can_shells

Canister shells are becoming rarely seen in the USA. They have been almost entirely overrun by Chinese ball shells in public displays due to price. Canister shells have gained their greatest fame from the island of Malta, where multibreak canister shells, sometimes weighing more than 100 lbs have been perfected. The burst of a canister shell differs from that of a ball shell by breaking in a donut shaped ring rather than a sphere. Often times these shells are filled with smaller shells that break in a series of rings after the initial burst.

The simplest of canister shells will be described here. Lower on the page is also a video related to multibreak shells and how they are made.

The drawing to the right shows a single break canister shell loaded with stars as the only effect. Some terms and processes described assume the reader has also read the aerial shell page.

The most obvious design change from a ball shell (other than shape) is that a canister shell uses a fuse inserted into the top of the shell rather than the bottom. A piece of quickmatch (1) passes by the top fuse assembly (3) and ignites it on its way to the black powder lift (2). The quickmatch that spans the space between (3) and (2) is called a passfire. This is done because the place the fuse (4) passes into the shell is the weakest spot. It therefore needs to be on top of the shell to avoid the high pressure created by the lift (2).

At (3), a slit is cut into the quickmatch pipe and the black match inside is pulled out just enough to tie it to the top of the primary fuse. This fuse is called a spolette (4), and consists of a hard paper tube with a solid core of black powder rammed into it. The length of the core determines the amount of time it will take for the spolette to burn through. An inch of black powder may burn at 2 seconds for example, and an inch and a half may burn for 3 seconds. In addition to having the black match from the quickmatch tied to it, the top of the spolette also has several pieces of loose black match tied over the top to aid in ignition.

In a similar way to a ball shell, a passfire is made to make the point of ignition inside of the shell directly in the center (5). This passfire is made by inserting strands of black match into the part of the spolette tube (4) that has not been completely filled with black powder. Another thin tube made of only one or two layers of paper is rolled over the end of the spolette and tied around the black match.

Once the quickmatch (1) has ignited both the spolette (4) and then the lift (2), the pressure from the lift fires the shell from the mortar into the air. Once the spolette burns to the end and ignites the passfire (5), the break (6) is ignited. In canister shells, it is somewhat common for the break to be nothing but granulated black powder. As in ball shells, black powder coated onto rice hulls may also be used on occasion. The break both ignites the effects (7) and bursts the shell.

The innermost wall of a canister shell (8) is made of heavy brown paper or thin cardboard. Once the shell has been filled with effects and burst, string is wrapped tightly around this layer. To the top and bottom of the shell is added a heavy cardboard disc (10), which both helps seal the shell closed and offer protection from the lift (2). The discs are held on by the string as can be seen in the photo to the right. The process of tightly wrapping a shell with string as is shown is called spiking.