the pores in the screen. Any excess glue that is present once the wood trim has been installed is carefully wiped off with fingertips. Paint thinner will remove glue from the screen if this is necessary.

I make sure there are no wires or screen-edges sticking out before the glue is dry. If there are, I can trim them now and seal those edges with a bit more glue.

Conclusion

Well, there you have it; one of the basic tools of the firework making trade, hand-made, and fit for years of service. It will be a pleasure to use the screen each time it is picked up, knowing that it was well made with quality materials.

When I'm done using the screen during a particular operation, I take the hose and thoroughly clean and dry it, storing it in a clean, dry location for future use.Enjoy and Stay Green,

Ned

How to Make a Hydraulic Rocket Press

By Ned Gorski
With technical assistance from Lloyd Sponenburgh

Introduction

In my experience, there are three basic machines, which become necessary as one gets deeply into fireworking: a ball mill, a star roller, and a hydraulic press. Ball mills were discussed extensively in Fireworks Tips #91, and I showed some options for star rollers in #92. Now it's time to look more deeply at rocket presses.

Commercial Rocket Presses

In past newsletters I have shown several of my hydraulic presses in action as I've made rockets, comets, pressed stars, black powder pucks, or fountains.

Some devices, like simple gerbs or black powder rocket motors, can be made by simply hand-ramming them with a rawhide mallet and a pounding post. Or they can be pressed with a hydraulic press.

Other devices such as whistle rockets or strobe rockets utilize more sensitive fuels, and require hydraulic pressing for their manufacture. Hand-ramming these motors is simply asking for a disaster.

Since I'm about to present projects showing how to make whistles, whistle rockets, and strobe rockets, I thought an introductory essay on hydraulic presses would be in order.

In the previous articles mentioned above I've shown my small Hobby Fireworks press. It's a nice press and was not too expensive. It sits on top of my workbench and is light and portable. I can take it to club events like the PGI convention. Unfortunately, Hobby Fireworks has gone out of business.

Hobby Fireworks Hydraulic Press for Making Rockets, etc.

Over the years I made some modifications to the press so that it suited my needs better. I replaced the 1/4-inch-thick steel plate on the top of the bottle jack with one that is 3/4-inch thick. The thinner one started bending a bit, and I want that plate to be perfectly flat.

I replaced the original 4-ton bottle-jack with a fast-action 6-ton one. The new jack can exert forces up to 12,000 pounds, which is about all I ever need, even when pressing large 4-inch comets and large rockets. Additionally, the new jack raises very quickly compared to standard-lift models.

The jack is available at Northern Tool, and currently it sells for $28, including a nice, collapsible lug wrench.

6-Ton, Bottle-Jack From Northern Tool

When I showed an advance copy of this article to my friend, Dan Creagan, he sent me a photo of a jack he had just found at WalMart, apparently identical to this one except it was painted black and had the Torin Brand name on it. It only cost Dan about $19.

I had the welding shop reinforce the press's adjustable cross "bridge" so that it would withstand the additional force exerted by the 6-ton jack.

I drilled holes in the back of each horizontal leg-support so that I could bolt the press down to the workbench to secure it during use.

The pressure release knob had a hole drilled through it and a 3/16-inch rod-handle installed for fast and easy operation.

This press has gotten a lot of use over the years, and if I had welding capabilities and I wanted a nice little press, I'd duplicate this model.

There are H-frame shop-presses available at various suppliers. In the past I've referred to one such press sold by Greg Smith Equipment. It's a floor standing unit, and weighs over 150 pounds, but it looks like a pretty nice press, has a good range of adjustability, comes with a pressure gauge, and sells for only slightly more than $200.

12-Ton H-Frame Shop Press From Greg Smith Equipment

Simple Do-It-Yourself, Hydraulic Press

Note: My friend, Jim B, has a favorite saying; "For every 10 pyros, you'll get a dozen different ideas on how to do any task in pyro." The ideas I present in the following project are designed to simply get your creative juices flowing. I seriously doubt anyone will build a model that is exactly like mine. But maybe these ideas can point you in the right direction.

In addition to the commercially-manufactured options described above, I got to thinking about a sturdy, relatively lightweight, bench-top press which did not require much welding. I'll describe one possibility that came to mind.

Simple Homemade Hydraulic Rocket Press

The setup and operation of the hydraulic bottle-jack is similar to the Hobby Fireworks press. I had six, 4x4-inch, 3/4-inch-thick, steel-plate shims cut at my local steel supply, to augment the adjustability of the press. Between the 5.5-inch travel of the bottle jack's piston, and the 4.5-inches of adjustability the shims provide, the press has a total of 10 inches of travel between all the way down and all the way up.

This allows me to adjust the press's top plate with the hex-nuts only one time per the particular device that I'm pressing. I never needed more than that 10 inches of adjustability for any of the devices I make. I've tripled-up the top hex-nuts because of the forces they endure during pressing. I don't want to be stripping any threads.

The Press's Main Frame:

The main frame of the press is made from four 3/4-inch x 36-inch threaded rods, nuts and washers from Home Depot. I had my local steel supply-house cut the bottom and top plates, which are 12-inch long pieces of 1-inch (thick) x 9-inch steel plate.

One-inch-thick steel plate is obviously very strong, and that strength is necessary to withstand the forces, which will be involved in pressing fireworks devices. I wouldn't want to use steel plates that are thinner than the ones I used, and I also wouldn't want to make them larger and spread the threaded rods out farther. This could lead to bending the plates.

The PVC plumbing pipe sections on the threaded rod uprights are there to keep me from cutting my knuckles on the threaded rod as I insert and remove devices in the press.

Installing a Blast-Shield

When I'm pressing whistle or strobe rocket motors, which use pressure sensitive, powerful fuels, the installation of a blast-shield is a good idea. The 1/2-inch thick plastic sheet will offer some protection just in case a motor "goes off" while it is being pressed.

The blast-shield is attached to the press and held in place with 3/8-inch eye-bolts, large fender washers, and hex nuts. Polycarbonate plastic such as Lexan is used in bullet-resistant windows, and serves well for blast-shields.

The other benefit of the PVC pipe on the threaded rods is to hold up the bottom blast-shield, eye-bolt supports.

Installing a Blast-Shield On a Hydraulic Rocket Press

Jack Return Springs

The two 7-inch springs, also from Home Depot, serve to return the bottle jack to its "down" position when the pressure-relief valve is opened. The top of each spring is attached to the 4x4-inch plate that is welded to the screw-out jack-post. The bottoms of the springs are attached to eye-bolts that are mounted in holes drilled through the bottom steel plate.

I had my welding-shop weld on small hex nuts for the top spring attachment at the same time they welded the plate to the jack post. This was the only welding required in this project.

Hydraulic Jack Return-Springs

Pressure Relief Valve Handle

To create an easily-operated handle for the jack's pressure-relief valve, a hole was drilled through the end of the relief valve. A piece of 3/16-inch galvanized steel rod, bent in an L-shape was inserted through the hole, and the small end was pounded flat on a vise-anvil to hold it in place.

Improvised Pressure Relief-Valve Handle

Holes in the Steel Plates

The holes in the top and bottom steel plates were drilled using a drill-press. That was the only large piece of equipment that was necessary in the fabrication of the rocket press. The threaded-rod holes were drilled at 9.5-inch centers, side to side, and 5.5-inch centers, front to back.

The jack is attached to the bottom plate with three, 5/16-inch bolts, which go up through the steel plate and into holes I drilled and tapped in the bottom of the jack. (Threading holes in metal is done with a tool called a "tap.")

Two extra holes were drilled toward the back of the bottom steel plate, through which bolts will go to attach the press to my workbench. This will make the press nice and steady as I'm pressing rockets.

Attachment Holes, Bolts and Nuts in Bottom Steel Plate

I used a hand-held grinder to smooth all the edges and corners of the steel plates. Then I primed and painted the plates using spray primer and finish paint.

Hydraulic Pressure Gauge

There are a few pressure-to-force (PtoF) hydraulic pressure gauges available to the pyro-hobbyist community. These gauges employ a one-square-inch-area piston, so they directly read out the number of pounds of force being applied to the item being pressed.

For example, if the PtoF gauge is reading 2000 psi, the actual force being applied to the tooling is 2000 pounds, the equivalent of 2000 pounds of concrete sitting on top of the tool.

An advantage to using one of these gauges is that you won't need to install a pressure gauge on the press's bottle jack.

A Pressure-to-Force Gauge Being Used With the Hydraulic Press

I personally like to use a gauge that is actually installed in the bottom of the bottle-jack. Doing so enables me to eliminate one loose, movable component, like the PtoF gauge, when I'm aligning and pressing devices in the press.

Using a gauge on the jack, though, requires that the gauge's reading be multiplied by the area of the jack's piston, in order to determine the actual force being exerted by the jack. I'll show what that means in a minute.

Installing a gauge on the bottle-jack presents what is probably the most challenging aspect of this project--drilling and tapping/threading the bottom of the bottle-jack, and installing a hydraulic pressure gauge. But, it's good to know how to do this, even if a PtoF gauge is going to be used.

Installing a gauge on a bottle jack requires the partial disassembly of the jack, drilling a couple of holes, tapping/threading the hole where the gauge will be installed, cleaning debris out of the jack, and reassembling it.

One of the nice things about the bottle-jack I'm specifying in this project is that it is relatively easy to take apart and put back together.

First, the rubber drain/fill plug on the back of the jack's cylindrical body is removed, and the oil that fills the jack is emptied into a clean pot. This oil can be filtered through a coffee filter and reused in the jack when it is reassembled.

When draining the oil, it helps to remove the pressure-relief valve. This valve has a 1/4" steel ball bearing down in the hole into which it is screwed. Carefully set the ball and valve aside, and finish draining the oil. Pumping the lever assembly a few times works the rest of the oil out. Now is a good time to drill the hole in the pressure-relief valve and install the L-handle.

Bottle-Jack, Oil Drained Out

The lever-arm has a couple of steel pins, held in with spring-clips, and is easily disassembled. (You are making mental notes of how all this goes back together, right?)

It's time to remove the large hex-nut at the top of the jack now. This requires that the base of the jack be held securely in a vise or a rocket press. (Waitaminnit, I'm making my rocket press! How can I hold the jack in my rocket press? I have 3 presses, and this will be my fourth.)

The hex-nut is then loosened with channel-lock-pliers or a large pipe-wrench. It may be necessary to whack the wrench with a rubber mallet or similar heavy object. The nut is screwed off when it is loose, and the central jack piston and outer jack shell-body can also be removed. The nut has a plastic O-ring gasket on it where it hits the main body, but this gasket is usually "glued" on with paint and does not need to be removed.

There is a "tapered" large rubber O-ring which sits in the groove that the shell-body came out of. Remove this O-ring. Remember that it was in there with the thin edge up, and the wide edge down.

Inside the jack, there will be a small, wire-mesh filter shoved in one of the holes in the base. Make a note of which hole it's in, and then remove it. Actually, this is a good recommendation, which has never worked for me in real life. Each time I've disassembled a jack, the filter has dropped out before I get to notice where it was in the first place. I'm not sure how they get the darn thing to stay in during shipping and/or operation.

I'll show in a moment how to determine which hole the filter ought to go back into when the jack is reassembled.

The screw-post will only unscrew so far as it extends out of the jack's piston. It is not necessary to remove this screw-post all the way. The whole jack can be taken to the welding shop when the 4x4 plate is welded to the screw-post. If one wants to remove the post all the way, some filing/grinding is necessary to remove the small "indents" which have been knocked into the top of the cylinder to hold the post in place.

Now is a good time to measure and make note of the diameter of the bottom of the piston. In this case it measures 1.375 inches. Squaring half that diameter (the radius) and multiplying that by Pi (3.1416) yields an area of the bottom of the piston of 1.5 square inches. (3.1416 x .6875 x .6875 = 1.5 square inches)

Because of that, when my new, jack-mounted pressure gauge is reading, say, 1000 pounds-per-square-inch (psi), I'll multiply that gauge's reading by 1.5 to determine the actual amount of force the jack is exerting on the tooling in the press, which in this example would be 1500 pounds.

Further Disassembled Bottle Jack

Once again holding the base of the jack in a vise or rocket press, I now carefully use a pipe wrench to loosen the jack's inner cylinder. I apply the wrench right down at the bottom of that cylinder in order to avoid crushing or distorting the tube as I loosen it.

Once the inner cylinder has been removed, another plastic O-ring gasket can be seen inside the base where the cylinder bottoms out. This O-ring does not need to be removed. Notice that there is a top and a bottom to the inner cylinder. The top is beveled on the inside lip to make insertion of the piston easy. The bottom has a flattened edge, which bears on the O-ring seal.

The small lever-operated jacking piston/cylinder should also be removed at this time. There is a metal washer and a 1/4" steel ball down in the base's recess which should also be removed.

Hydraulic Bottle-Jack, Further Disassembled

And, now, finally we've arrived at the final disassembly step. There is another 1/4-inch metal ball in the bottom recess of the base, held in with a plastic retainer. This can be seen in the base's large recess in the photo above. The retainer is removed by prying it with a screwdriver, and the ball is also removed.

I'm keeping all the little parts in a clean paper cup to prevent me from losing them as I go along.

There is also an over-pressure, safety relief valve, covered by a plastic cap. This assembly, including the cap, screw-out post, spring, metal-mushroom, and very small metal ball, is all removed and placed in the paper cup.

Final Bottle-Jack Disassembly

I can just hear ya hollering, "Crikey, Ned, what the heck have you gotten me into?"

It's really not as bad as it all sounds and looks. If you keep track of all the little parts, and remember how they all go back together, this can be fun. Really! There's learnin' happenin' here.

At this point, for my own education, I spent a bit of time envisioning how the jack works when it is being operated. The small jacking-piston and cylinder create high pressure using the principle of mechanical leverage. The pressurized oil is forced through the small hole in the bottom of that recess and up past the ball/hole/retainer in the large base recess.

All those balls in this device simply act as valves, sitting in nicely machined recesses, and only allowing oil to flow in one direction, pushing the ball slightly out of its recess. Oil pushing from the other direction forces the ball against the machined seal and shuts off the flow.

As it is needed, more oil is "sucked" into the small base recess from the main reservoir between the outer jack body and the inner cylinder.

The pressure in the cylinder jacks the piston up a small amount. The process is repeated as the piston gradually is lifted.

If too much pressure is generated inside the main cylinder, the oil can push the small ball and spring in the over-pressure relief valve and allow the excess oil to escape back into the main oil reservoir between the outer jack body and the inner cylinder. This acts as a safety to prevent the jack from being over-pressurized and dangerously rupturing.

And finally, when we want the jack to retract and go down, the pressure-relief valve is loosened. This allows oil to move past the ball at the bottom of that valve, and back into the main reservoir.

Since the only hole through which oil moves out of the main reservoir is the one leading to the bottom of the jacking-cylinder's small recess, that is the hole that the small filter will be replaced into (so it functions to remove debris from the oil as it circulates). I find which hole that is by blowing into it to make sure the air is coming out of the ball-blocked hole in the bottom of the small base recess.

And, keeping debris out of the whole jack is why I've completely disassembled it. After the next drilling and tapping steps are completed, all the parts will be completely cleaned before any reassembly. Small bits of metallic debris are the enemy of a properly functioning jack. They can become lodged in the various ball-valve assemblies and allow slow leakage, preventing optimal performance.

Drilling and Tapping the Jack-Base to Receive the Pressure Gauge

You'll notice, when looking at the jack base, that all the existing holes and inner "channels" that the oil flows through are located in the right side of the base.

Conveniently, this jack's base has a nice flat area on its left side, and plenty of room on the left-inside of the large recess where a hole can be drilled.

This is the point we've been heading toward. I want to drill a 3/16-inch hole down from the bottom-inside of that main base recess, but not all the way through the base. I drill this hole about 3/8-Inch deep.

3/16-Inch Hole Drilled Down Into Jack Base, Only 3/8-Inch Deep

I want to drill in from the left-outside of the base with the same 3/16-inch drill bit, until that hole hits the first hole that was drilled. I only want to drill as far as that first hole so that I don't hit any of the other inner channels in the base.

3/16-Inch Hole Drilled In From Side to Meet Up With Other Hole

The hole coming in from the side is drilled high enough from the bottom to allow the fittings I'm going to install later to clear the press's base plate. I also plan that hole so that it is centered in the bottom "thickness" of the base, so that the strength of the remaining metal surrounding my new fitting is maximized.

Drilling this hole, centered up 1/2 inch from the bottom of the base, accomplished all the above goals. And it kept the metal thickness between the hole and the bottom of the base no less than 5/16 inch, which is needed to withstand the internal jack pressures.

These two holes are gradually deepened until they hit each other, and no further.

Drilling 3/16-Inch Holes Which Join With Each Other

The two holes will form a new channel which will allow the pressurized oil inside the inner jack cylinder to reach the new gauge which will read out the same pressure that exists inside the cylinder.

Warning: The main power tool I'm using in this process is a drill-press. Like Norm Abrams says, "Read and understand the safety precautions concerning this tool before you use it." I do this drilling at low speeds. I firmly hold the piece I am drilling with a clamp and/or other tools. This drill-press can be my best friend, or it can slice my hands open and/or break bones. Be careful.

The hole in the side of the base is enlarged with a 5/16-inch drill bit (Q drill bit) enlarging a section about 3/4-inch deep. This side hole (only) then has threads cut in it with a 1/8-inch-pipe-thread tap.

Drilling and Tapping Holes in Bottle Jack Base

This is also a good time to drill and tap the bolt holes, in the flanges on the base, which will attach the jack to the press's bottom steel plate.

There, the hard part, the machining, is done. I now clean all the debris, excess paint, and metal shavings off of all the parts in a pot of clean kerosene or paint thinner. I pay special attention to the base to make sure all the small metal debris has been washed off of it and out of all its holes and channels.

After the parts have dried, the bottle jack is reassembled in the reverse order in which it was taken apart. Before adding the oil back into it, I attach the new pressure gauge using hydraulic fittings and Teflon tape. My local hydraulic-fitting supply-house was able to supply the fittings that I needed, and which would handle the pressure the jack will be exerting.

Pressure Gauge, Hydraulic Fittings, and Teflon Tape, Ready To Be Installed on Bottle Jack

These fittings were inexpensive, and it pays to use fittings certified for hydraulic pressure, rather than plumbing fittings which might rupture under that pressure.

The gauge sells for about $22 at McMaster-Carr. It is a 2.5-inch diameter dial, glycerin filled, 0-10,000 psi range, 1/4-inch pipe-thread bottom-connected, Model #4053K16.

But, the same supply-house where I bought the fittings, had a very similar gauge for only $16. I bought one for a spare while I was there.

I have temporarily hooked up gauges to lower-pressure jacks with iron pipe fittings. But those plumbing fittings are not rated for the 8000 psi that will be developed in this new jack when it is putting out the full 6 tons of force.

Remember that when the gauge reads 8000 psi, that reading is multiplied by 1.5 to determine the force that the jack is exerting. That means an 8000 psi reading equals 12,000 pounds of force, the maximum force this jack is rated for. That's why I chose a gauge with a range of 0-10,000 psi.

The Teflon tape is carefully wrapped on the pipe threads, in the direction that will tighten the tape wraps as the male threads are screwed into the female fittings. 4-5 wraps of the tape are put on each threaded section. I'm careful not to overlap the tape down onto the end of the fittings, where bits could break off and clog the channels or valves in the jack.

After the gauge was installed and all the fittings tightened up, I filtered the oil through a coffee filter and filled the jack back up with the oil through the fill hole on the back of the jack's body. I pumped the jack up and down a few times to work any trapped air out of the system. Then the jack was installed on the rocket press.

Hydraulic Bottle Jack With Gauge, Installed On Rocket Press

I topped the oil off with more, new hydraulic-jack oil until it started to run out of the fill-hole in the main jack body. Then I installed the rubber plug.

I put my Pressure-to-Force gauge on the jack-plate, and jacked the press up to various pressures. This was to make sure that, indeed, the PtoF gauge read 1.5 times what the gauge on the bottle jack was reading. I also removed the PtoF gauge, and jacked the press up to its maximum pressure and let it sit there for a while to make sure it wasn't losing any pressure through leaks or badly sealed steel-ball valves.

Final Test of the New Rocket Press, Bottle Jack, and Pressure Gauge

Everything worked great, so I moved the press into its permanent location on my work bench and attached it there with bolts which go through the two extra holes in the back of the bottom steel plate, and on through the workbench top.

Conclusion

Great! My fourth press is now up and running. Why the heck do I need four presses? I think I'll paint and clean up my old Hobby Fireworks press and see if I can find a new pyro who wants to give it a good home.

There's one final thing I thought about this press when it was done: "Hey, I built that thing. I know every part of it, and if anything goes wrong with it, I know how to fix it."

I bought an extra bottle jack while I was working on the project, and drilled and tapped it at the same time as the main one. That way I have replacement parts, or the whole complete replacement jack if necessary.

This all results in a good feeling, and I suppose that's why I do all of this in the first place.

Stay Green, and now on to more, ahh, Pressing matters.

Ned

How to Make Flashing Fireworks Strobe Pots

Introduction

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.

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	Percentage	16 Ounces	450 grams
Ammonium perchlorate	0.57	9.15 ounces	257.1 grams
Magnalium*	0.24	3.8 ounces	107.1 grams
Barium sulfate	0.14	2.3 ounces	64.3 grams
Potassium dichromate	0.05	0.75 ounces	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:

Meinhart Pink Strobe Composition

Chemical	Percentage	16 ounces	450 grams
Ammonium perchlorate	0.57	9.15 ounces	257.2 grams
Magnalium, 200 mesh	0.15	2.45 ounces	68.6 grams
Strontium sulfate	0.11	1.85 ounces	51.4 grams
Strontium carbonate	0.08	1.2 ounces	34.3 grams
Parlon	0.04	0.6 ounces	17.1 grams
Potassium dichromate	0.05	0.75 ounces	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.

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 spiral-wound 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.

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	Percentage	16-Ounces	450 Grams
Potassium perchlorate	0.74	11.85 ounces	333 grams
Red gum	0.12	1.9 ounces	54 grams
Charcoal, airfloat	0.06	0.95 ounce	27 grams
Potassium dichromate	0.05	0.8 ounce	22.5 grams
Aluminum*, flake 100-325	0.03	0.5 ounce	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 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 on-center 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.

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 How to Make Electric Matches and Wiring Fireworks and Firing Systems in a Fireworks Display.

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

Click here to see a video of the white and red strobes.

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:

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.

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

How to Make a Model Ammonium Dichromate Volcano

Introduction

A while back I received an email from Harry:

"Have you ever made an ammonium dichromate volcano? They are really popular with parents and teachers and look great daytime or night."

I responded: "Never learned how to make a volcano. Led a deprived childhood. No way they’re doin’ anything like that in science classes nowadays."

Making a volcano would, of course, be exactly the sort of school project which would capture the imagination of so many young students.

Harry shot back: "Neat little effect. The ammonium dichromate burns by itself, but you can add other fuels to make more lifelike 'lava.' For instance, charcoal 10 or 20-mesh. I imagine there's some flake titanium, ferro-titanium, etc. that would work as well. You could provide volcano formulas for high school projects."

Well, I was intrigued. I've made 16-inch ball shells and 36-inch girandolas, but never an ammonium-dichromate volcano. I couldn't let that stand for long. So I asked Harry to send me a few tubs of the ammonium dichromate, and I put it on my to-do list.

In the meantime, I did a little research on the Internet, and also found a couple of paragraphs about the volcano in the Skylighter Project Plans pages.

Warning: So, first off, a bit of a warning: Ammonium dichromate is rated as a hazardous toxic chemical on its MSDS. One should not inhale its dust, but that's not too tough to avoid since it comes as relatively large orange crystals, not a dust that gets easily airborne.

One should not ingest it. Well, Duh!

One should avoid skin contact. Wear rubber gloves if you're gonna touch the stuff (which is not necessary to create one of these volcanoes). Avoid eye contact. The stuff can cause cancer.

So, exercise appropriate caution with this chemical. If you're going to be making a volcano like this for a science fair, perform all actions and experiments with it outdoors, and when the volcano is "erupting" don't allow anyone to breathe the small amount of smoke and ash, which rises off of it.

Use common sense. I know, I know. Common sense is not in common use nowadays to protect folks from harm. Since everything even remotely dangerous is becoming illegal, folks are increasingly being born with no common sense chip. But, use common sense anyway. There, you see? You got me started.

The scientific stuff: science for kids - old and young

I’m not much of a chemist, but I did find this information interesting, and some other folks might as well.

Ammonium dichromate is sometimes referred to as Vesuvian Fire due to its use in the creation of these small volcano replicas.

Ammonium dichromate's formula is (NH₄)₂Cr₂O₇.

Ammonium Dichromate, Skylighter #CH5500

When it burns, it decomposes according to the following equation:

(NH₄)₂Cr₂O₇ (solid) -> Cr₂O₃ (solid) + N₂ (gas) + 4H₂O (gas)

The gaseous byproducts are simple nitrogen gas and steam, so they are innocuous.

Chromium Oxide Ash Left After Ammonium Dichromate Volcano Burns

The solid product is chromium (III) oxide. What remains after the volcano burns is this solid, grayish-green ash. The chromium in it is toxic and possibly carcinogenic, so care should be exercised when handling it and disposing of it. Some of this ash flies up into the air when the volcano is burning, so you don’t want anyone close enough to it to breathe the stuff.

The chromium oxide can reportedly be used in a thermite reaction to produce elemental chromium metal, so I'm going to save the chromium oxide ash to try to use it in such a reaction, since I am planning an article on thermite reactions.

A volcano project

I decided to go simple, and make a "volcano" out of a can and heavy-duty aluminum foil. I formed a lip at the bottom of the aluminum foil "cone" to catch the ash as it formed.

Making an Aluminum Foil/Pop-Can Volcano

I lit the top of the ammonium dichromate with a propane torch, and it burned and created a "volcano" effect, but at times the flame went deep into the orange crystals, down the sides of the can, and propelled some of the crystals up and out of the can, unburnt. I was not completely pleased with the effect that was produced.

So I decided to try a shallow, tuna-fish can, sitting on top of the pop can.

Aluminum Foil Volcano Made With a Shallow Tuna Can

This volcano burned a little better than the first one, but still the flame worked its way down the sides of the can, and the ammonium dichromate did not burn evenly. I still was not satisfied.

I also noticed that igniting the ammonium dichromate with the propane torch was not all that easy. The pressure of the propane blew the crystals out of the way of the flame, and although some of them eventually lit and initiated the desired continuing reaction, the pile did not ignite right at the top of the heap.

So, I decided to try something really simple. I made a "tray" out of flat aluminum foil with the edges turned up to catch the ash. I poured a cone of about a half-pound of the ammonium dichromate in the middle of the foil tray, and inserted a 6-inch length of Visco-fuse into the middle of the pile of orange crystals.

Simple Pile of Ammonium Dichromate to Create a Model Volcano

Once the Visco fuse burnt down into the cone of crystals, they ignited and a nice volcano-action formed and burned until only ash remained.

Well, then I thought that the way to get this baby really looking like a volcano, but still burn like it did in this last test, was to form the aluminum foil over the cans, but not cut the opening. I just piled the ammonium dichromate on top of this "mountain" on the flat section and inserted another piece of Visco.

Daytime Ammonium Dichromate Volcano

I was really pleased with how this volcano looked and performed.

Click to see a Video of the Volcano

I think it almost looks like the real thing with glowing, flaming lava flowing down the side of the Mt. St. Gorski.

Making model volcanoes this way uses about 1/4 pound of the crystals per volcano.

Nighttime volcanoes

I thought I'd make a few other versions of the ammonium dichromate volcano at night.

For the first one, I repeated the procedure I followed in the last daytime test. This looked pretty cool as the "lava" burned and flowed down the sides of the "mountain."

Honestly, I like watching the volcano better in the daytime when I can see the greenish ash being formed and flowing down the sides of the hill.

Click to Play Nighttime Ammonium Dichromate Volcano Video

For the second nighttime volcano, I did the same as above except I stirred in a tablespoon of 36-mesh charcoal to see what sort of effect that would produce.

As this volcano burned, a lot of orange, charcoal sparks rose up into the air above it, creating an effect that was different than the standard, ammonium dichromate-only volcano.

Ammonium Dichromate & Charcoal Volcano

For the third nighttime test, I mixed in about a tablespoonful of medium flake aluminum, and for the fourth and final test I added about a teaspoon of fine spherical titanium.

The addition of these metal fuels seemed to slow down the burning reaction, and did not produce the silver-white sparks, that I was half-expecting. There was an interesting, different sort-of molten flowing effect, as the reaction seemed to almost melt the ammonium dichromate and metal together, causing molten "lava" to flow down the mountain.

As a last offering to the pyro-gods, I simply poured about a half-pound of the ammonium dichromate onto a bare patch of ground and lit it with the propane torch.

Simple Ammonium Dichromate Volcano On the Ground

This caused the little volcano crystals to ignite from the sides and burn toward the center, and this was probably my favorite effect of the night. (After it, I had to get a shovel and completely clean up the green ash from the area.)

Click to see Video of Volcano Project

Conclusion

This was a fun little science project. I saved some of the ammonium dichromate for when my grandkids visit, and I'll introduce them to something they’ll probably never have the chance to see in science class. And there’s enough left to show them how to make a school project volcano just in case that time comes.

I learned something today working on this model volcano, and that's never a bad thing.

Take care and have fun,

Ned

How to Make Chinese Sky Lanterns

By Ned Gorski

Can mere mortals make sky lanterns?

Click to watch the sky lantern video.

I gotta admit, I've seen sky lanterns around for several years. I've seen 'em advertised right here by Skylighter. Have seen them at displays and club events. But, honestly I never gave them much thought, and I wasn't much tempted to buy any.

But, then I saw the latest Skylighter ad for them, and I thought, "I wonder how sky lanterns are made." Ya see, one of the things I enjoy most is learning how something is made. I watch This Old House and The New Yankee Workshop, just to see how they do stuff, even though I've been doing that kind of work myself for a living for 30 years.

So, I had Harry send some of the flying lanterns to me. By the time they arrived on my doorstep, I was excited to see them. I opened the package up, looked at the treetops to make sure there wasn't too much wind blowing, and I hustled my wife and granddaughter outside to fire the first one up.

I enjoyed finding out how to light the paper lantern, and how to let it inflate and launch it. And, the three of us really did have fun watching it lift off, and then gazing at it for minutes until it flew out of sight and we couldn't see it any more. Then I quickly got another one out and launched it as well.

My son and his family came over last Sunday, and I knew I just had to demonstrate these new toys for my grandsons. The photos below say it all.

The Next Generation of Gorskis with Paper Hot Air Balloons

So, now, back to my original quest: How to make sky lanterns.

Note: I'm gonna tell you how I ended up successfully making these homemade paper hot-air balloons. But, as with any pyro project, I learned some lessons the hard way, and I had some significant failures. I'll note these as I go along in this hot paper tale.

Sky Lantern Autopsy

A little reverse engineering revealed:
Weight of a flying lantern	2.7 ounces
Thin bamboo hoop at bottom	45.75" circumference, 14.56" diameter
Weight of hoop	0.3 ounces (with a little paper and glue still hanging onto it)

Bamboo is about 1/16" x 1/8"

X of thin wire tied to hoop

X of wire is "woven" through waxed cloth and paper "burner"

Original Sky Lantern Burner, Which Weighs 0.9 Ounce, Including Wire

The burner is composed of a 2.5" x 17" piece of wax-impregnated cloth, folded in Z-fashion back on itself 5 times.

In between each Z-fold of the waxed cloth are five 2.25" x 3" pieces of thin, coarse-fiber paper, about the weight of 40# kraft paper.

(The cloth/paper burner smells "nice," sort of like the scent of roses. Maybe the young Chinese lady who made this one was wearing some fragrant perfume.)

Note: I have also seen sky lantern burners, which resemble fiber-reinforced blocks of wax. I don't know how they are made and have not tried to duplicate them.

The "bag" of the balloon is made up of white tissue paper. This paper has been treated with a fire retardant; it does not catch fire when touched by a flame. It just scorches a bit.

The tissue paper bag weighs 1.5 ounces.

There are four panels (called gores in the ballooning world) that make up the balloon, and they are glued together and to the bamboo hoop.

Here's a sketch of one of the gores, with a bit added to the edges to allow for gluing.

Sketch of a Sky Lantern Paper Panel
(One square = 1")

I flew one of these fire-lanterns in my high-tech, windless wind-tunnel (actually my garage, emptied of any gas cans or other combustibles). I tethered the Chinese lantern to a weight with some very thin, light string as it burned. The fuel pack burned for 4.5 minutes.

I added 0.05-ounce pieces of wire, one at a time, to the bottom wire "X" of the balloon as it "flew," and found it would carry 0.25 ounce of payload before starting to sag toward the ground garage floor. That 0.25 ounce, added to the paper-lantern's original weight of 2.7 ounces, added up to a maximum flying weight of 2.95 ounces for a lantern with this internal volume.

It is the internal volume of a paper hot-air balloon, and the heated air it can contain as well as how much that air is heated, which determines its maximum carrying capacity.

Skylighter Sky Lantern Carrying 0.25-Ounce Payload

Note: The information above is important. These flying lanterns are delicately balanced for flight, and they are just light enough to allow them to fly. If they were much heavier, they would not leave the ground. Due to some circumstances, which I describe below, my first balloon ended up weighing 3.9 ounces, and obviously would not have flown.

So, let's make a paper sky lantern

I went up to my local Hallmark store and bought some nice tissue paper in different colors.

Some checking online produced some leads on products designed to flameproof paper. One company, Universal Fire-Shield (www.firechemicals.com), sells a product, Universal Paper Shield P-3000, designed to fireproof paper products. I ordered some. They sell a quart spray bottle for about $30, including shipping. This would be enough to treat about a dozen paper hot-air balloons.

Tissue Paper, and Fireproofing Product

I hung 4 pieces of the red tissue paper on a clothesline, and sprayed them with the Paper Shield until they were saturated. After they were dry, I tried to burn a little piece of the paper, and it only scorched like the original fire-lantern paper, but it would not burn.

Fireproofing the "Laundry"

Note: On my third attempt to make one of these paper lanterns, I decided to try to spray the untreated bottom half of the balloon after it was assembled, in order to skip the step described above. I hung it up, slightly inflated it with my heat-gun, and started spraying it. The tissue paper soon started to weaken, sag, and tear, ruining the balloon. Crud! Another lesson learned.

I decided that the process of hanging the panels like laundry works best. The upper corners of the sheets will be cut off when the gores are cut out, so I don't spray those areas because they get weak when they are wet, and allow the clothespins to tear through the paper and sometimes that has the paper to tear loose from the string.

Warning: Paper Shield has an acid in it, and it will damage a concrete garage floor slightly. It's best to have a plastic drop cloth under the clothesline to protect the floor. Don't breathe its fumes or get it on your skin.

The red tissue will be the bottom of the paper hot-air balloon, which will be the only part that gets exposed to the flame. The top of the balloon will be blue paper, and it does not need to be treated.

I glued a piece of the red paper to a piece of the blue with thin stripes of Elmer's, and I did that four times for the four panels, and let the panels dry.

Note: The Elmer's glue tends to wet the tissue paper, bleeds through, and tries to stick to the other stuff around it. In an attempt to avoid this problem, I used hot glue when building my first balloon. This worked nicely during construction, but when I fired that baby up, the hot-glued seams at the top of the balloon let go completely. I did not think the internal temperature would get high enough to cause this problem. I was wrong. (My wife, Molly, told me later on that she wondered about me using the hot glue, and that she thought it would melt when the burner was lit. Oh, well.) The hot glue, which is significantly heavier than the dried Elmer's, also contributed to the excess weight of the first model.

After gluing the red and blue sheets together and letting them dry, I cut the four panels out with scissors, using a kraft paper template that I made based on the sketch above. Folding the kraft paper in half lengthwise, and then every 6" made the pattern transfer easy.

Tissue Papers Glued Up and Cut to Form Balloon Panels

Then it was time to glue the lantern gores together to form the Thai-lantern's "bag." I laid one of the gores, unfolded and open, on the worktable with the inside up. (The outside of the gore is simply the side that I think looks best.) Then I laid a gore, outside up, on top of the first gore, weighed the two down, and glued the right sides together with a thin stripe of Elmer's. The table had waxed paper on it so that any glue that seeps through wouldn't stick to it.

I then folded the top gore's loose side over on itself, so that half's inside was facing up, inserted some waxed paper between the glued side and this loose side, and laid the third gore on top of that one. I glued those two loose edges together, inserted more waxed paper, folded the loose half of the third gore over, laid the fourth and final panel on top, and glued those loose edges.

Then the last step was to fold the loose half of the top, fourth gore, over on itself, and fold the loose half of the bottom, first gore over onto it, and glue the loose halves together. (This all sounds much more complicated than it actually is. Once you try it, it'll all make sense.)

Then I pulled the glued edges up and off all the waxed papers, propped the panels apart from each other and from the table, and allowed the seams to dry.

Gluing Sky Lantern Gores Together to Form Balloon's Air Bag

Another Failure Note: On my first attempt to build one of these, I tried gluing the bag together with the panels inside out. I let the seams dry, and then I tried to turn the bag right side out, so that the seams would be hidden. This probably would have worked OK, but the fireproofed red tissue paper was somewhat brittle because of the fire-treatment, and as I tried to turn it inside out, it started to tear and crack at the bends and creases. I had to try to repair these tears with clear packing tape, which increased the lantern's weight, and made it ugly, and not something to be proud of. I decided to simply allow the seams to be on the outside of the bag in future models, and avoid the "turning inside-out" step.

Making the sky lantern's bamboo hoop

Home Depot had some 1" diameter bamboo poles in their lawn and garden department. I bought one and carefully split it into thin strips. I took one of the strips and smoothed it with sandpaper and a razor knife until it was about the dimension of the original lantern's bamboo. I only sanded the "interior" side of the bamboo because I did not want to weaken the smooth, exterior side of it. Then I glued it into a hoop with the same circumference of the original.

Tiki-Torch for Bamboo Strips & Sky Lantern Bamboo Hoop

Another source of good bamboo strips is from a "Tiki-Torch" pole. These are often split to obtain bamboo strips for girandola frames, wheel frames, and the like. (Or you can steal some green bamboo from Harry Gilliam's bamboo-infested front yard.)

Making the Sky Lantern Burner

I had some blue, industrial paper-towels, and I decided to melt some grocery-store canning-wax, and impregnate the towels with the wax in an attempt to duplicate the waxed fabric that I found in the original fire-lantern's burner.

Warning: Canning (paraffin) wax is very flammable, and should only be melted over low heat in a double boiler. It should never be exposed to open flames or high heat.

Coating a Paper Towel With Wax to Make Sky-Lantern Burner

I took a strip of this waxed paper towel, and burned it alongside a strip of the waxed material from the original lantern's burner. Both samples burned identically and for the same amount of time.

I had some coarse, recycled kraft paper, and cut it into rectangles to match the original burner's paper layers. Then I cut some strips of the waxed paper towel to match the original burner, and sandwiched 5 pieces of the kraft paper in between each layer of the waxed paper-towel.

Then I stacked the layers of the burner together, punched 4 holes through all the layers with an awl, and threaded two pieces of wire through the holes.

The ends of the wire were then wrapped around the bamboo hoop and twisted tightly to secure the ends. The hoop was then carefully glued into the end of the lantern's tissue paper bag, and the glue was allowed to dry.

Assembling Paper-Lantern's Burner & Attaching It to Bamboo Hoop

A simple alternative burner can be made by simply installing a plain X of wire on the bamboo hoop. Then strips of cotton-ball like material can be saturated with rubbing alcohol, draped over the center of the wire X, and ignited when launching the balloon. But keep in mind, you have to use this method right away; the alcohol fuel evaporates, and these have no "shelf life."

Materials Needed For a Rubbing-Alcohol, Cotton-Swab Balloon-Burner

All that remained, then, was the installation of the "FAA" aircraft identification numbers, and a flight in the "test chamber."

Test Flying Homemade Sky Lantern

This paper hot-air balloon's final weight was 3.0 ounces. At about 50-degrees F in my garage, it was able to carry a payload of .55 ounces of the wire pieces before it started to sag toward the ground.

After this testing, some soot and moisture condensed on the inside of the lantern. I was able to allow it to dry out, attach a new burner, and fly it outdoors for real. It was about 40-degrees F outside on the evening that we flew it, and it really took off for the heavens very quickly.

My Lovely Assistant Molly Launching a Homemade Sky Lantern

Note: The flying lantern in on the right, Molly is on the left. The fact that Molly's attire matched the balloon she was launching was entirely coincidental. That's my story and I'm sticking to it.

Click to Watch a Video of the Launch.

Conclusions

This was a fun and educational project. I learned a lot about what to do and what not to do, when making one of these little hot-air balloons. This project was not as easy as it might look.

Based on my experience with flying the paper lanterns tethered in my garage, I think it would be fun to fly one outdoors in windless conditions, tethered by a short wire leader and a roll of light thread. It could be flown like a kite, reeled back in when the burner burns out, reloaded and flown again.

This project resulted in me having a high amount of respect for the folks overseas who turn these things out by the thousands, which fly successfully every time. I'm continually amazed by the low cost of a device like this, sold by Skylighter, compared with the time and materials I invested in producing a successful one.

It was fun to make these lanterns, and I enjoy knowing how to do it. If I had to come up with a bunch of 'em for an event like a wedding, holiday, or memorial service, I sure wouldn't be making them, though.

Happy Flying, and Stay Green,

Ned

Making a Firework Star Pattern Shell

By Ned Gorski

Introduction

A firework shell which bursts with a ring pattern, a smiley-face, or a star pattern can be a unique and creative addition to a fireworks display. Suddenly, after a procession of fairly typical full, spherical shell bursts, a simple ring of stars, or a display of four or five of them fired simultaneously, changes the focus of attention of the audience. "Hey, here's something different," they'll think to themselves.

Firework Pattern Shell with a Star Inside a Ring

Pattern shells have some distinct advantages and disadvantages to their construction. They don't use nearly the quantity of firework stars that a fully loaded shell would use, so if I have a few stars of a particular size and color, they might come in useful in a pattern shell. Patterns can be chosen to coincide with a particular theme in a show, with blue stars in a patriotic section, or pink hearts in a romantic interlude.

On the other hand, it will be hit-or-miss when it comes to the pattern's orientation in the sky when the shell bursts. The smiley-face may display upside-down, or the ring may be seen on edge by a portion of the audience, looking more like a simple line in the sky. For this reason, most display designers choose to fire 4, 5, or 6 of the same or similar patterns at the same time. That will usually result in the audience in a particular location seeing at least 1 or 2 of them in the desired orientation.

Six Ring Pattern Shells, With Only Three Oriented Toward the Camera

If 6 ring-pattern shells of different colors are fired at once, the audience at one end of the field may see, say, the blue and red ones as true rings, and imagine all of them being the same shape.

Ring shells can use simple color stars, which leave no tail behind them, as in the photo above, or tailed stars can be employed, as below.

M.C. Escher's Lithograph, "Vuurwerk" (Fireworks)

This Escher print, "Vuurwerk," is on the cover of Pyrotechnica XI. It shows a pattern I would expect a ring shell of slow-burning, silver-tailed stars to display. It would have to be oriented so that the ring broke "flat" in order to display the "parasol" of stars just right.

A small rising comet tail produces the "handle" to the umbrella.

An advantage to using patterns such as rings, stars, squares or triangles is that they can break in many directions that still have them look correct, as long as they don't break on-edge to the viewer. A smiley-face has to break in just the right direction to be recognizable.

The star-in-a-ring pattern shown below would look correct if it was rotated any number of degrees clockwise or counter-clockwise. It would also look fine if it was flipped 180 degrees front to back. The only way it would not show up well is if it broke on-edge to the viewer.

Star in a Ring Pattern Shell

My friend, Mike B., made the heart-pattern shell shown below. While it did not break on-edge to the audience, unfortunately it did break almost upside-down. The fortunate thing about hearts is that they look good in almost any orientation, and the audience can make out what they are supposed to be representing.

Heart Pattern Shell

Making a pattern shell

I want to make a blue star-pattern shell. I don't want to make my stars much smaller than 3/8-inch in diameter, so that they burn long enough to allow the pattern to show up. Additionally, ball shells break more symmetrically than cylinder shells. For these reasons, I've settled on assembling an 8-inch ball shell for this project. With 3/8-inch stars, a smaller shell simply wouldn't allow the use of enough stars to create a nice star pattern.

The general construction techniques I'll be using when assembling and finishing this shell were detailed in Fireworks Shells in 2-1/2 Days - Part 2, Part 3 and Part 4. I'll be using 1/4-inch time-fuse in this shell, though, instead of a spolette. The use of time-fuse was explained in Really Nice 4" Platic Ball Firework Shells.

The first thing I did was draw a pattern of the stars that would fit the inside diameter of one of my 8-inch shell casings, which has an ID of 7.25 inches. 360 degrees divided by 5 gave me 72 degrees between each of the points of the 5-pointed star, which I measured out with my protractor.

My 3/8-inch pumped stars actually end up being about 7/16-inch in diameter once they are primed, so I drew lines of that size star on my pattern. Precision in these initial planning stages, right through the actual construction of the shell, will result in a more precise star-pattern in the sky when the shell bursts.

Star Pattern for an 8-Inch Ball Shell

I took a piece of tissue paper, cut a circle out of it about 1/2-inch larger in radius than my drawing above, and traced the star pattern onto it.

Star Pattern Traced Onto Tissue Paper

Then I made some blue stars. Firework Shells in 2-1/2 Days - Part 2 and Part 3 included instructions for making and priming pumped stars.

Although I didn't need a large number of these stars, it was important that all the stars were consistent in size. For this reason I used a 3/8-inch star plate to make a pound of the Shimizu Blue star composition included in the table of formulas in 14 Great Cut Star Formulas.

Shimizu Blue Star Formula	Percentage	16-ounce batch	450-gram batch
Potassium Perchlorate	0.61	9.75 ounces	274.5 grams
Copper Carbonate	0.12	1.9 ounces	54 grams
Parlon	0.13	2.1 ounces	58.5 grams
Red Gum	0.09	1.45 ounces	40.5 grams
Dextrin	0.05	0.8 ounces	22.5 grams

I dampened this star composition with an additional 10% water, and pumped and dried the stars. I primed them with the black powder "meal prime" which is also in that star formula table cited above. I add an additional 5% of 200-mesh magnalium to the prime, which improves the ignition of perchlorate stars.

Constructing the Shell

As I said above, the shell was constructed in the standard fashion, except for the details below.

Once I had the time-fuse and passfire-tube installed in the shell casing, I hot-glued a 1.5-inch wide tissue paper ring inside each hemisphere at the equator. These bands served the purpose of locking the shell's contents into the hemispheres later on when I closed the shell.

Tissue Paper Bands Hot-Glued at the Equators of Each Hemisphere

Then I filled the fused hemisphere with black-powder-coated rice hulls, folded the tissue-paper band over onto the hulls, and hot-glued a tissue-paper disc onto the whole shebang to cover and seal it. As I loaded the hemi with the coated hulls, I packed them tightly one layer at a time to make sure the casing was solidly filled. I also filled the hemi slightly higher than the equator. This half of the shell held 29.4 ounces (825 grams) of the coated hulls.

Fused Shell Hemisphere Filled With Black-Powder-Coated Rice Hulls

Then I filled the un-fused hemi with coated rice hulls up to within about 3/8 inch of the rim. I made sure the rice hulls were tightly packed and very level. This filling was loosely capped off with the tissue paper disc which had the star-pattern traced on it.

Second Shell Hemisphere Filled to Within 3/8 Inch of Rim, and Capped With Star Patterned Tissue Paper Disc

Starting with the points of the star, blue stars were lightly hot-glued onto the tissue pattern. These stars only had a small dot of hot glue put on them where they touched the pattern. Just before the shell bursts, the tissue paper disintegrates and the stars are free to fly out in the star shape.

Hot-Gluing Blue Stars Onto Tissue Paper Pattern

Then I filled in around the stars with more black-powder-coated hulls, tightly filling all the voids and bringing the level of the rice hulls slightly above the rim of the casing. This hemi actually took about 35 ounces (1000 grams) of the coated rice hulls, for a total of about 4 pounds (1800 grams) in the whole shell. This was all capped with another hot-glued disc of tissue paper.

Black-Powder-Coated Rice Hulls Filled in around Blue Stars, Both Hemispheres Capped and Ready to be Mated

Because the tissue paper rings and discs were glued to the shell casing hemispheres, it was easy to flip one of the hemis over onto the other and close the shell up, ready for pasting, lifting and leadering.

With the blue stars sandwiched between the layers of tissue paper, with the rice hulls really packed in tightly and the hemis overfilled and slowly tapped and brought together, the star pattern was held firmly in place.

I've developed a nifty trick for bringing the stuffed hemis together at the equator. I use 4 strap-clamps, available at Home Depot or stores which cater to woodworkers.

As the clamps are slowly tightened, tapping the shell with a solid, heavy rod brought the two halves together and solidly packed the contents. Then the joint was closed with strips of masking tape. This method is so much easier than "laying" on the shell while tapping it in order to close it.

Closing an Aerial Shell Using Strap-Clamps and Masking Tape

Warning: I use a non-sparking, aluminum rod for tapping on the shell. But, the metal strap-clamp parts are not non-sparking. I'm working around relatively exposed black powder on rice hulls during this process. I'm very careful to avoid smacking the metal clamp ratchets, which could potentially cause sparks.

Then I pasted the shell, allowed it to dry, and lifted and leadered it. A small rising comet tail was attached to direct the viewer's eye toward where the shell will break.

Completed 8-Inch Star Pattern Aerial Fireworks Shell

When I shot this shell, it did indeed break a bit on its "side" relative to the camera, as shown in the photo below. There were viewers down and to the left of the shell-burst, and they said that the star really looked nice, big, and symmetrical.

Star Pattern Shell Bursting

Oh, well, maybe I'll get to see it next time.

Here's a link to a video of the shell in action.

Final Thoughts

I enjoy making pattern shells. They offer a unique challenge in shell construction, and use less of the chemicals that go into stars. More black-powder-coated rice hulls are used than in a typical chrysanthemum or peony aerial shell, but these are the less expensive ingredients.

I think an audience enjoys the variety that these pattern shells bring to a display.

The next time I make a shell like the one in this project, I think I'll add a red ring around the blue star pattern so the sky is filled a bit more when the shell bursts.

I'm working on my version of a way to at least have aerial shells burst with their equators level with the earth. This will allow rings, star patterns, etc, to display well for anyone underneath them. The method is one that I've heard about over the years, but have never seen, where a rope is attached to the bottom of the shell to produce drag on the shell's way up. This keeps the shell oriented with its "bottom" down on the way up.

I plan on shortening the shell's time fuse delay so that the shell bursts before apogee while it is still oriented correctly. I'll keep you posted on the progress in this project.

Have fun and stay green,

Ned