How do fireworks produce their colors
Chemicals that give off bright, distinct colors when burned provide the
spectacular colors associated with fireworks. Charcoal and iron, for instance,
burn brilliant orange. Strontium salts produce red and barium nitrate gives off
green. Blue is the most difficult color to produce, and chemists are still
searching for a compound that produces a true shade of blue.
Once a manufacturer chooses the colors for a firework, the appropriate
chemical powders are compressed into small pellets called stars. These stars are
normally packed into a Shell containing gun powder. The shell is then put in a
launcher — a close-fitting tube, closed at one end, that has been hammered into
the ground. The tube acts like a cannon as the pressure from the exploding
gunpowder and expanding gases become trapped behind the shell arid shoot it into
the sky. Depending on the shell design and amount of stars, the
firework display varies. A Roman candle, for example, contains only a few stars
and shoots them out one at a time, while an aerial shell contains hundreds of
stars — each of which leaves a single trail of brilliant color in the sky. For
more information about fireworks, contact the National Council on Fireworks
Safety, in Washington, D.C., at www. fireworksafety. Com.
A．shells that are put in a launcher B．heavenly bodies in the sky C．brilliant colors produced by fireworks D．compressed chemical powder