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.

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

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.

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.

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.”

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.

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.

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.

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.

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.

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.

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.

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.

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.

Results

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

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

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 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.

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.

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.

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.

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.

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 1×4 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.

I cut four pieces of the 1×4, 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 1×4 frame.

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.

After the polyurethane coats are dry, the 1×4 frame is glued and nailed together. I like to use 6d (2-inch) galvanized finish nails, and polyurethane construction adhesive when assembling the 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.

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.

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.

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.

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.

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.

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.

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