In pyrotechnics how are tricky shapes like hearts and stars produced?

Question

Are the the colorant pellets pasted on a piece of paper in the desired pattern? Is that paper is put in the middle of the shell with explosive charges above it, and below? What type of charge is used? Is the shell a round one or a cylindrical one? Are colorant pellets round or cylindrical?

Answer 1

"The pattern that an aerial shell paints in the sky depends on the arrangement of star pellets inside the shell. For example, if the pellets are equally spaced in a circle, with black powder inside the circle, you will see an aerial display of smaller star explosions equally spaced in a circle. To create a specific figure in the sky, you create an outline of the figure in star pellets, surround them as a group with a layer of break charge to separate them simultaneously from the rest of the contents of the shell, and place explosive charges inside those pellets to blow them outward into a large figure. Each charge has to be ignited at exactly the right time or the whole thing is spoiled."

Display Firework Types

Planning a Large Firework Display - Information from the DTI

Answer 2

haven't a clue