Petal

From PyroGuide

A petal is the name for a carefully arranged burst of stars, usually a ball of produced from an aerial shell. While most shells have only a single petal some shells have two petals or more and are called double petal, triple petal and so on depending on the total number of petals in the shell. Petals are not to be confused with pistils.

It is widely believed that double petal shells cannot be made smaller than six inch (150mm) though this is not true and skilled shell builders can and have built double petaled shells smaller than that. Double petal shells are built in a variety of ways, each with an outer petal arranged in a normal fashion, and the inner petal stars arranged like a petal from a smaller shell, typically half the size in diameter. Either the material holding the inner petal together must be of a nature that does not obstruct the spread of fire in the shell, such as tissue, or it should have many holes punched through it to allow the fiery gasses to ignite the outer petal. Burst is placed inside the inner petal, and between the petals and it is common practice to use a stronger burst inside the inner petals. For shells with more than two petals, the process it similar.