WARNING AND DISCLAIMER: If you are underage, then consult with your parents or guardians before attempting any of this. You are on your own - I'm not responsible for your actions or harm you may bring to others because of your actions. Making the items described below can result in injury or death to you or people in your vicinity. Some things mentioned here may be illegal to make in your city, county, state, or country so check the laws that apply to you before you attempt anything described here. These notes are not complete on purpose. If you are reading them and new to pyrotechnics, then you are making a mistake. Stop now - this page is not for you. Get a beginning book on fireworks (see Skylighter or American Fireworks News (very quick shipping) for a start) and read up. You can't make any of this work without more information so read up or join a club or ask someone to help you.
Making a Small Shell for a Cake or Small Mortar
You would think that a small shell for a cake, insert for a larger shell, or a small mortar would be easy. As many have found out, it can be quite difficult making a good small shell. Here is a fool proof way of making one type of shell that can deliver about any kind of small payload - it is 3/8" in diameter but it packs a nice punch and it never fails to light. It is quick to make so you can roll up a few dozen without feeling like you spent too much time on the bench.
This process, once the case is made, is similar to making a double voice cracker (see: http://www.wichitabuggywhip.com/fireworks/doublevoice.html)
Measure out a few inches of gummed paper
Wet just the last few inches (I mist it with my spray bottle) and roll on a 3/8" rod
Finish the roll and cut the tube in half. If it tends to unroll, then tape it with clear tape.
Put tube over a 3/8" or 1/2" aluminum plug with a hole in it
Be sure there is a fuse in the hole!
Load with about 3/8" clay
Tamp lightly - the tamping rod has a hole in the end to accept the fuse.
Fill shallow end with damp star comp, tamp with rod used in previous picture, dry, prime fuse (not primed here).
Fill other end with garnish. Dragon's eggs and flash are popular but flying fish or falling leaves would also be great. Close other end with paper plug - hot glue and spike if using flash - or tape with masking tape if softer break is needed. These were flash filled and spiked with stranded tape
To this point, we have a cardboard tube with a clay center bulkhead. A fuse runs through the bulkhead connecting the two sides. One end of the cardboard tube has the primed fuse protruding out. This is filled with compacted star composition that is wetted. The other end is closed and holds flash, dragon's eggs, flying fish, or other garnish. Dry this device for a few days in a drying oven or warm/dry place.
Click on the above image and see the short movie. This is a mix of comets and color-to-report 3/8" mortar shells coming from a 36 shot cake.