Middle Era

Part 10 - Gunpowder

The Chinese knew about Saltpeter in the 1st century CE but gunpowder, the first chemical explosive, was not discovered until the 9th century CE, when Chinese alchemists were looking for the elixir of life (Its Chinese name, huoyao, means, 'fire medicine').

From about 1000 CE, the Chinese started to produce gunpowder by combining saltpeter, sulfur and carbon. It was used for fireworks and fire crackers attached to spears for a shock burst or used for rocket propelled arrows that could be shot off in large salvos without using archers. It was later using in bombs, mines, fire projectors and guns and, by the 13th century, the technology had revolutionized warfare throughout Asia and Europe.

The earliest recipe, from the 11th century Song dynasty, contained charcoal as the fuel and potassium nitrate (saltpeter) to supply oxygen and sulfur to reduce the temperature for rapid combustion. However, the recipes contained less than 50% saltpeter so they were used as incendiaries and fireworks rather than explosives.

By 1083 the Chinese were making hundreds of thousands of fire arrows for the garrisons of their walled cities. The first proto-guns, known as "fire lances," were used during the siege of De'an (modern Anlu in eastern Hubei) in 1132 CE. The first bamboo and paper gun barrels were later replaced with metal and, in 1163, Chinese general Wei Sheng, using dozens of war chariots loaded with metal firearms, claimed a great victory against the Manchus.

In the 13th century, the Jin dynasty armies started using iron-cased bombs and fire lances firing multiple bullets. The true gun, the hand cannon, appeared in 1287 CE.

The Chinese army was the first to use torpedos and anti-ship rocket missiles, against Japanese pirates, during the Ming Dynasty (1368 – 1644).  However, from the 17th century, the Manchu rulers banned the use of firearms in China permitting only the use of traditional weapons until the middle of 19th century.

The Persians named potassium nitrate, "Chinese salt" while in Arabic it was known as, 'Snow from China' or, "salt from Chinese salt marshes". Chinese gunpowder weapons may have been used by the Mongols at the Battle of Mohi in 1241, in Hungary, one of the main battles during the Mongol invasion of Europe. 

The earliest European accounts of gunpowder appear in 13th century England when Roger Bacon referred to what might have been firecrackers although his gunpowder recipe may have been suitable for hand-cannons. Bacon wrote, " . . . a device no bigger than one's thumb. From the violence of that salt called saltpeter, so horrible a sound is made by the bursting . . . that we find the ear assaulted by a noise exceeding the roar of strong thunder, and a flash brighter than the most brilliant lightning."

In the late 14th century wet grinding of the gunpowder improved safety and the moist paste was rolled into balls before drying. This also prevented dry ingredients from separating (a technique still used by modern pharmaceutical manufacturers). The gunpowder balls absorbed less water from the air during storage and travelled better but they had to be crushed by the gunner immediately before use. This produced uneven particle sizes and unpredictable results. Fine gunpowder often caused cannons to burst because of the initial spike in pressure before the cannonball was forced down the barrel.

Gun makers discovered that fire spread from grain to grain quicker if the gunpowder was formed into grains similar in size to wheat (corn) seeds. This "corned" gunpowder was from up to 300% more powerful (34 pounds of fine serpentine gunpowder was needed to shoot a 47-pound ball, but only 18 pounds of corned powder). The optimum size of the grain depended on its use; larger for large cannon, finer for small arms. Corned powder also retained the advantage of low moisture absorption, as even small grains still had much less surface area to attract water than a fine, floury powder.

European manufacturers also began purifying saltpeter, using wood ashes containing potassium carbonate to precipitate calcium from their dung liquor, and using ox blood, alum, and slices of turnip to clarify the solution.

By mid-17th century, in Europe, fireworks were used increasingly for entertainment which stimulating chemical research.

The damp paste was formed into corn-sized grains by hand, or with the use of a sieve. After 1800, the damp mill-cake was pressed in molds to extract the liquid and increase the density. When dry, the hard cakes were broken up and the particles sorted with sieves into uniform sizes. Coarse powders were used in cannons with finer powders used for muskets. The finest gun powders were used for small hand guns and for priming.

Gunpowder revolutionized European warfare. The cannon replaced the trebuchet catapult as the main weapon for siege warfare and formations of musketeers, protected by pikemen, dominated battlefields.

In 1774 France, Louis XVI established a Gunpowder Administration, headed by Antoine Lavoisier who started a program to increase saltpeter production from traditional dung heaps. He researched best refining and powder manufacturing methods, improved management, record-keeping and pricing that encouraged private investment. In only a year, France had enough gunpowder to supply the American revolutionary war of independence against Britain. By careful testing of the proportions and grinding time, powder from French mills became the best in the world by 1788.

In the 19th century, Lammot du Pont and Thomas Rodman developed a gunpowder for cannon used during the American Civil War. The grains were about 0.6 inches (15 mm) in diameter. Even larger grains the size of golf and tennis balls were used in 20-inch (51 cm) Rodman guns. In 1875 DuPont introduced powder, pressed into a hexagonal shape, about 1.5 inches (3.8 cm) diameter with a small centre hole, for larger guns. 

 Charcoal quality also improved with the use of wood from the Pacific willow and in Great Britain alder buckthorn. The traditional manufacturing technique (of burning wood in earthen pits with a limited air supply) was replaced by baking wood in heated iron containers which produced a more consistent product. Sulphur was obtained from volcanoes.

In 1863, DuPont chemists developed a process to make potassium nitrate using sodium nitrate, from Chilean mines, and potassium chloride.

The modern standard composition for black powders has been used since 1780. Proportions by weight 75% potassium nitrate (KNO3), 15% softwood charcoal (C), and 10% sulfur (S).Blasting powder with 70% nitrate, 14% charcoal, and 16% sulfur; contained the cheaper sodium nitrate in place of potassium nitrate with proportions as low as 40% nitrate, 30% charcoal, and 30% sulfur. In 1857, Lammot du Pont produced blasting powder with the powder grains coated with graphite, which not only reduced moisture absorption but also the risk of an accidental explosion caused by static electricity.

In 1879, the composition of French war powder was 75% saltpeter, 12.5% charcoal, 12.5% sulfur. The British used a similar ratio except for Congreve rockets which used 62.4% saltpeter, 23.2% charcoal and 14.4% sulfur.