The Match-head Mortar

All text and images © Copyright July 2007 by Travis J. Lyon

The Match-head Mortar is a pyrotechnic device that is quite simple to make out of ordinary household products. It's fun to do, does not cost much, and is, for the most part, safe to construct and ignite. Here are the items you'll need:
Step One:
Unwrap one tampon and take out the cotton. It is important to use the cardboard tampons for this project, because they are less dangerous than plastic in the event something were to explode (unlikely but not impossible) and the burning fumes of the cardboard will be less of a respiratory hazard. Separate the two cardboard tubes.
Step Two:
Use the hobby knife to slice off the ridged end of the larger diameter tube. This is done gently and with shallow cuts, slowly working around the cylinder so as not to press it in and deform it. This will be the main mortar tube, so the object is to make it as long as possible. A box of 20 or so generic tampons can be purchased at a discount store for about $3.
Step Three:
Cut a 1" square out of the index card and glue the large tube flush with the surface. When doing this, it may be best to glue the uncut end of the tube to the surface, as this end of the tube is perfectly flush from the manufacturers cutting and will provide a better seal. Merely put a thin layer of glue around the thin edge of the tube for quick drying... in other words, don't overdo it. A little glue will be all you need. Now set this piece to the side for a moment.
Step Four
I prefer to make a sturdy base for the mortar, so cut another 1" square out of the corrugated ardboard, then glue it to the mortar tube and thin base. Take a quarter or two and set it on top of the upright assembly to press it and keep it together while it dries some more. Set it to the side.

While that is drying, it's time to make the ignition or lift charge.
Step Five:
With the smaller diameter tube, slice about 1/4" to 3/8" off the smoothest end. Next, tape up one end of this small slice of tube with the scotch tape. Note that this piece will be fitting into the main part of the mortar tube, and it is already a snug fit, so try to minimize the amount of tape folded over the sides of the tube. This piece of tape is only the top of the ignition charge, so it does not need to be particularly sturdy... just enough for the next step, adding and containing the fuel.
Step Six:
Your fuel will simply be the match heads. You can use the scissors to cut all the matches out of the matchbook, to save you some 'tearing' time. Then, with either the scissors or the hobby knife, cut of several mastheads. Do your best to cut the heads off, leaving as little of the cardboard matchstick as possible. Use caution to as not to inadvertently ignite any of the heads and collect them into a bowl or other tray. The object will be to fill up the ignition charge, so depending on the brand of matches, it should take anywhere between 15 to 25 match heads.
Step Seven:
Put the match heads into the lift charge. Compact them as much as possible by gently tapping the charge on the work surface to settle the individual heads into place. Do not overfill... when finished, the heads should be no higher than the top of the lift charge cylinder, which will be plenty. Now, cut a small piece of tin foil, just big enough to fit over the lift charge. Too much foil and the charge will be difficult to get into the tube. With the tinfoil on, poke some very small holes in it with the hobby knife or a needle. Set this to the side for a moment.
Step Eight:
Back to the mortar tube. Now, you will need to get a fuse in, over which will sit the lift charge. Fuses can be purchased, or, as I prefer to do, recycled from a small bottle rocket you might have lying around. If recycling, be sure to dispose of the rocket's explosive "body" in a safe place away from possible ignition.
Step Nine:
Next, drill a hole wide enough for the fuse to fit into, just at the base of your mortar tube. Try to fit it as flush with the base as possible. You can drill a hole using the hobby knife, spinning it in a tight circle until you push through the mortar tube wall. Optionally, a small but effective, pen-knife sized hand drill can usually be found at a hobby or craft store for $15 to $20, and may come in handy for other household uses as well.
Step Ten:
Insert your fuse into the drilled hole. Once the fuse is in the tube, try to bend the tip around so it forms a sort of a curve in the bottom of the tube. This will help ensure the lift charge ignites once the fuse is lit. lastly, you may wish to run a bead of glue around the base of the outside of the mortar tube, to be sure that everything stays in place, especially if you were sloppy drilling the fuse hole.
Step Eleven:
When the fuse is inserted, now push the lift charge into the mortar tube, foil-side down. It should be a snug fit and pushed down as far as it will go without damaging the rest of the assembly.
Step Twelve:
The lift charge itself is not supposed to go up in the air, though. You need to make another piece of tube, one that will be propelled out the top. Think of this as the "bullet" in the gun barrel or, in consumer fireworks, the part of the display that makes the burst.

Normally, this part of the firework is made from an explosive compound, but the construction of this type of this can also be dangerous. But for the sake of this project, the concept is intact, just without the bang.

Slice another end off the small diameter tube, about 1/8" to 1/4" in length. This piece will need to slide freely in the main mortar tube, so do not put tape or anything else on it's sides. Simply use some of the cotton from the tampon to plug the cylinder. single ply toilet paper or other light material will also work. With conventional fireworks, another timed fuse would be inserted into this, which would ignite when the lift charge explodes. Once the propelled "bullet" canister reached a certain height (determined by this second fuses timing) the composition within the shell would explode, making the signature colored burst. But because we are stuffing it with cotton, the dangers (and, admittedly, beauty) associated with this aerial burst is greatly reduced.
Step Thriteen:
With the projectile assembled, slide this into the mortar tube until it rests on top of the lift charge. You're almost done!
Step Fourteen:
The final step is to be sure there is a solid seal around the open, top end of the mortar tube. This will add compression and extra 'pop' to your launch. There are two ways to do this:

1. Cut a small disk out of the index card, just wide enough to fit into the mortar tube, then push it down overtop of the projectile. This method is more difficult, especially on such a small scale, since the disk will want to slide sideways down the inside of the tube. It is also difficult to cut the disc just right... not to big, and not to small. The tighter the seal the better.

2. The preferred way , and much simpler way is to cut a small square of plastic wrap and affix this over the top of the tube. The seal will be tight, and it requires less precision. Simply smooth the wrap over the top of the tube then tape it into place. Use several small pieces of tape instead of trying to wrap it around the tube. Smaller pieces will allow you to tighten up any slack in the plastic wrap by pulling the wrap down as ou secure the tape in place.
When it is all wrapped up and tight as a drum, that's it! You're finished. Well... almost. You still need to light it! Be sure to do this in a clear area, though, and definitely outdoors. The matches still pose a fire hazard, as they tend to stay lit even after the projectile has been launched... it is a paper mortar, after all, and paper burns easily. The mortar may also have a tendency to tip, spilling these hot embers, and the projectile has some force, so always exercise caution. Other than that, enjoy yourself!

As a final note, there is certainly some room for improvement over this design. A flaming display ot loud report of some sort is desirable, of course, though I've yet to come up with something that does not require the use of professional chemicals and compounds. The goal of the project is to make a quick and easy assembly out of household products, but aside from saturating the projectile's wad of cotton with a flammable liquid, I don't have any terrific ideas yet.

Additionally, the match head lift charge could be improved... the matches are more like a black powder type of lift, not a true explosion. Even more rapid combustion of the lift charge would naturally make the projectile soar to greater heights, but again I've not found a good way to do this without mixing specialized chemicals and powders or using good old gunpowder.

A reusable mortar would be nice, but the ease and cost of doing single shots is not all consuming. with practice and a little preparation, 5 or so single shots could easily be assembled in under an hour. A longer mortar tube could also help optimize the assembly, but the tampons are an ingenious solution, in my honest opinion, without the more complicated construction it would take to make a modified assembly.

But there you have it! Practice on your own and I'm sure you'll find the sky is, literally, the limit.