The people who make fireworks are really clever. They combine a knowledge of chemistry and physics with artistic ingenuity to produce an infinite variety of fireworks bursts. How do they do it? They change the size, shape, density, composition and placement of the stars within the fireworks shell. By doing this they change the shape, speed, direction, burn rate and color of the aerial burst.
B) The outer part of a star ignites first and the inner part burns last. Stars that change colors as they fly have an outer layer that contains one metal salt and an inner core that contains another metal salt.
C) Changing the size and shape of the stars will produce bursts of different sizes, shapes and speeds.
D) Careful placement of the stars will change the shape of the burst. Rounds, rings, palms, willows, chrysanthemums and other burst shapes can be produced. An infinite number of bursts can be produced by carefully varying the shape, size, density, and composition of the stars.
They can also put shells within shells for multiple explosions and bursts. Or, they can include firecrackers, whistles or other noisemakers. Ingenious people can build fireworks shells for an infinite number of visual effects.