sodium= yellow
barium= green
strontium= red
copper= blue
While the metallic element dictates the color produced, the compound that contains the element has a profound effect on the type of flame.
Calcium does not produce an exciting color by itself, but it enhances colors of other substances. Chlorine does not produce colored flames by itself, but the presence of chlorine greatly enhances the development of color from metallic elements. Chlorine-containing substances such as chlorate or
perchlorate oxidizers or organic chlorine compounds such as polyvinyl chloride or hexachlorobenzene provide chlorine atoms to enhance volatility and light emission. Certain substances are included for specific effects. Iron filings sparkle and flash when mixed with other burning materials; the metallic iron oxidizes to produce Fe 2 O 3 , a process that produces a large amount of energy sufficient to cause the reacting iron particles to glow.
Titanium metal is also used for production of sparks. Zinc is used in some smoke formulas and to produce star effects.
Fireworks consist of a source of energy such as a mixture of a fuel and an oxidizing agent that react to produce high temperatures and some substance that will emit brightly colored light. One of the simplest firework devices is a sparkler. Sparklers typically consist of a metal wire coated with a mixture of fuel and an oxidizer (mixed in proportions to allow burning), iron filings, and a glue to hold the components together. When the sparkler is ignited, the fuel and oxidizer burn, heating the iron filings so that they sparkle. Other substances such as zinc or magnesium alter the character of the sparks.
Firecrackers contain flash powder (a mixture of an oxidizer such as potassium chlorate or perchlorate and powdered aluminum or magnesium) or black
gunpowder in a paper tube. An attached fuse ignites the flammable mixture, which burns explosively, producing gases that rapidly build up pressure and burst the container. Aluminum and magnesium components produce brighter flashes.
Aerial fireworks usually are of two types, aerial shells fired from tubes and the traditional skyrocket. Rockets are made of cardboard tubes filled with a mixture of fuel and oxidizer in proportions that allow continuous burning rather than explosion. Expulsion of gases from the tube propels it skyward. Rockets often contain explosive charges to explode after the propellant charge burns out; the composition of the explosive charge determines the colors produced.
Aerial shells are small balls of explosive material fired from a steel or cardboard tube or stand. A lifting charge throws the ball skyward, and the explosive charge fires when the embedded fuse burns down after a time period appropriate for the shell to reach the desired altitude. The shell usually contains a bursting charge and stars made up of cubes or spheres of material that will burn, sparkle, or explode. Multibreak shells are made up of combinations of shells designed so that the explosion of one shell ignites the next.
Shells designed to explode with a bang are called reports or salutes. The whistling effect of some devices is produced by packing techniques that cause intermittent burning. Specialized shells designed to burst forming patterns such as hearts or circles are made by surrounding the break charge with pellets containing explosive charges. When the break charge explodes, the pellets are blown outward, producing a pattern.