An early rocket firework called the earth rat once startled a Chinese empress
At a feast given in her honour by Emperor Lizong in the 13th century, Empress Dowager Gong Sheng was badly startled when a dilaoshu, or earth rat, went off near her. This scurrying, self-propelled firework was one of the earliest known uses of rocket propulsion, and it came from a tradition of Chinese pyrotechnics stretching back over a thousand years.
The story begins with bamboo. During the Han dynasty, people tossed bamboo stems into fires to make them burst with a bang. Later, gunpowder stuffed into small containers imitated the sound, and in the Song dynasty, between 960 and 1279, makers rolled paper tubes filled with powder and a fuse, then strung them into long chains called whips that crackled off one after another. Ordinary people bought firecrackers from market stalls, and in 1110 the army staged a grand display for Emperor Huizong.
Colour was China's great secret. Recipes recorded over centuries tinted flames and smoke with compounds such as arsenic sulphide for yellow and copper acetate for green. European visitors were dazzled; an envoy of Peter the Great reported fireworks unlike anything seen in Europe. In 1758 a Jesuit living in Beijing, Pierre d'Incarville, sent a description of Chinese methods to the Paris Academy of Sciences. European chemistry caught up after 1786, when Berthollet found that potassium chlorate produced violet light, followed by brilliant colours from barium, strontium and copper chlorates and dazzling silver from newly isolated magnesium and aluminium.
Colour comes from pellets called stars, which pack an oxidiser, a fuel, colouring salts and a binder. The brightest use aluminium, often alloyed with magnesium as magnalium. Sparks are more limited: glowing solid particles can only shine red to orange, yellow to gold or white to silver, because their light comes from heat rather than from a specific element burning as vapour.
Displays rely mainly on aerial shells fired from mortars, and their bursts have names. A peony throws many small tailless stars a short way; a dahlia uses fewer, larger stars flying farther. A willow droops in long gold trails, and a crossette's stars split apart to make a crisscross grid. A single cake of linked tubes can fire more than 1,000 shots. China still makes and exports more fireworks than any other country.
Source: Fireworks
