Fireworks that are launched into the air typically are fired out of mortar tubes, many tubes that come with consumer fireworks are not reusable or are made out of flimsy cardboard. This is why many pyrotechnic enthusiasts like to make their own mortar tubes.
High Density Polyethylene (HDPE) is the safest materials you can choose when making your own mortars for firework shells. While the HDPE tubing itself offers durability through the ability to withstand higher levels of shock and heat, there are safety and performance measures that you need to take when making the mortar. Namely, this step is plugging the bottom of the tube to prevent gases creating during the lift charge from escaping out.
If lift charge gases leak out from the tube during the igniting, your shell will either “flowerpot” and explode in the mortar or not reach full accent before bursting. When using the recommended size HDPE tube (1 7/8″ interior diameter), the plug in the bottom should be made from approximately 1″ thick wood cut to fit the shape. Pre-made plugs are available from some firework supply outlets. However, making you own mortar tube plugs is easy and takes just a small amount of time.
Supplies needed to make HDPE plugs include scraps of wood around 1″ thick, a hole saw with 1 7/8″ diameter, hand-held drill or drill press, and glue. Before you start drilling, stick the drill bit into the tube, just to make sure your finished product is going to fit the tube. Practice makes perfect, so you may have to repeat the drilling process a few times until you get a good plug. After you’ve got the hang of it, you can knock out a bunch of these plugs very quickly – then you’ll have to pop the plugs out of the wood with a screwdriver.
The next step is to push the plugs snuggly down into the tube, making sure there is no loose space around the edges. Use glue to create an air-tight seal between the wood and plastic as well as the pilot hole left in the middle of your plug during the drilling process. However, applying the glue is mainly for air-tightness, not to keep the wood in perfect place. You’ll also need to send a screw or staple-gun staples into the plug from the outside for maximum security; this should be done before the glue completely dries.
Let your newly plugged mortar tubes dry overnight and then you’ll be ready to shoot off plenty of awesome aerial effects at your next pyrotechnic show! Launching fireworks from your mortar tube will be a blast, you’ll feel like a real pro!