Here’s your link for Turbo Pyro:

http://www.turbopyro.com

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I DON’T KNOW WHETHER YOU HEARD THIS YET
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I’ve added *more* stuff to Turbo Pyro. I want to make sure you have fun with your projects, so I added a bonus Smoke Bomb Kit and project–Making Jumbo Smoke Canisters eBook (including videos).

Be sure and get online fast and place your order. Again, there are only 400 Turbo Pyro Supplies Kits available.

Grab yours here:

http://www.turbopyro.com

P. S. You get instant access to the Turbo Pyro eBook and the Smoke-Making eBook right after you order.

P. P. S. Be sure ahead of time your credit card has enough $$ left on it to make the charge. Otherwise you may miss out. (V, MC, Amex, Disc.)

Harry

Turbo Pyro goes LIVE at 12:00 Noon Eastern time today, June 19th is a post from: Confessions of a Fireworks Man

In Making Gerbs (Firework Fountains)I described a method for making homemade fountains, called gerbs, including how to make the tools for ramming them. In Using Homemade Gerbs Creatively I explored a few creative devices using fountains.

I was ready to move on from gerbs, but then I received a note from Paul N, a loyal Skylighter customer. In his letter, he began by referring to his homemade waterfall, in which he used consumer fountains, a trick I described in Consumer Fireworks Display: Firework Waterfall, Firecracker and Star Set Pieces.

In part, Paul said:

I of course did not relay this message to Harry, lest he get an even bigger head about the service he provides to us pyro fanatics. I could sure relate to Paul’s enthusiasm and inspiration. How often I have felt that same way.

I have never seen colored consumer fountains at local shops that might be used in the way that Paul envisions.

I like to use colored fountains as one of the stages in devices like wheels and girandolas (horizontal flying wheels). Just recently I was giving some more thought to homemade colored gerbs, and had dug out a past PGI Bulletin article by John Glasswick, entitled Gerb Colours.

John is a friend of mine and a master pyro craftsman, his gerbs and wheels are something to see. We see one another just once a year at the PGI conventions, and we have often competed against each other with our wheels or ground displays. It has been no disgrace to have him beat me in a competition, and it’s been a real honor the few times I’ve edged him out in points.

John hails from Canada, and spells words funny, like colour and splendour, but we won’t hold that against him. He graciously allowed me to use the information in his article as the foundation for this one. In that essay, John relates that he got many favorable (favourable) comments about the colors of his gerbs one year at the convention, along with quite a few requests for his formulae.

John started with a favorite red formula that had been shared by Tom DeWille on the Pyrotechnic Mailing List several years back. This red formula was slightly modified to create the other colors, with one exception; blue.

The blue composition came from Joel Baechle’s Pyrocolor Harmony, to which John added 15 parts titanium for sparks. About that book, John states, “I found Joel’s book well worth purchasing, and the book has also been invaluable for me for star colour formulas.”

Note: There is another nifty blue gerb formula and method described by Mr. Gilliam in the Fireworks Tips #52 article, Blue Steel Gerbe.

So, rather than quickly moving on from the subject of gerbs, why don’t we spend one more week on them, and explore color gerbs.

The following are the formulae from John’s article, as well as Joel Baechle’s blue composition, to these formulae John added 13% titanium. I use either fine spherical titanium such as CH3010, which produces a short, dense spray of fine sparks, or the coarse spherical Ti such as CH3001, which produces a long spray of larger silver sparks.

If you want a simple colored flame with no silver sparks, the titanium may be omitted completely. It could also be replaced with ferro-titanium if less brilliant, yellow-silver sparks are desired, or even coarse charcoal for a softer, orange spark spray.

Green Gerb Composition
Same as above except substitute barium nitrate for the strontium nitrate.

Note: I ended up using only these three basic color compositions. Other colors were made by combining these comps in various ratios as described later on.

I will include John’s other formulae, though, as listed below:

Lime Gerb Composition
Same as green except use 0.43 barium nitrate, and 0.01 sodium nitrate.

Some notes concerning these formulae:

• Strontium nitrate and sodium nitrate are hygroscopic, which means they will readily absorb moisture from the air. They should be stored in tightly sealed containers, and dessicant packs stored with them will help keep the chemicals dry. It can be helpful to dry the chemicals prior to using them, by spreading some of the chemical out on a kraft-paper-lined cooking sheet and heating it in a 200-degree oven for 2 hours.

  Warning: I repeat, this oven-drying is only done with these individual chemicals, never mixtures.

  Once gerbs are made using either of these chemicals, they should be burned in short order or they should be stored in tightly sealed containers (ziplock baggies work well) with some dessicant packs.

• Barium compounds are toxic, and simple precautions such as wearing gloves and a respirator will prevent them from being absorbed through the skin or lungs. Some folks are very sensitive to barium, and I’ve heard tales of those who have suffered its poisoning. It does not sound like fun.

• Some folks substitute saran for parlon with good results.

There is an article, Lancework – Pictures in Fire, by the Kosankes, in Pyrotechnica XV, which contains formulae for lance. The authors begin with red, green, and blue compositions and then combine those three powders in the following ratios to create other colors:

Yellow – 0.25 red, 0.75 green

Orange – 0.60 red, 0.40 green

Chartreuse – 0.14 red, 0.86 green

White – 0.14 red, 0.28 blue, 0.58 green

Purple – 0.60 red, 0.40 blue

Aqua – 0.25 blue, 0.75 green

Similarly, the Veline color star formulation system, found in Tom Peregrin’s Introductory Practical Pyrotechnics, starts with four basic color compositions, red, green, blue and orange, and mixes them to obtain other colors:

Yellow – 0.45 orange, 0.55 green

Chartreuse – 0.20 orange, 0.80 green

Aqua – 0.20 blue, 0.80 green

Maroon – 0.85 red, 0.15 blue

Salmon – 0.25 red, 0.60 orange, 0.15 blue

Purple – 0.15 red, 0.05 orange, 0.80 blue

I’ve always found it interesting that these basic color comps are not combined in the same combinations that paints would be. They are rather mixed so that the light they emit combines to give the appearance of a completely different color. I used these color-combining methods to achieve the other various colors of gerbs using the basic color compositions: red, green, and blue.

In his article, John states, “I have found the compositions difficult to ignite, but I have had no problems as long as they are primed with a 50:50 mix of black powder/gerb composition.”

In the Making Gerbs article, I described a Starting Fuel composition. I rammed one increment of this fuel before introducing any standard fuel, especially in gerbs where I was going to be drilling the nozzle aperture with a twist-drill. This prevents sparks during that drilling.

This Starting Fuel is perfect for priming the gerbs as John describes. The first rammed increment above the nozzle will be Starting Fuel. The second increment will be 50:50 Starting-Fuel/gerb-composition. Then increments of the colored gerb composition will be rammed.

This is called “step priming”, and is a common practice, especially when rolling round stars, when a low-temperature composition is going to ignite a high-temperature one.

This will work well to ignite our color gerbs, with one big exception. No composition containing ammonium perchlorate may be in contact for any length of time with a composition containing potassium nitrate, such as the Starting Fuel or any other standard black powder composition.

This is because the combination of potassium nitrate and ammonium perchlorate forms extremely hygroscopic ammonium nitrate within a short amount of time. If you try that combination, you’ll soon end up with a soggy mess which will not burn.

You might try standard priming if you’re going to ram your blue fountain and take it right out and burn it.

But, with the blue gerb comp which contains ammonium perchlorate, or any color mixture which contains that composition, we have to have a different first-fire/priming mixture if the gerbs will be stored for any length of time.

This composition will be used to ignite the ammonium perchlorate containing gerbs in the same step-priming fashion described above.

For simplicity, it actually can be used to prime any of these color gerbs.

For this project, I want to make several of each type of gerb in the basic colors, and I want to try mixing the basic compositions to form the other colors. So, I want to mix up 16 ounces of each of the red, blue, and green formulae for starters.

I think I’ll make up those basic mixes without the titanium in them. I can then see what they look like with just the colors, and then I can add the Ti to the mix for individual gerbs to see how they look with that metal in them.

Many of you may know this, but there is a nifty way to remember the basic colors of the rainbow: Roy G. Biv: Famous pioneer in paint coloration. Well, maybe not.

Red, Orange, Yellow, Green, Blue, Indigo, Violet (Indigo is the bluish purple, and Violet is the reddish purple, and I usually just lump them together as purple when I think of the rainbow.) ROYGBIV

So, I want to make a rainbow of colored gerbs.

To make a 16 ounce batch of one of the formulae, I take the decimal ratio of each individual chemical, and multiply that decimal by the final batch size to arrive at the amount of that chemical to use. For example:

0.44 x 16 = 7.04 ounces of strontium nitrate

0.17 x 16 = 2.72 ounces of parlon

0.17 x 16 = 2.72 ounces of magnalium

0.13 x 16 = 2.08 ounces of titanium

0.09 x 16 = 1.44 ounces of red gum

Total = 16 ounces

(My little digital scale weighs to the nearest 0.05 ounce, so I round the above amounts to the nearest 0.05 ounce, to get 7.05, 2.7, 2.7, 2.1, and 1.45 ounces, respectively.)

I then add all the individual chemical amounts together to make sure that the total is about 16 ounces (may vary a bit due to number rounding). In this case the total comes to exactly 16 ounces.

After weighing the chemicals out individually, I screen them one at a time through a fine-mesh kitchen colander, into a bucket. I check the weight of the complete composition and make sure it is very close to the original total batch weight I wanted. This ensures that I didn’t miss a chemical, and that I weighed each one accurately.

Note: If, during the screening, I discover that any of the individual chemicals won’t pass the screen, I mill that single component in a small coffee grinder until it is very fine. I have a mill that is dedicated to fuels, and one that is used only on oxidizers. I never put metals into any of the grinders.

I put the lid on the bucket and shake it a bit, to thoroughly mix the contents. Then I gently screen the mix one more time through the colander to break up any remaining clumps of chemical.

I did not granulate these compositions. I did use rubber o-rings on my tooling drifts to keep the loose comp from fluffing out when the tooling was inserted into the tubes.

A few more tips from John Glasswick’s article will come in handy now.

He does not press his gerbs, but simply compacts the compositions with his body weight on the tooling. Since the nozzle clay really holds up best when it is solidly compacted, I decided to ram the nozzle as I usually do, with 12-16 rawhide mallet blows. I used bulkhead mix without any grog in it since I plan on hand-drilling the hole in the nozzles.

After the nozzle was rammed, I started with a flat half-tablespoonful of the starting fuel, and consolidated that increment with 8 light hits with the mallet. I followed the starter fuel with an increment that consisted of 1/2-teaspoonful of starter fuel mixed with 1/2-teaspoonful of gerb composition. I simply mixed these fuels in a paper cup with a gentle swirling motion before introducing the mix into the gerb tube.

Note: Since I’m ramming the blue composition which contains ammonium perchlorate, and I’m planning on mixing that comp with other colors to produce color-mixes, I actually just used the potassium perchlorate first-fire composition for the priming of all the gerbs I made for this project.

Then I rammed increments of gerb fuel and finished off with a clay bulkhead, just like any standard gerb. I rammed all of these increments with the same 8 gentle drops of the rawhide mallet.

Note: One of the reasons John does not pound on his compositions is that they contain sponge titanium which he uses. Rough metals like that can cause sparks when they are hand rammed with a mallet. I’m using smooth spherical titanium, and I consider this to be safer to hand ram, although I am using gentle hits when I do this with these formulae. It is best to do this outdoors with no large quantities of exposed compositions just in case any accident occurs.

John notes that he uses thicker walled tubes for these gerbs because they burn hot and can burn through the walls of thinner tubes. I used 1/4-inch wall tubes throughout these gerb projects.

And, finally, because these compositions have magnalium in them, among other ingredients, they produce dross or slag when they burn. This dross can tend to clog a narrow nozzle aperture, so the holes that we’ll drill in these nozzles will be on the large side. For these 3/4-inch ID tubes I’m going to drill 3/8-inch nozzle holes. 5/16-inch ones might work, too, and would produce a bit more thrust and a higher spray of sparks.

• Blue

  I rammed a gerb in a 7.5-inch tube using the blue composition, without any titanium in it. It ate up 1.9 ounces of the blue composition, and once the starting fuel increments burned, it produced a really nice blue flame about 10-inches long. The fountain burned for one minute.

  The same gerb, using 1.75 ounces of blue comp and 0.25 ounces of titanium, mixed in a paper cup prior to ramming, burned exactly the same except it also produced a nice 6-foot tall spray of bright silver sparks.

  

  Blue Gerb Without Titanium

  Note: I am not cropping these gerb photos so that you can see their relative brilliance by comparing how much of the surroundings light with each one.

• Red

  I rammed a red gerb in a 7.5-inch tube, without any titanium in it. It took 2 ounces of the composition to do this. After the first-fire increments burned, a brilliant 8-inch red flame spouted forth for 60 seconds. But, the tube sidewall did burn through for the last 10 seconds and a lot of the flame started spewing sideways out of that enlarging hole.

  The gold-glitter and silver-titanium gerbs I made a couple of weeks ago only burned for about 30 seconds, so I could settle for a 30 second burn with these color gerbs as well. To accomplish that, looking at the sketch of a gerb and noting that the actual fuel grain in the 7.5-inch tubes is a little over 5 inches long, I could start with half that fuel grain. This would result from ramming the gerbs the same way, but starting with a 5-inch tube.

  A red gerb in a 5-inch long tube, rammed with 1 ounce of composition, burned for exactly 30 seconds, with no tube sidewall burn-through. It’s hard to overstate the brilliance of these red gerbs. Man, they are fierce!

  My assistant in these comparisons was my granddaughter, Michelle, and the red gerb was her favorite by far.

  I added 0.15 ounce of titanium to 1 ounce of the red comp and rammed that in a 5-inch tube. That gerb burned identically to the one above, but with a 6-foot spray of silver sparks. Very nice.

  

  Red Gerb Without Titanium

• Green

  Since the green gerb composition simply replaces the red’s strontium nitrate with barium nitrate, I expect it to perform similarly to the red. (Famous last words.)

  So I’m going to try 1 ounce of the green comp in a 5-inch tube. (It actually only took 0.75 ounce of the comp.) This gerb burned with a brilliant green for exactly 30 seconds, with no tube burn-through.

  0.10 ounce of titanium added to the 0.75 ounces of green fuel produced the same effect, with the addition of the silver sparks.

  

  Green Gerb Without Titanium

• Yellow

  For starters, I thought I’d try something simple to produce a yellow gerb: a combination of the red and green comps I already had mixed up, in a 0.25/0.75 ratio, as the Kosankes recommend with their lance method.

  So I took 0.25 ounce of the red comp and 0.75 ounce of the green and mixed them together. That mixture got rammed into a 5-inch tube, and I had 0.10 ounce of the mixture left afterwards.

  That gerb burned with a brilliant yellow flame, similar in brilliance to the red and green gerbs. I did notice a bit of a green tint around the edges of the flame, so I tried one with 0.30 red and 0.70 green to see if I could balance it on the yellow a bit better.

  I did like the more pure yellow color of that mixture better.

  

  Yellow Gerb

• Orange

  Yellow worked, why not try the Kosanke proportion for orange: 0.60 red/0.40 green.

  A 5-inch tube, burned with a brilliant orange flame for 30 seconds. The color looks more like red in the photo and video, but the gerb definitely had a brilliant orange color to it.

  

  Orange Gerb

• Purple

  One more color to try out. I prefer a purple that leans toward the blue end of the spectrum: an indigo. So rather than try the Kosanke 60/40 red/blue, I thought I’d try something more along the Veline proportion: 0.20 red/0.80 blue.

  Oh, man, really nice 30 second purple fountain tending toward the blue end of the spectrum, just like I like it.

  

  Purple Gerb

5/16-Inch Nozzle Aperture

I decided to try out my standard gerb tooling which automatically forms a 5/16-inch hole in the nozzle, rather than hand-drilling a 3/8-inch hole in a solid nozzle. This should increase the pressure inside the tube during the burn, and also increase the possibility that the dross formed by the burning fuel will clog the nozzle as it burns.

I used a 5-inch tube, 0.75 ounce of the red fuel to which I added 0.10 ounce of 36 mesh charcoal. This gerb burned for 30 seconds with a flame that was similar to the gerbs with 3/8-inch nozzle holes. It did produce a nice, soft, 5-foot tall spray of orange sparks which did not detract from the brilliance of the red flame.

Note: One more time, remember to begin each gerb with an increment of the starter fuel, and then one of 50/50 starter fuel/gerb composition.

Well, I have ways to make each of the 6 colors of the rainbow in brilliantly burning 30-second gerbs: Red, Orange, Yellow, Green, Blue, and Purple.

These colors, and other possible combinations, all start with only 3 basic color compositions: Red, Blue, and Green. I really have to try Aqua, one of my favorite colors, and then there’s chartreuse. What color is chartreuse, anyway?

And, if I want to I can make a blue fountain that burns for 60 seconds. (I suspect it is the magnalium in the other mixes which burns so hot that tube burn-through begins at 45-50 seconds with them.)

I can add the titanium to the compositions for a tall spray of silver sparks, or the gerbs can be burned with only the brilliant colors illuminating everything around them.

These fountains will make great additions to wheels and girandolas, and in the back of my mind I can imagine them lined up on a frame, shooting their flames on an angle, and creating designs and letters with them.

So many projects, so little time.

Paul, I hope the red and blue gerb compositions fit the bill for the “idea” you have in mind for your next backyard-waterfall project. Michelle’s favorite color is the red, and mine is the blue with the gentle orange charcoal sparks.

Thanks to Tom DeWille, Joel Baechle, and John Glasswick for blazing a path which we can follow when creating these beautifully colored flames.

Stay Green, and red, orange, yellow, blue, and purple, too.

Ned

Colored Gerbs is a post from: Confessions of a Fireworks Man

After talking for the past few weeks about all the interesting things we can do with commercially-made consumer fireworks, let’s now make some simple, easy-to-make display items of our own.

In a past article I wrote about making nozzles and bulkheads. We’ll be putting those lessons to work in this article.

In Making Your Own Firework Tubes I explored cutting, treating, and rolling paper fireworks tubes. These tubes will also be used in this project.

Homemade fountains, called gerbs by pyro-folks-in-the-know, are very versatile devices. They can be used as stand-alone fountains shooting sprays of sparks skyward, as drivers on wheels, as downward spraying tubes in a homemade waterfall, or as line rockets.

I’ll be demonstrating those line rockets, sometimes called rats or pigeons, in the post following this one, so stay tuned. I’ll also be using these fountains as drivers on a fireworks wheel. I described using commercial cone-fountains to drive one of these unique Chromatrope double-wheels in Mortar Racks, Fusing Techniques, and a Firework Wheel.

Devices very similar to these fountains, employing a slightly faster-burning fuel and a somewhat different nozzle configuration, were what I described in the How to Make End-Burner Rocket Motors. In that article I showed how gerbs can be used to create a design, called a gerb set-piece.

From Wikipedia: A gerb is a type of firework which produces a jet of sparks, usually from 15 to 60 seconds. It is a thick-walled tube filled with pyrotechnic composition and possessing a choke, which is a narrowing in the tube. Gerbs are often referred to as “fountains.”

I don’t know what the origin of the word “gerb” is, but I learned, while trying to find out, that there is a Star Wars race of the same name. Interesting.

The word is pronounced the same as “germ” but with a “b” instead of the “m.” I wouldn’t want to saunter up to a group of pyros, trying to appear experienced in the ways of fireworks, and say “gerb” as in “Gerber” baby food, now would I?

Gerbs are one of the most simple of fireworks, but they offer the opportunity to learn some basic fireworking skills, and also to get in the habit of practicing basic safety precautions.

I’ll be using a 1/4-inch wall, 3/4-inch ID, 7-1/2-inch long, paper fireworks tube in this project: Skylighter tube #TU1068, or cut from #TU1065.

This size tube, 3/4-inch ID, and the rockets and gerbs that are made with it, are traditionally referred to as “one-pound” tubes and devices.

I have treated the tubes with Minwax Wood Hardener, and have allowed them to dry completely.

I have made some clay nozzle mix, and also some bulkhead mix, as described in a previous article.

In the Skylighter Project Plans
article, How to Make Saxon Fireworks Wheels by John Werner, two fuel formulae are included. I have used these compositions for saxons, stars, and gerbs, and they are among my favorites.

I have slightly modified the two formulae so that they use only readily available chemicals.

(For the Antimony Trisulfide, either Chinese Needle or Dark Pyro may be used.)

(For the Titanium, either the fine (CH3010) or the coarse (CH3001) metal may be used. Each one will produce its own unique effect. The fine will produce a short, dense spray of small sparks. The coarse will produce a longer spray of fewer, large sparks. In this project I am using the coarse titanium.)

Each gerb will use about 3 ounces of fuel, and I plan on making about 24 of each type of gerb for use in these projects. So I am going to make 72 ounces of each formula.

To make smaller batches, simply multiply the ratio amount of each component by your final batch size to determine how much of each chemical to use. For example, if I want to make a 12-ounce batch of the gold glitter comp, I determine how much potassium nitrate to use by multiplying 0.49 x 12 and get 5.88 ounces (which I’ll round off to 5.9 ounces).

The two fuels above will be all I need if I am using tooling which forms the nozzle aperture as I ram the gerb. But, if I am using tooling which forms a solid nozzle in which I then make a hole with a twist-drill for the aperture, I want to ram a first increment of fuel which has no metal included in it. This eliminates the possibility of creating sparks with the drill.

I only need a small batch of this starting fuel because I’ll only be using one increment of it in each gerb.

After weighing out the individual chemicals for one of the fuels, I screen the potassium nitrate, sulfur, and charcoal together through a 40-mesh screen, four times. I never put any chemicals like the antimony sulfide, magnalium, or titanium through my good screens because the metals will clog the holes in my screens, and future compositions that get screened could end up with some of the metals in them.

Then I put the screened composition into a bucket for which I have a lid. I screen the remaining chemicals through a fine-mesh-screen kitchen colander, allowing them to fall into the bucket, too.

Then I put the lid on the bucket and shake it for awhile to thoroughly mix the ingredients.

I add enough denatured alcohol (available in the paint department of stores like Home Depot) to form a workable putty with the consistency of bread dough. The glitter batch required 20 ounces of the alcohol by weight. The titanium batch required 16 ounces, and the starting fuel batch took 2.4 ounces. No water is used when making these dampened compositions.

The putty is then screened through a 1/4-inch mesh screen onto a kraft paper lined tray. I’ve made a framed screen which fits nicely into some kraft-paper-lined metal cookie sheets.

After granulating the putty through the screen, I spread the granules out evenly with a coarse-toothed comb and allow them to dry thoroughly.

Note: This alcohol-granulation step greatly reduces the dust that gets produced during the following ramming operation. It produces soft, relatively dust-free granules which will crush easily during the ramming to form a densely consolidated fuel grain.

Skylighter sells one-pound gerb tooling, #TL1110. I have a set of gerb tools that is very similar to that one.

Note: You can see the rubber o-rings that I keep on my rammers. These keep dust from easily fluffing out of the tube as the rammer is inserted.

It is possible to make your own gerb tooling. I start out with two, 4-inch diameter discs cut out of 3/4-inch plywood (or these can be square). I also cut some lengths out of a piece of 3/4-inch diameter oak wooden dowel.

I started by drilling a 3/4-inch hole, 1/2-inch deep into one of the plywood discs. Then, using the same centering hole, I drilled a 1-1/4-inch wide, 1/4-inch deep, recess in the disc.

The two plywood discs are glued together, and a 3/4-inch piece of the dowel is glued into the hole of that same size. This assembly is allowed to thoroughly dry.

I’ve cut two 9-inch lengths of the dowel to make the rammers. I leave the one rammer flat-ended, with the ends sanded smooth. I bevel the end of the other rammer at a 45-degree angle except for the center 1/4 inch, using my belt sander.

The convergent angle that is formed on the top of the nozzle by this beveled former helps direct the hot gasses out of the aperture and reduces burn-through of the tube side-wall.

I use aluminum foil duct-tape to cover the flat top of the base nipple and the end of the flat bottomed rammer so that they don’t stick to the clay or fuel as they are being rammed.

It is also possible to make longer-lasting rammers out of aluminum rod.

The only additional tools I’ll need for this project are a solid post on which to pound the gerbs, a rawhide mallet, a funnel, and some measuring spoons. I’ll also use a drill bit to hand-twist-drill the nozzle aperture.

I ram devices on a 6x6x36-inch piece of treated pine, which absorbs the shock nicely without bouncing.

A rawhide mallet transfers all of its force to the rammers, whereas a rubber hammer would bounce off and would not be nearly as effective.

The first step in the actual process of making gerbs is to place the paper tube onto the tooling base, and ram the nozzle clay. I place a mark on the nozzle end of the tube because once the completed gerb is rammed it will be difficult to tell the nozzle end from the bulkhead end.

As you can see in the sketch of the gerb, I want the actual throat of the nozzle to be about as high as the tube ID, or 3/4 inch in this case.

I mark my nozzle-forming rammer with a Sharpie at the point where the top of the tube will be when the rammer is inserted far enough to be sitting at the top of such a nozzle.

Then I experiment with introducing and pounding enough clay to form that 3/4-inch tall nozzle. In this case, 0.5 ounce (a flat tablespoonful) of the bulkhead clay created just the right nozzle thickness once it was rammed.

I used 16 moderate blows with the mallet to ram/consolidate the clay. A very slight bulge in the tube where the nozzle is pressed is good; you can see in the sketch that perfection is when you ram the nozzle and bulkhead so that they slightly bulge the tube wall. This locks them into place and helps them withstand the extreme gas pressures of the burning gerb. But obviously I don’t want to apply so much force that the tube is damaged or splits.

I’ve been pounding nails with a hammer just about all my life, so it comes naturally to me. It pays to take some time to practice swinging the mallet smoothly and with consistent blows, and it is an acquired skill which will pay off handsomely once it is mastered.

If I am forming a solid nozzle that I’ll have to drill into to form an aperture, I use the bulkhead clay mix which has no grog in it. Any grog in the mix would prevent me from being able to do such drilling.

If I am using tooling which forms the aperture (no drilling required), then I use nozzle mix which has the grog in it. This mix is less susceptible to erosion during the burning of the gerb.

Now I want to press my fuel grain in the paper tube on top of the formed nozzle. I place a mark on my flat-ended rammer where the top of the tube is when that rammer is inserted all the way to the top of the nozzle’s beveled edge. Then I put more marks on the rammer every 1/2 inch below that first mark.

The last mark is 1 inch from the lower end of the rammer. That marks the top of the last fuel increment.

I want to ram the fuel in half-inch increments so that they are very solidly consolidated. Very slightly rounded half-tablespoons-full of the fuel produces increments of that size in these tubes.

If this is a gerb in which I’m going to have to drill the nozzle aperture, then the first increment of rammed fuel is made with the starter mix which has no metal in it.

Note: I measure out about 3 ounces of the fuel into a paper cup, and this is the only exposed composition in my work area as I work. I keep the rest of my compositions in tightly capped containers. Minimizing this kind of exposure can save my life in case of an accident. I wear safety glasses while I work. I consider it to be safe to hand-ram the fuel with the spherical titanium in it, but I would not do so with a rougher, sponge-type titanium.

After that starter increment, I ram increments of the standard fuel until I reach the last mark, which leaves a 1-inch empty void in the tube. I use 8 moderate blows of the mallet to consolidate each increment of the fuel. Again, I try and repeat these blows with the same force each time in order to produce consistently burning gerbs. If I don’t, my gerbs will burn with differing degrees of power-sometimes producing a high spray, then dropping down lower. I want all my gerb’s to burn the same.

I now ram one increment of the bulkhead clay, which fills 1/2 inch of that void, and leaves the last 1/2 inch of the tube empty.

Note: One secret to really effective gerbs is to ram about 1/8 inch of black powder, similar to FFg sporting grade powder, in between the final fuel increment and the clay bulkhead. When the gerb burns to that point, the black powder burns almost instantaneously, producing a “bounce” which finishes the gerb off dramatically, leaving no doubt that it’s done.

The commercially made gerb tooling that I have automatically forms a 5/16-inch nozzle aperture. If I have pressed a solid nozzle with homemade tooling, I use a 5/16-inch drill bit, gently twisted into the nozzle by hand, to form the hole in the rammed nozzle clay. I let the drilled-out clay fall back into my tub of clay mix because it’s just fine to re-use it. I drill until the bit is just through the clay and into the starter fuel.

As you’ll see a bit later in this essay, it is also possible to use different size drill bits to vary the size of the nozzle hole. This also changes the thrust of the gerb, the height of the spray of sparks, and other aspects of the effect.

I then take some Chinese Visco fuse, double over about 1/2 inch of it, making a little “V” on one end of it, and insert that doubled end into the nozzle hole. I like the Chinese Visco, as opposed to the American, for lighting rockets and devices like these gerbs because it throws out a tremendous amount of sparks as it burns. As a result, it lights things very reliably.

The gerb is now ready to be stuck in the ground, taped to a stake, or inserted into a wood base with a drilled recess, ready for ignition.

These gerbs, made with either fuel, burn for 20-25 seconds. The glitter fuel produces a graceful, soft, golden spray of popping glitter globules. The titanium fuel produces a forceful, bright spray of silver sparks.

I have to say that even after almost 20 years making fireworks I still get excited when I make one of these devices, take it out into the field, and light the visco, waiting to see how it performs. I suppose it’s the one activity I’ve never lost interest in.

I won a PGI gerb competition a few years back with a pair of 1-1/2-inch ID gerbs. I carefully weighed out alternating increments of the glitter and titanium fuels, so that the pair burned with simultaneous pulses of the bright titanium sprays alternating with periods of the soft glitter plumes. Then I ended both gerbs with dramatic “bounces.” I was very pleased with the fountains and apparently so were the judges.

The final resulting pressure at which a gerb burns is determined by the power of the fuel and the size of the nozzle aperture. With a given fuel, the pressure and height of the spray can be adjusted by changing the size of the hole in the nozzle.

A large hole, or no nozzle at all, will result in a low pressure, short spray, and the fuel will burn relatively slowly. When these fountains are hung in a line, upside-down, to create a waterfall, this sort of slow, graceful, low pressure burning is desirable.

A smaller aperture will result in high pressure, tall spray, and faster burning of the fuel. Too small a hole will result in the strength of the nozzle or tube being exceeded, and the tube will violently rupture or the nozzle will be blown out of the tube.

So within certain limits the size of the drill used to make the nozzle aperture can be adjusted and the burn of the resulting gerb can be observed and noted.

This is all just part of the fun of making firework. In my playing around, I found that the glitter gerbs work very well with 1/4-inch to 5/16-inch nozzle apertures, burning for 25 seconds. With a 3/16-inch hole, the gerb burned 3-5 seconds faster with more thrust, and the glitter effect was almost completely lost.

The titanium gerb results were: 5/16-inch aperture – 20 second burn with about an 8-foot tall spray; 1/4-inch aperture – 20 second burn with a 10-12-foot tall spray; 3/16-inch aperture – 16 second burn with an impressive 16-foot tall spray.

Here’s a link to a video of a glitter gerb, a titanium gerb, and a pulsing gerb.

A 1/4-teaspoon “bounce” increment of FFg sporting black powder produced a very impressive final “thwump” at the end of the gerb’s burn.

Next time I’ll use these gerbs to drive wheels and line rockets. They can also be used, hanging upside-down, to create a waterfall/rain-shower effect.

‘Til then, stay green and have fun,

Ned

Making Gerbs (Firework Fountains) is a post from: Confessions of a Fireworks Man