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Tiger Willow Shells in 2-1/2 Days, Day 1




This is the first part of a series of 3 articles by PGI Grandmaster Ned Gorski, detailing the production of 8" ball shells in a minimum timeframe, possibly at a 3-day fireworks club event. The original series ran in 2007 in the Pyrotechnic Guild International's Bulletins #152-155. This is a somewhat revised re-issue of that series.


Introduction


In this series I'm exploring the possibility of arriving at the fireworks event with only a few chemicals, some other materials, some tools and equipment, but with no completed pyrotechnic compositions, and then producing good traditional paper ball shells from scratch.

One might ask, "Why paper ball shells? Couldn't you make plastic shells, or maybe pasted or rinfasciature cylinder shells?" (A. Fulcanelli, in the often-referred-to Pyrotechnica IX and XI series on cylinder shell construction, describes rinfasciature as "a traditional method by means of which shells may be made with dry paper wrap in lieu of pasted wrap.")

I could, but I like paper shells because they employ such simple, traditional, biodegradable materials. In the long run, I think there will be fewer and fewer places where we are welcome to shoot plastic shells.

I also like ball shells for the nice, round, symmetrical breaks that are possible with them. But, of course, these are just my 'druthers.


RECAP


You may want to review the project "How to Make Charcoal" which detailed the charcoal options for this project. It included the production of homemade charcoal to be used in the various components of the shells. The charcoal-making step of the process would occur at home prior to travelling to the pyro get-together.

In "How to Use a Ball Mill Safely and Effectively", ball milling materials, skills and techniques were addressed. (Ball milling will be put into immediate action once we arrive at the site and begin actual production of these shells in this part of the series.)



Friday Morning, 8am - 9am, Arriving and Setting Up


Well, I've arrived on site at our pyro event with homemade charcoal and all the other supplies and equipment I'll need. At the end of this series of articles I'll include a complete checklist of all the materials and tools I've used in this project.

A pop-up tent is useful for shelter from the sun and possible rain. A couple of folding tables and a chair are also necessary. I like to bring an extra chair or two because the manufacturing area always becomes the place of choice for socializing and educational experiences.

If electric power is not available at the site, a small, portable generator will be required, along with a can of gas for it. In either case, a few 100' extension cords will be needed. It can be nice to barricade the sound from the generator with a sheet of plywood. (Honda makes some nice, very quiet generators, but they're not cheap.)

I organize the tools on my table, and I set up the ball mill and associated barricading in a safe, remote location.


9am - 10am, First Ball Mill Run


First of all, I am scaling this project to the production of two 8" Tiger Willow ball shells. The first manufacturing order of business will be to ball mill a batch of black powder (BP) with dextrin in it for use in the making of burst powder.

I run a 100' extension cord to the mill, plugged into a timer at an electric outlet or at the generator. I set the timer for a one-hour mill run time.

I use a small ball mill, with the jar half filled with ball milling media. This mill/media combination is very efficient, turning out very finely milled black powder in an hour. For this project I'll typically mill a 40-42 ounce batch at a time. (Please see the Ball Milling 101 article in Skylighter Fireworks Tips #91 and/or Lloyd Sponenburgh's Ball Milling Theory and Practice for the Amateur Pyrotechnician, for more information on ball milling.)

Note: Normally, as I indicated in the article on ball milling, I only charge the mill jars with 20-21 ounces of materials to mill black powder. This is the optimal charge for these one-gallon jars to achieve the most efficient milling. But, for this project, I have doubled that material charge amount to speed up the process. This produces powder whose performance is adequate for this endeavor.

I mill a batch of BP with 30 oz. of potassium nitrate, 6 oz. of homemade airfloat charcoal, 4 oz. of sulfur, and 2 oz. of dextrin.

While this batch is milling, I continue to unpack and organize my tools and materials.

When the milling is done, I separate the powder from the media using a 5 gallon bucket separation screen, inserted in another 5 gallon bucket.


10:00 - 10:30 am


I now fill the mill jar with the next 42 oz. batch of BP chemicals to be milled, put the jar in the mill, and set the timer for the second one-hour mill run. From 10:15 - 11:15 am, I run the mill for second batch.


10:30 - 11:00am, Making the Burst Powder


For single petal ball shells, I like to use black powder, coated onto either puffed rice cereal or rice hulls, for the burst. I prefer BP on rice hulls, specifically for multiple petal shells where the burst powder needs to be packed tightly into narrow spaces. I'd refer the reader to the Passfire website for detailed investigations/instructions concerning burst powders and coating various cores with them.

I'm going to coat the 42 ounces of mill-dust/dextrin onto 6 oz. of puffed rice which has been screened with a 10 mesh screen, kitchen colander to remove the dust and chaff. (I use the cheap, puffed rice cereal which comes in 6 ounce bags in the breakfast foods aisle of my grocery store.)

Sift Dust Out of Puffed Rice with Colander Screen
Sift Dust Out of Puffed Rice with Colander Screen

I use a Hobby Fireworks star roller with the original plastic drum replaced by a stainless steel pot to coat the powder onto the puffed rice.

Hobby Fireworks Star Roller and Garden Sprayer
Hobby Fireworks Star Roller and Garden Sprayer

Hobby Fireworks is now out of business. One alternative star roller that many folks use is a cement mixer with the mixing blades removed, and any holes in the drum plugged. Below is a photo of a plastic-drum mixer that I bought at Lowe's for $300. The blades easily unbolted from the inside of the drum, and I simply covered the holes with duct tape.

Star Roller Made From a Cement Mixer
Star Roller Made From a Cement Mixer

Warning: A cement mixer is a direct drive machine. It is next to impossible to stop the barrel by hand when it is turning. That is why I plugged the holes in it with duct tape. I did not want any rivets, bolts, etc., sticking out of the barrel, ready to grab my clothing. I checked the barrel to make sure it was smooth and had no projections. I have short hair and no ponytail, I wear no "bling" chains around my neck or wrists, and I donít wear loose clothing when I'm using this roller. Please be careful if you convert a cement mixer to a star roller.

Wearing gloves and a respirator, I run the star roller on medium speed, and start spraying the puffed rice with water, sprayed out of a little hand-held, garden-sprayer bottle. Once the rice is dampened a bit and starts to stick together, I add a cup of the milled BP. I alternate spraying the rice with water and adding the BP, breaking up any clumps of cereal that form with my gloved hand.

Puffed Rice in Star Roller Coating BP onto Puffed Rice in Star Roller
Coating BP onto Puffed Rice in Star Roller

As I roll the BP on, I use my gloved hand and a plastic-mesh scouring pad to continually scrape off any BP which starts to stick onto the sides or bottom of the barrel.

Keeping Roller Barrel Clean with a Scouring Pad
Keeping Roller Barrel Clean with a Scouring Pad

I slowly spray on enough water so that all the loose, powdered BP is picked up by the puffed rice.

I don't want the rice to get so wet that the kernels look glossy-wet, but I do add enough water to form a nicely consolidated shell of BP on the rice. This simply takes a bit of practice. I keep this process up, spraying water and adding powder, until all 42 oz. of the BP has been rolled onto the puffed rice. Then, with the roller still running on slow speed, I tip it forward to dump the burst granules into a bucket.

Bucket of BP-Coated Puffed Rice
Bucket of BP-Coated Puffed Rice

A bucket of water and a sponge comes in handy for washing tools, hands, and the star roller. If there is a water faucet available, a hose and nozzle are useful as well.


I have made a little drying chamber and screens which stack inside of it. Read more about how to make two kinds of drying chambers.

Learn to make a Drying Chamber and Drying Screens...

BP-Coated Puffed Rice in Drying Tray BP-Coated Puffed Rice
BP-Coated Puffed Rice in Drying Tray

I pour the coated puffed rice out in thin layers on two of the screens, insert the screens into the dryer, install the lid, and plug the heater in. The burst powder will be dry in about 12- 24 hours.

It is important to locate the dryer in a safe, protected location, as one would do with drying any pyrotechnic devices or compositions. There should be no possibility of anyone smoking in its vicinity. I also think it's a good idea to locate it in the same remote location that the ball mill is in, just in case some sort of ignition occurs.

So, now we've used the first mill run of BP to make the burst granules, and they are drying in the chamber.



11:15 - 12:30 pm, Making 36 Feet of Black Match


First, I empty the jar from the second BP ball mill run, and reload it with a 40-ounce batch which has 30 oz. of potassium nitrate, 6 oz. of airfloat charcoal, and 4 oz. of sulfur, but no dextrin in this run. This mill run takes from 11:30 to 12:30.

Half of the second batch of powder, 21 ounces with dextrin in it, is now used to make my own black match. I want to make this homemade match and quickmatch, starting this project with no pyrotechnic materials at all. The other 21-ounce half of the second batch gets set aside in a covered container marked "BP with dextrin."

Black Match and Paper Match Pipe Combine to Make Quickmatch
Black Match and Paper Match Pipe Combine to Make Quickmatch

Cotton String
Cotton String

This is the kind of cotton string that is often used for pyro purposes. It is typically found in 6/8/16/ or 24 strand string, rolled on cones as above.

I made a little match-making frame and stand that I use for small-scale black match making. The frame is sized to fit into my drying chamber once it has been removed from the stand. You'll note that the frame's cross members are half-inch aluminum tube, which I coat with a layer of wax.

The aluminum keeps those cross members from sucking the moisture/potassium nitrate out of the wet black match which will be wrapped around them. The wax keeps the black match from sticking to the rods, and prevents the chemicals from reacting with the aluminum.

Match Making Frame
Match Making Frame

Coating Cross Members with Wax
Coating Cross Members with Wax

I tie one end of the string I'm using onto one of the frame cross-members near one end, and wind string onto the frame at about 3/4" intervals.

String Wound onto Frame
String Wound onto Frame

Taking the Twist Out with a Drill
Taking the Twist Out with a Drill

This measures off about 36 feet of 12-to-24 strand cotton string. I tie one end to something stationary, unwind the string from the frame as I walk backwards, and tie a knot in the other end. I then insert that free end into the chuck on my drill, and pull the string tight while running the drill in reverse to take the twist out of the string. My goal is to end up with all the individual strands in the string lying fairly flat next to each other.

It helps if I have my lovely assistant walk the string toward me from the far end, with her hands separating the strands into two halves, as I take the twist out of the string. (My wife, Molly, is much happier to help with these projects if I call her my "lovely assistant," so I don't hesitate to do so.)

Then I wind the untwisted strands of string back onto the frame.

Untwisted String on Match Frame
Untwisted String on Match Frame

Using a paint stick and a plastic tub (about the size Skylighter uses for 5 lbs. of chemicals), I stir about 9 ounces of water into the 21 oz. of BP-with-dextrin from the second mill batch. Stir the water in slowly, and stop adding it when the slurry gets to a thick, pancake-batter-consistency. Don't make it too thin.

I slowly work the string into the slurry, starting from one end of the string, and patting the string down into the slurry a few inches at a time, unwinding it from the frame as I go. The goal is to thoroughly impregnate the string with the BP mix. I'll pat and knead the string in the slurry for 5 minutes or so, being careful to press the mass, but avoid tangling the string.

Working String into Black Powder Slurry
Working String into Black Powder Slurry

I cut a section out of the nozzle of a tube of caulk to create a little forming die to pull the wet match through as it comes out of the tub. The die removes excess slurry and regulates the diameter of the match. (I've seen video of Maltese fireworkers using a rubber baby-bottle nipple for this purpose.) I want an exit hole in the small end of the die of about 1/8" - 3/16". It's best to start out on the small side with this hole, and enlarge it if necessary.

Plastic Forming Die Plastic Forming Die with String Being Threaded Through It
Plastic Forming Die with String Being Threaded Through It

I put the end of the wet match through this die, and then tie that end onto the drying frame. Pulling the match through the die, I then wind the match onto the drying frame, revolving the frame as I go, until I get to the other end of the match. I then tie that end onto the frame, also.

Pulling Wet Black Match through Die Winding Wet Black Match onto Frame
Pulling Wet Black Match through Die, and Winding It onto Frame

Frame Full of Wet Black Match
Frame Full of Wet Black Match

I now loosen the screws which hold the frame to the stand, and put the frame into the drying chamber on top of the two screens which contain the burst powder. This match will be dry in about 12-24 hours as well.

Only 8-12 ounces of the slurry will actually be taken up by the string in the above process. But I made up 30 ounces of it because I wanted the string and match to stay nice and wet during its impregnation and pulling through the die. If less slurry is used, too much is sucked up by the string. Then the slurry gets dry, and the match becomes hard to pull through the die.

The leftover slurry can be highly diluted with water and disposed of in a safe location.


12:30 pm - 1:00 pm


Dump the third ball milled batch of BP, screen out the mill media, add another 40 oz. batch of BP chemicals into the mill (same proportions as the third batch, no dextrin), and run the mill for another hour, 12:45 - 1:45.


1:00 - 2:00 pm, Press Lift Powder


Note: There are various ways to make very satisfactory black powder for lifting shells. I have experimented with using BP-coated rice hulls, and they work just fine in the same amount that I would use of commercial 2FA.

I have also granulated BP dust, straight out of the ball mill, by adding denatured alcohol in which red gum has been dissolved (red gum = 1% of BP weight, 1 3/4 cups of alcohol for 40 ounces of mill dust). I granulate this 'putty' through a 1/4" mesh screen onto kraft-paper lined trays and allow to dry. When using BP made this way, I only have to use 3/4 of the amount that I would of commercial 2FA.

For me, so much of the fun of fireworking is this sort of curiosity, pondering, experimenting, recording and comparing results, drawing conclusions which I can use in the future, and so forth. This is science combined with the art, which I find so satisfying.

For this project, I am making the BP in a more traditional manner, making pucks and granulating them after they are dry.

I add 2 oz. of water to 20 oz. of the ball milled BP dust (half of the third mill batch, no dextrin) and knead the water into the powder thoroughly in a small bucket with my gloved hands. Then I force the dampened comp through a fine, 20 mesh-screen (a kitchen colander) to further distribute the water in the BP.

Screening Black Powder to Incorporate Water
Screening Black Powder to Incorporate Water

Below is a photo which shows a 3 1/2" comet pump from Rich Wolter with a block of aluminum to use under the pump while pressing. Also shown is a brass 2" comet pump from Skylighter.

2 Inch and 3 1/2 Inch Comet Pumps
2" and 3 1/2" Comet Pumps

I use one of these pumps, along with my 12 ton hydraulic press, to press the dampened BP dust into 1/8"-thick pucks, using about 7 tons of force on the large pump, or 5 tons on the small pump. I can press 1 1/4 ounces of BP at a time with the large pump, and 1/2 ounce with the smaller one. I apply enough pressure with the press that water starts to seep out between the comet pump and the aluminum plate.

When I add the powder to the large comet pump, with the sleeve sitting on the aluminum block, I use a small dowel to distribute the powder evenly at the bottom of the pump sleeve so that a nice puck of even density is produced.

I add the BP to the small comet pump while holding it upside-down, and lightly press the powder into the pump so that it stays in place when I turn the pump right-side-up.

Distributing Black Powder in Large Comet Pump Distributing Black Powder in Skylighter Comet Pump
Distributing Black Powder in Comet Pumps

Pressing Pucks with a Hydraulic Press
Pressing Pucks with a Hydraulic Press

Note: It is possible to hand-ram the powder in the brass pump to consolidate it, using a pounding-post, a cutting board, wax paper, and a rawhide mallet. The pucks that are made this way will not be quite as dense as the ones made with the hydraulic press, but they ought to be quite usable, nevertheless.

Hand-Ramming Black Powder Pucks Finished Black Powder Pucks
Hand-Ramming Black Powder Pucks

Black Powder Pucks on Drying Screen
Black Powder Pucks on Drying Screen

I place my finished pucks on a drying screen, and place it in my drying chamber.

I want to end up with 6 oz. of 2FA BP for each 8" shell, for a total of 12 ounces. I have determined that after the pucks are dry and I crush them I will end up with about a 60% yield of 2FA sized particles, with the rest being a finer powder. Based on this I should end up with about 12 oz. of the 2FA from the 20 oz. batch which was just pressed into pucks.

A note on presses: I use two presses that I bought from Hobby Fireworks, a 4 ton and a 12 ton. But since Hobby Fireworks is no longer in business, you might want to look online at the various shop presses available at places like Harbor Freight, Northern Tool, or Greg Smith Equipment. There is a very nice 12 ton hydraulic shop press, with a pressure gauge and lots of adjustability, available at Greg Smith for only $159. That is the type of unit I'd be looking at for a starter press.

Greg Smith 12 Ton Press
Greg Smith 12 Ton Press

A ball mill, a star roller, and a hydraulic press, are the 3 basic machines that are very useful in this hobby.


2:00 - 4:00pm, Pressing Stars


I've formulated a star comp, which is halfway between Tiger Tail and Willow, which I refer to as Tiger Willow. I've further modified this comp by replacing 5 of the airfloat charcoal percent in the formula with lampblack, which increases the sparks' hang time. The lampblack can be replaced with the original, equal amount of charcoal if desired.

My adjusted comp is as follows, using the 60 ounces of BP mill dust (half the third, and all of the fourth batches, which had no dextrin in them).

Tiger Willow Star
Component Weight
BP Mill Dust 60 oz.
Homemade airfloat charcoal 36 oz.
Dextrin 8 oz.
Sulfur 4.2 oz.
Lampblack 5.7 oz.
   
Total dry weight 113.9 oz.


I screen all the ingredients through a 40 mesh screen, and mix them thoroughly in a 5 gallon bucket with a tight lid. Then I screen them all together one more time and shake them in the bucket again. 14 ounces by weight of 3/1 water/denatured alcohol is blended into the comp, first with gloved hands, and then by screening the comp through the 20 mesh screen. This produces a slightly dampened, fine flowing composition.

I press the stars using a star plate from Rich Wolter, which produces 49 three-quarter inch stars at a time, with all 12 tons of force from my press. It takes a bit of practice to evenly fill the plate, tamp the comp down with the pin plate, fill it again, tamp it down again, and fill it to the top one last time, before the final compaction in the press.

Loading Composition into Star Plate (on Aluminum Plate)
Loading Composition into Star Plate (on Aluminum Plate)

Pressing Star Plate in 12-ton Press
Pressing Star Plate in 12-ton Press

The goal is to produce 3/4" long, 3/4" diameter stars of equal density. The stars are then stacked on drying screens and placed in the dryer.

Stars Ready for Drying
Stars Ready for Drying

Note: As an alternative to pressing the stars with the relatively expensive star plate and hydraulic press, a smaller, less expensive Skylighter star plate can be used. This plate produces a dozen 9/16" diameter stars at a time.

While this diameter is a bit smaller than the 3/4" stars produced by the above method, the stars can still be rammed 3/4" long. The amount of composition that was mixed up would still all be used, but more stars would be made in this smaller size.

This plate can be used with the mallet, cutting board, wax paper, and a pounding post.

Skylighter Star Plate
Skylighter Star Plate

Loading Star Plate with Comp
Loading Star Plate with Comp

Ramming Stars Ejecting Stars
Ramming and Ejecting Stars

Once you get going with this method, stars can be knocked out fairly quickly.


The Day's Results


So, I've worked from 8am to 4pm, and have produced burst granules, black match, black powder pucks, and stars. All of these are busy drying in the drying chamber. The ball mill, star roller, and hydraulic press have all been put to good use. Now I'm free to clean up a bit, using a sponge and 5 gallon bucket of water, and sit around and tell exaggerated pyro stories with my pals. All in all a very good day.

Tomorrow I'll be granulating the BP pucks, priming the stars and drying them a bit more, making spolette fuses for the shells, and assembling the shells. Finally, the shells will be pasted in for an overnight drying.

Until next time,
Rest Easy and Stay Green,

Ned

Materials Needed
Read and review these Fireworks Safety Articles before starting any fireworks project.

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