Persuading Your End Plugs to FitInto Your Tubes

Sometimes when we buy paper end plugs, designed to fit down inside a firework tube, I have noticed that they seem to fit when we buy them, but later they don’t fit so well. If the end plug is too tight, it will kind of buckle when pushed down into the firework tube. Or, if the end plug is too loose, it will just fall down into the firework tube. When an end plug fits just right, it fits snugly into the firework tube. If you hold that firework tube up to a light and look toward the light through the open end of the firework tube, you should see no light around the end plug.

Paper end plugs are made commercially by ramming damp disks of thin cardboard into a hole using a "mandrel". These mandrels and holes are made in various sizes to produce the different size end plugs you buy from us. After they are pressed into shape, they are heat-dried. Subsequent increases and decreases in moisture content of the end plug cause many of the end plug-sizing problems that we encounter. The end plug simply shrinks and enlarges on its own.

If your end plug is too loose in your firework tube, dump the end plugs into a big plastic bag, and lightly (just 2 or 3 spritzes) mist the batch with water. Shake them up, close the bag, and let the end plugs sit overnight. The end plugs will swell and may do so enough to fit your firework tubes.

Conversely, if your end plugs are too tight, drying them can shrink them enough to fit. Just spread your end plugs out on some flat surface and keep air moving over them for a day or so.

Even end plugs that are still too large can be made to fit properly into your firework tubes, if you will press them in using a wood or aluminum rammer whose diameter is just slightly smaller than the firework tube. Place the end plug over the end of the rammer. Then slide the firework tube down over the end plug on the rammer.

With any of the shrinking and expanding methods described above, you can test whether it works on one or two end plugs first.
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