In the next few weeks we will show you some ways to plan and set up a consumer fireworks display, including tips on firing portions of the show electrically. We’ll discuss electric firing systems and electric matches.
Why would one want to fire some or all of a fireworks display electrically? First, it’s safer to fire a device electrically than it is to light it by hand, especially if the item is in the middle of a field full of similar fireworks. Electric firing also enables the display operator to sit back and enjoy the show along with the rest of the crowd. Precision timing is also enhanced by shooting with a firing system.
Many of us are familiar with small firing panels and electric matches from our early days of experimenting with model rockets, since small versions of the igniters are used to remotely fire those motors.
Quite a long time ago I made some electric matches using a kit which instructed me to just dip the bare ends of some wire into a composition that was dampened with some acetone, and then again into a finish coating.
I didn’t have much luck with that system, and ended up firing the electric matches with a high-voltage system just to get them to ignite. I was disappointed. Ever since then I’ve had access to commercially made electric igniters, since I am an ATF licensed display operator.
But, you may not have access to commercial electric matches: They are a regulated explosive and require an ATF license to purchase them. But making them yourself is legal and does not require an ATF license.
Now and then my curiosity has been piqued when I’ve seen some of the various methods for making electric matches. I’ve seen the match heads that you solder wires onto, and then dip into various compositions. Also, there are ematch blanks, which have wires already soldered onto match heads, ready for the application of the pyrogens (combustible compositions).
So, I figured that the only way I could credibly discuss these homemade electric matches was to play a bit with them myself. Fortunately, I just recently spent some time in Virginia at the Skylighter facility, and was able to pick the brain of Brian Paonessa, who is one of the main Skylighter pyro experts, and who has experimented extensively with homemade electric igniters.
I assembled a kit of materials to bring home and play with.
The electric matches I’ll be discussing have five basic parts:
Insulated, two-conductor, wire “leads” connected to the match head. The insulation is stripped back for about an inch at the opposite ends of the wires from the match head. These bare wire-ends are twisted together (shunted) to prevent a current from passing from one end of the wire, through the match head, and out the other end, accidentally firing the electric match.
The match head consists of a small chip of circuit board, which has a metallic conducting surface on both sides, separated by an insulating material.
An extremely thin (48-51 gauge) strand of nickel-chromium (nichrome) bridge wire is soldered to the chip, with one end soldered to each side, and with the exposed wire spanning the end of the chip and crossing over the insulated core.
Pyrogen: The tip of the chip, containing the nichrome wire, is dipped in pyrotechnic composition, in one or more coats, and then into a hard, smooth finish layer.
Finally, a plastic, protective-shroud covers the match head to prevent accidental ignition of the sensitive pyrogen as a result of friction or mechanical shock.
When enough current is passed through the ematch leads, the nichrome wire heats up and ignites the pyrogen, producing a flame, which will ignite the flammable materials that the ematch is in contact with. This happens in milliseconds. When it does, the nichrome wire burns through and is consumed, breaking the electric circuit.
Note: If one can obtain circuit board blanks with conductive coating on both sides, Skylighter sells the thin nichrome wire so that heads can be cut to size and the nichrome soldered onto them. This is a very painstaking process. In the back of my mind, a future project would be to buy some copper-foil-tape from a stained-glass supply store, press the foil tape to both sides of a piece of cereal-box cardboard, and cut match heads out of it. Soldering the nichrome wire onto those heads would produce homemade match heads.
If you go to the Skylighter (http://www.Skylighter.com)
website, click on the Ignition Supplies
under the Order Products heading, and scroll down to item number GN5030, Electric Match Heads, you can “click here” to see the instructions for this item. They detail the soldering of the wires onto the match heads, and then the coating of the match head with the various layers of homemade pyrogens.
At this stage, I like to work with short lengths of wire, so I cut about a foot of shooting wire, strip an inch of insulation from the wires at one end and lightly twist them together to shunt them, and strip about a quarter inch of insulation from the wires at the other end.
Soldering the wires onto the match head is easier if you “tin” the wires by coating them lightly with solder first. Then, the tinned ends are pushed together until they are just barely separated, and the match head is slid between the wires and gently soldered in place per the instructions.
A small “pencil” soldering iron and rosin-core solder come in handy for this process. You want to be careful to avoid overheating the match head during the soldering.
Note: The ematch heads do not come with plastic protective shrouds, which many of us consider to be an essential safety component of ematches. Rubber surgical tubing, of the appropriate inner diameter, can be cut to 1″ lengths to use as protective shrouds on finished electric matches.
Whether I’ve purchased the pre-soldered ematch blanks, or have made them by soldering wires onto the match heads, I like to test the blank at this point. I do that two ways. I use Skylighter’s Ematch Tester
(GN5005) and make sure it lights up when the untwisted leads of the ematch are pressed to the sides of the tester.
I also use a Radio Shack Digital Multimeter to check the resistance of the match. All of the matches I’ve been working with have a resistance of 1.1 to 1.2 ohms. If the reading is significantly different, I discard the ematch blank.
This testing insures that the nichrome bridge wire is in place correctly, and is intact. It also proves that there is no excess solder bridging the two conductive surfaces on the chip, or between the wires.
Note: It is important to use a digital meter to check electric matches. Test it on a finished electric match first in a safe location. It has to have been proven to use a small enough amount of current that it will not fire ematches. My understanding is that the test current in analog meters with needle-readouts will accidentally fire ematches if that type of meter is used to test them.
Now, with the tested ematch blanks, we have assemblies that are ready to have their ends coated with pyrotechnic compositions.
I am going to try some different ways of doing this.
The above cited match-head instructions offer specific directions for coating the tip of the match head with three different homemade compositions: a primer comp, an ignition comp, and a final protective coating.
Or, Skylighter sells the GN5050 Electric Match Dip Kit, which comes with all the necessary chemicals, materials and tools, and instructions (which may be seen by following the above cited links and scrolling down to the GN5050 Dip Kit listing and clicking on “click here for instructions on making electric matches“).
These instructions include very complete safety precautions, which I am not going to repeat here, but which are necessary to understand before proceeding with the following steps.
The first thing I did was to remove the plastic shrouds from the match heads on the pre-soldered blanks.
I used the Skylighter Dip Kit to coat some match blanks, per the instructions in the kit. I found that I had to add quite a bit of the thinner to the mixed first-coat pyrogen to get it thin enough to coat like the directions specify. Use a thin coat, which drips off one drop after dipping the match head into the pyrogen about 3/16″.
I hung the bent matches on a piece of shooting wire strung between two wood posts and allowed them to dry for a couple of hours.
I decided to coat a dozen of the blanks and then apply the finish coat, and then test fire them to make sure the system I’m using is working.
This dip kit will coat hundreds of ematch blanks, so it’s a good idea to prepare all the blanks you want to coat before starting the coating process. Once the pyrogen is mixed, it is uncertain how long a shelf life it has, and you have an explosive slowly setting up in a glass bottle. I recommend mixing it, using it relatively quickly, thinning any excess with more thinner, then pouring it on some newspaper and burning it.
As you are working with the wet pyrogen, don’t allow any dry “crusties” to form on the edge of the bottle top. Push them back with your finger and stir them into the wet mix.
Brian says that the most common sources of failures when using this dip kit are applying the pyrogen too thickly or too far up the match head. Make sure the mix is thinned as per the instructions, and that the heads are only dipped about one third of the way, or about 3/16″. It’s also very important to thoroughly mix the components, and then mix them a bit more. Under-mixing the ingredients is another common cause of ematch failure.
The right consistency will cause one small drip off the end of the match once it is removed from the pyrogen, and a nice, smooth, slightly rounded match head will form.
Once these matches were dry, I coated them about half way up the head, just past the first layer, with the red lacquer finish coating, per the directions.
I wanted to try the dip-coating method described in the instructions for making ematches using Skylighter’s match heads. This process details the mixing of two homemade pyrogen coatings, and then the final application of a nitrocellulose lacquer
Note: This process uses two sensitive compositions–Dark Flash and H3. The directions must be followed precisely to avoid accidents. These compositions are mixed in a wet state. I can’t emphasize enough that these comps become very powerful and sensitive when they dry out. They must be worked with while they are wet. Any excess should be thinned and disposed of while it is still wet.
The “primer” coat is 50/50 potassium chlorate/antimony sulfide. Five grams of the potassium chlorate is screened through a 100-mesh screen. It is then mixed with 5% NC lacquer until a syrup is formed. Next 5 grams of the -325 mesh, dark-pyro antimony sulfide is mixed in. More lacquer can be added to thin the mix until it can be used as in the directions for the dip kit cited above.
Note: Skylighter sells nitrocellulose (NC) lacquer, which is a 25% solution of nitrocellulose in solvent. To make a 5% solution, weigh out some of the 25% lacquer into an empty, clean, one-quart paint can (from Home Depot or similar), filling it about one-eighth full. Then add four times as much acetone (by weight) into the can, close it, and shake to mix thoroughly.
Mixing this comp in an HDPE photo-film canister using a Popsicle or coffee-mixing stick (free at every 7-11), works well. I then dipped some ematch blanks into this comp and allowed them to dry completely.
This primer coating was then coated with the H3 composition. 7.5 grams of potassium chlorate was dampened, as above, with 5% NC lacquer. Then 2.5 grams of airfloat charcoal was added to that mix and stirred thoroughly. Then more lacquer was added until the thin syrup consistency was achieved.
Then the ematches were dipped into this second-coat composition and allowed to dry once again.
Finally I dipped the dry match heads into 5% NC lacquer, completely coating all the pyrogen layers, up about half way on the match heads to create a protective final paint job on each match. Once again, the matches were allowed to dry completely (anywhere from a couple of hours if it is warm to overnight).
I’ve recently heard about a fellow pyro using regular PVC plumbing cement rather than nitrocellulose lacquer to dampen compositions. I decided to repeat the above process using the PVC cement instead of the NC lacquer.
Using this cement produced easy-to-use compositions, and nice, hard, shiny, black match-heads when they were dry.
All three production methods produced nice, very hard, durable ematch heads.
I wanted to see how much electric current it takes to fire these 3 types of homemade electric matches, and also to see how effective they are at igniting a quickmatch fuse. I installed the plastic safety shrouds on all the matches.
Using a little testing apparatus, I determined that the matches will begin to fire once 0.5 – 0.7 amps of electrical current is passed through them. This specification is similar to commercial electric matches and a good rule of thumb out in the field is to maintain at least one amp of firing current in these firing circuits.
Note: The above info yields a simple rule of thumb out in the field when setting up the wiring for fireworks cues. Using a Skylighter 12 cue wireless firing system, which puts out about 4.5 volts with each cue, you’d want to use one ematch and a maximum of 100 feet of the double-stranded, yellow, copper shooting wire
between the panel and the ematch, or a max of 50 feet of the new orange aluminum shooting wire. If you use a 12-volt firing system, maximum length of these “scab” wires would be 300 feet and 180 feet respectively for use with a single elecytiv match. Using a Skylighter GN6010 Electric Firing Box, which generates 300 volts, you can use a virtually unlimited length of firing cable.
I fired each type of electric match several times. The ematches made with the dip kit really pop and throw out a fast flame, similar to commercial electric matches. The ematches made with NC lacquer and homemade pyrogens burn a little less violently and a bit longer and throw out quite a few orange sparks. The similar ematches, made with the PVC cement, burned nicely, and even a bit longer, throwing out a nice flame for about a half second, like a regular safety match would.
I figured that any of these matches would effectively ignite quickmatch if they were installed in contact with the internal blackmatch. I wanted to experiment with one additional step, which would really throw out a lot of flame and would reliably ignite the visco safety fuse on any cake or device out in the field.
I cut 1″ lengths of the super-fast-fuse, which is similar to quickmatch, but which can be shipped. I then used 2″ long pieces of one-inch wide masking tape to secure the fast-fuse into the ends of the ematch plastic shrouds. Then, with some of them, I installed a piece of visco fuse with the freshly-cut end in contact with the end of the fast-fuse, and secured with another length of masking tape.
All the different types of electric matches performed flawlessly and ignited the visco fuse easily. I was very pleased with their performance and with the opportunity to learn more about how reliable electric matches can be homemade for one’s own personal use.
In the future we’ll be detailing the use of these ematches, and how to wire them up with firing systems for reliable ignition, how to plan a consumer fireworks display, and how to make small mortar racks and set the show up for a night’s festivities.
Stay tuned and stay green,