How to Make Go Getter Fireworks Shells
"Go Getters" are an animated type of star, usually seen in aerial shells, sometimes in mines. Go Getters appear to "swim" all over the sky. The animated effect is similar to flying fish fuse, but much larger and brighter. Go Getters are the most consistent crowd pleaser of any aerial effect I have ever seen.
As far as we know Go Getters were invented in the US by amateur fireworks makers in the early 1980's (if anyone knows otherwise, please correct me).
Go Getters were first described by Troy Fish in Pyrotechnica VII in 1981. In 1989 Dave Johnson published a booklet called "Go Getters," which further developed the Go Getter effect. Joel Baechle's 1989 book, Pyrocolor Harmony, contained a reference to a star formula which could make a good Go Getter. Up to that point, most, if not all Go Getters used magnesium as the fuel.
This was the base of information that existed out there in the universe when John Driver decided to make Go Getters. I first saw 6-inch blue, Go Getter shells that John had made in 1995 or 96 at a Florida Pyrotechnic Arts Guild (FPAG) event, and instantly fell in love with them. John first published his findings in the FPAG newsletter, The FirstFire, I went to one of his seminars on making them. Later a revision of the Go Getter article appeared in American Fireworks News and Best of AFN IV.
John went on to commercially manufacture Go Getter shells and inserts for a few years. He developed an array of colors and added metal spark trails to some of his Go Getter shells. John and his long-suffering wife, Karin, drove all the way up from Florida to my place in Virginia for my Fourth of July party the year the Go Getter article below was written. The Go Getter shells he brought were THE hit of the party. I still hear people talking about them. He no longer manufactures his spectacular Go Getter shells, but you can definitely do it yourself.
John's main contribution to the refinement of the Go Getter effect was his adoption of atomized aluminum in place of the magnesium Go Getter formulas originally prescribed by Fish and Johnson. Utilizing aluminum increased manufacturing safety and reduced costs. John's technique of using ball shells, different from traditional canister shell techniques, works very well and is much faster. You can use either plastic or paper shells. (See my notes at the end of the article for a bit more information on shell construction and fusing.) He also greatly enhanced the range of Go Getter colors and spark trails. Go Getters of all colors are now frequently seen in imported shells from China and Europe, just another example of the R&D contributions of American amateur fireworks makers to the craft of fireworks. Thank you, John, for all the work you did in furthering the development of Go Getters and for so generously sharing your work with us.
The Go Getter article below has been modified by me only slightly by removing the table of contents.
-- Harry Gilliam
Ammonium Perchlorate/Aluminum Go Getters
By: John W. Driver
WARNING: THIS PAPER CONTAINS DESCRIPTIONS OF PROCEDURES WHICH SHOULD ONLY BE ATTEMPTED BY PERSONS POSSESSING AN ADEQUATE UNDERSTANDING OF THE CHEMICAL AND PYROTECHNIC PROCESSES INVOLVED AND WORKING AT AN ADEQUATELY EQUIPPED, LICENSED LOCATION USING ALL APPLICABLE SAFETY PRECAUTIONS.
©Copyright 1997 John W. Driver All Rights Reserved. No portion of this document may be reproduced without the written permission of the author.
Introduction and Original Formula
It all started several years ago when I watched a video of a PGI Convention. I observed a new-to-me effect; it looked like the stars were "swimming." After cleaning my glasses and viewing it again, sure enough, self-propelled stars. I already had Troy Fish's article entitled "Green and Other Colored Flame Metal Fuel Compositions Using Parlon" published in Pyrotechnica VII but didn't make the connection. It all became crystal clear after obtaining a copy of Dave Johnson's book, "Go Getters." Well, for one reason or another, the idea somehow got shuffled to the dark reaches of my mind. Although it did resurface from time to time, the final catalyst didn't come until the 1994 convention in Pennsylvania. I witnessed some Go Getter shells in the opening display by the CPA and particularly liked the blue ones. Next came the Go Getter seminar by Dave Johnson and Mark Raitzer, which explained how to make the little critters. Unfortunately, the seminar only presented the same three colors that had been listed in Johnson's book, namely red, green and yellow. All utilized magnesium as the metal fuel. Since I really like the color blue, the hunt was on. Inquires of several fellow pyros resulted in no answers for blue Go Getters. The puzzle finally started to fall into place following a perusal of Joel Baechle's "Pyrocolor Harmony." Right there on page 34 was an ammonium perchlorate formula for violet with an interesting footnote stating "The violet with 10% aluminum and no hexamine is an excellent 'go getter' composition." The original violet formula is as follows:
Having neither rosin or vinsol, I substituted saran resin (I figured a little more chlorine donor couldn't hurt). Also, for the atomized aluminum, I used 325 mesh, 30 micron, spherical (KSI now Skylighter #007) aluminum. While this revised formula worked nicely in initial tests, I soon started observing bubbling and foaming in the tubes about one hour after they had been poured. In most of the tubes the fuses disappeared completely, as they sank out of sight to the bottom of the tubes due to the agitation provided by the bubbling. The foaming was probably caused by the formation of acetone acids which reacted with the aluminum. In any case, the Go Getters were useless since most of the fuses had disappeared and I didn't like the looks of them anyway.
In desperation, I tried something that shouldn't have worked quite as well color wise as the oxychloride. By substituting copper carbonate for the copper oxychloride, the foaming stopped and, judging by the comments I received at the PGI convention, the effect was quite well received. The final formula is presented below, along with a formula for orange Go Getters. If you want to shift the color more into the "pumpkin" range, eliminate the ultramarine and increase the calcium carbonate to 15%.
|BLUE & ORANGE ALUMINUM GO GETTERS FORMULA |
All chemicals are run through a mixing screen a few times and, with the aid of a funnel, are poured into an acetone proof plastic (I use an empty mustard squeeze-type bottle made of LDPE (low density polyethylene)). If you do not have access to LDPE containers, you must experiment to find a flexible plastic material that is not affected by acetone. I find that, except for occasionally plugging up, the squeeze-type container works very well and gives more control over the flow of material than pouring from a plastic drink cup. Dave Johnson's book covers the construction of Go Getters in great detail, so I will only point out the highlights and differences.
I use a standard 9/16" ID. x 1 1/2" long spiral-wound, machine-made tube with a 1/16" wall thickness and standard 9/16" end plug. The end plug does not need to be glued in as the parlon, once it sets up, is quite hard and will not blow the plug until the Go Getter is almost done burning, if at all. The tubes are then bundled into a convenient size package (I use bundles of nineteen) with rubber bands and set on plastic film (Saran Wrap), ready for filling. While Go Getters made with these tubes go quite nicely, the tubes are still relatively heavy. If you have the inclination, you might want to try hand-rolling some tubes from Kraft paper with a thinner wall to see if they fly better. Go Getters are end burners, so you should not have to worry about blowing out the tube.
A 90:10 mixture of dry acetone:xylene is used as the solvent. Both acetone and xylene are hygroscopic (absorb water) so it is important to use dry material. Fresh solvent is best, but if you have any doubts about the dryness, the mix may be dried in the following manner. First, the desired quantity of solvent mix is prepared. Then a small quantity (an ounce or so) of drying agent (I use calcium chloride or "Damp RidTM" in Florida) is placed in an acetone proof plastic container (plastic two liter soda bottle), the solvent is added, the container is capped and shaken to allow the drying agent to absorb the water. CAUTION: be sure to release the pressure in the container by loosening the cap/lid from time to time. Only a brief time is needed to absorb the water and then the mix is allowed to settle for a few minutes. Lastly, the mix is filtered to remove any solids by pouring it through a double layer of coffee filters and stored in an air/moisture proof plastic container and the drying agent is discarded (it's cheap). It is a good idea to dry only as much acetone as is needed for the batch of Go Getters you are making.
CAUTION: acetone evaporates very quickly, the vapors are heavier than air and extremely flammable. Good ventilation and no sparks are a must.
The acetone/xylene solvent mix is added to the composition in the squeeze bottle at the rate of 35-45% by weight. Some experimentation may be necessary to get the proper viscosity of the mix with your chemicals. The correct consistency is somewhere around a slightly thickened pancake batter (depends on your recipe). After placing the top on the squeeze bottle, squeeze out about 25% of the air (to allow for expansion of the acetone vapor), hold your gloved finger over the spout and shake vigorously for two to three minutes or until everything is thoroughly blended. Depending on the size of the batch you are pouring, you might want to give the bottle a good shaking every once in a while just to keep everything in suspension (don't forget to squeeze some air out first). The tubes are then filled to the brim, ready for insertion of the fuse. It is a good idea to keep a toothpick handy to unplug the nozzle and some paper towels to wipe the nozzle and your hands.
The Fuse (The Secret)
Black match or any other potassium nitrate containing fuse probably should not be able to be used with aluminum Go Getters like it can with the magnesium varieties. This is because of the ammonium perchlorate and potassium nitrate reacting to form the very hygroscopic ammonium nitrate, which may result in a wet interface between the fuse and composition. The trick is to use Thermolite. The Thermolite will not react with the composition and provides a nice hot flame to light the Go Getters. Cut (carefully) the Thermolite in about 1 ¼ inch pieces, remove as much of the fabric-wound outer layer as you can, bend the fuse into a narrow "U" shape and insert it into the Go Getters, "U" end first, about half way, and lay them over against the side of the tube. Make sure you prepare enough fuses to complete the job before you mix the slurry. Once you pour the Go Getters, the stuff sets up rather quickly. After the fuse is inserted, set them aside to dry on a piece of plastic wrap until no odor of acetone is detected (about 3-4 days). As the Go Getters dry, they will shrink back into the tube a little because 1/3 of the slurry, by weight, evaporates.
By having two ends of the fuse exposed to the expanding flame front within the shell, ignition of the Go Getters is improved and more initial thrust is generated due to the two points of ignition.
Construction of a Six-Inch Round Go Getter Shell
A round Go Getter shell is constructed much like any other ball shell of comparable size with a few minor differences. The time fuse is cut to allow a delay of about 4 seconds between cross matching. A fuse extender made from three turns of 30 Lb. Kraft paper is rolled on a suitable former and only pasted on the last 1/4" or so of the trailing edge, just enough to keep the tube from un-rolling. The tube is then slipped over the cross-matched end of the time fuse and securely taped in place (remember, at this time you only cross-match the end of the fuse that goes inside the shell). The fuse is glued into the hemisphere and the fuse extender is cut off so that it just reaches the center of the shell. Two or three pieces of thin black match are inserted into the extender tube to quickly transfer fire from the cross match to the center of the shell (just like building a regular chrysanthemum shell).
There are two theories behind the burst charge for Go Getter shells. The first is to use a relatively hard burst to scatter the stars and let them swim back toward each other. Since the stars are placed randomly in the shell, and they are not smart enough to know which way to go, the result is a big boom and Go Getters scattered all over the sky, with the distinct possibility that some of them will be driven toward the ground hard enough that they will not burn out before impacting the earth. My preference is to use a soft break, only strong enough to open the shell and light all of the stars. Meal powder on rice hulls works well for this purpose. A 3:1 or 3.5:1 ratio of meal to hulls works very well. Remember, they are self-propelled stars and don't need to be blown all over the place with your favorite "atomic" flash burst.
Putting It All Together
Two pieces of tissue paper are cut of sufficient size to line the shell hemispheres with enough left over to fold across the top of each shell half to hold the contents in the halves while assembling the shell. A hole is pierced in the center of one piece of tissue and the tissue is inserted over the time fuse and smoothed out against the inner wall of the hemisphere. The second piece of tissue is placed in the other half in a similar manner except for the hole for the time fuse. The Go Getters are then placed against the inner wall of the shell about half way up the wall. Care must be exercised not to obscure any of the fuses. Burst is now poured in to fill all of the crevices between the Go Getters. At this point, just enough burst is used to fill the crevices and leave a thin layer over the already placed stars. Stars and burst are added in alternating layers until the hemisphere is full. Remember to keep forcing burst into the crevices between the Go Getters as this is the only way to ensure shell integrity. The extra tissue that has been hanging over the edge of the shell and getting in the way is now folded toward the center of the shell, secured with a couple of pieces of masking tape. The other shell half is finished in the same manner and the two halves are joined using your favorite shell glue.
As was discussed earlier, you do not need a hard break for Go Getter shells. Consequently, you do not need to paste endless layers of paper on the shells. Four to six layers of 60 lb. Kraft paper will suffice. After pasting, the shell is finished in the normal manner with the final cross match, lift and leader. Good luck and SAFE SHOOTING!
MORE ON COLORED GO GETTERS
Subsequent to writing the original article, I have done some additional experimentation as explained below.
Colors and Catalysts
I didn't realize when I first started making the blue Go Getters that copper acted as a catalyst to increase the burning speed of the composition to make a more lively star. It is therefore quite easy to shift the color toward either purple or lavender by substituting the proper amount of strontium carbonate for some of the copper carbonate to achieve the desired color.
Other colors require a different approach since copper compounds are out of the question due to the blue tint imparted by them. The answer to this quandary may be found with the High Power Rocketry people. More specifically, an article in the Journal of Pyrotechnics # 3 entitled "Ammonium Perchlorate Composite Basics" which discusses, among other things, burn rate modifiers which may be used to control the burning speed of ammonium perchlorate propellants (remember, these Go Getters are baby rockets). Due to time constraints, little research has been done by this author on the suitability of these catalysts, but red iron oxide seems like a likely candidate.
While Thermolite makes an excellent fuse for Go Getters, its limited availability and high cost discourage its use in any but the smallest of projects. The most promising solution is to use an alternate form of fuse. My first thought was to use an H-3 based fuse (potassium chlorate and air float charcoal), but this is not a viable alternative due to the double decomposition reaction between ammonium perchlorate and potassium chlorate resulting in the formation of the rather sensitive ammonium chlorate (Lin Collins, private communication, September 1995). The next logical choice would then be match based on KP burst (75% potassium perchlorate, 15% air float charcoal and 10% sulfur with 5% additional dextrin). Because the perchlorate isn't particularly soluble in water, you end up with a slurry which must be stirred from time to time while the match is being made. Five strands of single ply cotton string works well for this purpose (you want a fairly small diameter match, like the black match used for cross matching). The slurry must be thoroughly worked into the string before it is drawn through the sizing orifice. When the KP match is dry, cut it into lengths of approximately 1 1/4" or so and insert them about halfway into the filled tubes as you would with Thermolite.
The final step is to prime the fuses to insure complete ignition. For this purpose, the Go Getter (fuse end down) is dipped in a N/C lacquer solution and then dusted with meal powder (home made meal is entirely adequate). Since no moisture is involved, there is no worry of the ammonium perchlorate/potassium nitrate double decomposition reaction occurring.
Johnson, D. S. 1989. Go Getters.
Fish, T. 1981. Green and Other Colored Flame Metal Fuel Compositions using Parlon.
Issue VII, Pyrotechnica: Occasional Papers in Pyrotechnics, Austin, Texas.
Sobczak, R.R. 1996. Ammonium Perchlorate Composite Basics. Issue no. 3, Journal
of Pyrotechnics, Whitewater, Colorado.
Baechle, J. H. 1989. Pyrocolor Harmony, A Designers Guide.
Notes from Harry Gilliam:
- The ammonium perchlorate is the 200 micron variety
- The uncoated atomized aluminum should be -325 mesh, average particle size 12-32 micron.
- Thermolite is hard to get but worth it if you can lay your hands on it. The last place I saw it for sale was from Coonie Coyle: Coonie's Explosives & Powder, 512 East Lea Street, Hobbs, NM 88240, (505) 393-0166
- Mix and dry the solvents EXACTLY as John has recommended. Do not skip the drying step. If you have any doubt that your solvents may have water in them, dry them before using. Removing the water from this composition is necessary for your safety. The presence of water in this composition could cause the mixture to heat up and spontaneously ignite. Removing the water will also help the Go Getters to dry more quickly.
- I suspect you can substitute one of our flying fish fuses for a ready-made fuse, if you do not have Thermolite or don't want to make KP fuse. Try silver or crackling flying fish. I have not tried this, so consider it experimental.
- For a time, John was using plastic ball shells, pasted with several layers of paper. My guess is that you can use plastic shells, glued well, and then add 2-3 "X's" of fiberglass reinforced strapping tape across the equator of each shell. These shells do not have to break hard. So the extra compression added by the layers of paper may not be absolutely necessary.
- Acetone is both flammable and poisonous. Either use it outdoors or in a very well ventilated area. The acetone in your Go Getter goo will dry out quickly while you're squirting the stars. Keep some more solvent on hand to add to the mix so that you can thin it as need.
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