Colors and Sparks in Fireworks

Pyrotechnics were used for different ceremonial and religious purposes in China and India in the first centuries ad. A mixture of saltpeter, sulfur and charcoal was used. The Chinese made war rockets and explosives as early as the 6 century, and the craft spread to Arabia in the 7 century. The Arabs called the rockets Chinese arrows . Chinese chronicles mention the use of war rockets against the Mongol invaders in 1279. Perhaps the Mongols introduced gunpowder and rockets into Europe in the middle of the 13 century. This would be consistent with the date of the first records of their use in Europe. 

By the 17 century, elaborate displays of traditional fireworks accompanied important celebrations. In the 18 century, however, many new substances became available, materials with distinct flame colors. This opened up new possibilities for artistic fireworks. The basic phenomena of flame and color production became well established, but novel effects and novel materials still continue to be discovered. Color was given to the fire by incorporating compounds of various metals (Table 16.1). Using the names Chinese and Bengal lights retain the connection with the origin of fireworks components. 

Metals with low heat conductivity are inclined to form sparks. Titanium and zirconium have very low values, 22 and 23 W m K respectively (compared with iron 84, aluminum 236). Therefore Ti and Zr are used in modern fireworks in order to produce sparks. 

In contrast, copper has a very high heat conductivity, 400 W m K . Because of this, strong copper alloys such as berylhum copper or aluminum bronzes are used in 

Potassium nitrate (saltpeter) was the essential oxygen donor in most fireworks, while substances such as charcoal and sulfur combined with oxygen, producing heat and light. Shortly after 1800, potassium chlorate or perchlorate, still used in most fireworks mixtures, replaced potassium nitrate. Chlorine strengthens the emission 

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