Gunpowder

Smokeless powder

Gunpowder, whether black powder or smokeless powder, is a substance that burns very rapidly, releasing gases that act as a propellant in firearms. Both forms of gunpowder are low explosives. As it burns, a subsonic deflagration wave is produced rather than the supersonic detonation wave which high explosives produce. As a result, pressures generated inside a gun are sufficient to propel a bullet, but not sufficient to destroy the barrel. At the same time, this makes gunpowder less suitable for shattering rock or fortifications, applications where high explosives are preferred.

Origins

A Mongol bomb thrown against a charging Japanese samurai during the Mongol Invasions of Japan, 1281.

Gunpowder was developed in far eastern countries, notably India or China, for display at religious festivals.

Historian H.M. Elliot's Papers On the Early Use of Gunpowder in India suggests that sulfur, a principal ingredient of gunpowder, was present in the explosives used in the fiery devices mentioned in the Ramayana and Mahabharata.

The question as to the knowledge of gunpowder or any similar explosive substance, by the ancient people of India is one of great historical interest. It is clear from their medical works that they were acquainted with the constituents of gunpowder and possessed them in great abundance. Their writings make frequent references to arms of fire and rockets -- which appear to be an Indian invention, though not mentioned by name in Sanskrit writings. - Professor Wilson, director of the Royal Asiatic Society, quoted in H.M. Elliot.

Historians of gunpowder, such as Joseph Needham, sometimes use the word gunpowder to refer not only to the explosive defined at the top of this article, but also to previous concoctions of combustible material mixed with saltpeter. These early saltpeter explosives, including those made from the ancient Chinese recipes, were less powerful than black powder, but are sometimes referred to as gunpowder. Historians such as Needham, who wish to stress the early advanced state of Chinese technology, sometimes call even the earliest saltpeter explosives "gunpowder."

Saltpeter explosives were the first known chemical explosives and propellants. The facilitation of combustion by addition of saltpeter was discovered very early in China. An early record of saltpeter combustion comes from a Chinese Han era book The Kinship of the Three compiled in 142 A.D. by Wei Boyang, where he recorded experiments in which a set of ingredients were said to "fly and dance" in a violent reaction. By 300 A.D., Ge Hong, an alchemist of the Jin dynasty conclusively recorded the chemical reactions caused when saltpeter, redwood and charcoal were heated together in his book "Book of the Master of the Preservations of Solidarity". Another early record of saltpeter mixtures, a Chinese book from c. 850 A.D. called "Classified Essentials of the Mysterious Tao of the True Origin of Things," indicates that saltpeter-aided combustion was an unintended byproduct of Taoist alchemical efforts to develop an elixir of immortality:

Some have heated together sulfur, realgar and saltpeter with honey; smoke and flames result, so that their hands and faces have been burnt, and even the whole house where they were working burned down.

The Chinese used saltpeter explosives in warfare in 904 A.D., as incendiary projectiles called "flying fires." The use of saltpeter explosives was soon expanded to explosive grenades hurled from catapults. The next step was to use these mixtures as propellants. The first such use was recorded in 1132 in experiments with mortars consisting of bamboo tubes. Mortars with metal tubes (made of iron or bronze) first appeared in the wars (1268-1279) between the Mongols and the Song Dynasty.

Saltpeter combustion techniques spread to the Arabs in the 13th century.

There is no direct record of how black powder itself was invented, or how it came to be known in Europe and Asia. Most scholars believe that saltpeter explosives developed into an early form of black powder in China, and that this technology spread west from China to the Middle East and then Europe, possibly via the Silk Road. Other historians believe that several cultures contributed to the development of gunpowder, as James Partington writes in his History of Greek Fire and Gunpowder:

Gunpowder is not, of course, an 'invention' in the modern sense, the product of a single time and place; no individual's name can be attached to it, nor can that of any single nation or region. Fire is one of the primordial forces of nature, and incendiary weapons have had a place in armies' toolkits for almost as long as civilized states have made war.

The first written record of the composition of black powder, from anywhere in the world, was in Roger Bacon's "De nullitate magiæ" at Oxford in 1234.

In Bacon's "De Secretis Operibus Artis et Naturae" in 1248, he states:

We can, with saltpeter and other substances, compose artificially a fire that can be launched over long distances... By only using a very small quantity of this material much light can be created accompanied by a horrible fracas. It is possible with it to destroy a town or an army ... In order to produce this artificial lightning and thunder it is necessary to take saltpeter, sulfur, and Luru Vopo Vir Can Utriet.

The last part is probably some sort of coded anagram for the quantities needed. In the Opus Maior he describes firecrackers around 1267:

"a child’s toy of sound and fire made in various parts of the world with powder of saltpeter, sulphur and charcoal of hazelwood."

Bacon does not, however, claim to have invented black powder, and his reference to "various parts of the world" implies that the black powder was already widespread when he was writing.

The first Chinese recipe for black powder given by Needham is from 1628, almost four hundred year's after Roger Bacon's book. It comes from a book called the Wu Pei Chih, which lists all the saltpeter explosive recipes from the 1606 Ping Lu, but includes exactly one new mixture, for "lead bullet gunpowder" (chhien chhung huo yao), composed of 40 oz. of saltpeter, 6 oz. of sulphur, and 6.8 oz. of charcoal. As Needham observes, "The explosive is used here as a charge of black powder."

The process of "corning" black powder was a further important improvement, and was developed in Europe probably during the late 14th century. Corning involves forcing damp powder through a sieve to form it into granules which harden when dry, preventing the component ingredients of gunpowder from separating over time, thus making it far more reliable and consistent. It also allowed for more powerful and faster ignition, since the spaces between the particles allowed for oxygen necessary for speedy combustion. However, the prevalence of superstitious belief in alchemy and magic commonly led, at least in the early days of firearms, to the adulteration of the mixture with exotic, but of course deleterious products, usually mercury salts, arsenic and amber.

Composition

Black powder is a mixture of saltpeter (potassium nitrate or, less frequently, sodium nitrate), charcoal and sulfur with a ratio (by weight) of approximately 15:3:2 respectively. Modern black powder also typically has a small amount of graphite added to it, to reduce the likelihood of static electricity causing loose black powder to ignite. The ratio has changed over the centuries of its use, and can be altered somewhat depending on the purpose of the powder. Historically, potassium nitrate was extracted from manure by a process superficially similar to composting. "Nitre beds" took about a year to produce crystallized potassium nitrate. It could also be mined from caves with high concentrations of potassium nitrate, often resulting from the residue from bat dung accumulating over millennia.

Versions of unburnt black powder containing potassium nitrate are not hygroscopic, although versions of black powder containing sodium nitrate tend to be slightly hygroscopic. Because of this, the most common form of black powder containing potassium nitrate can be stored in unsealed powder flasks for very long periods of time, measured in centuries, provided no liquid water is ever introduced, while remaining viable. Similarly, muzzleloaders have been known to fire with a trigger pull many decades after being loaded, after being hung on a wall during an earlier era in a loaded state, provided they are kept dry. In contrast, versions of black powder or gunpowder intended for blasting contain sodium nitrate, and are not known for being as stable over such long periods of time, unless sealed from the moisture in the air.

Residue from burnt black powder, in contrast to unburnt black powder, is hygroscopic, and thus fired black powder residue proves extremely harmful to the steel in guns and gun barrels because it forms corrosive alkalis as moisture is taken into the burnt black powder residue, which typically weigh slightly more than 50% of the unburnt black powder weight.

Characteristics and use

Gunpowder is not classified as a high explosive because it has a very slow decomposition rate and therefore a very low brisance. This same property that makes it a poor explosive makes it useful as a propellant — the lack of brisance keeps the black powder from shattering a gun barrel, and directs the energy to propelling the bullet.

The main disadvantages of black powder are a relatively low energy density (compared to modern smokeless powders) and the extremely large quantities of soot left behind. During the combustion process, less than half of black powder is converted to gas. The rest ends up as a thick layer of soot inside the barrel and a dense cloud of white smoke. In addition to being a nuisance, the residue in the barrel is hygroscopic and an anhydrous caustic substance. When moisture from the air is absorbed, the potassium oxide or sodium oxide turn into hydroxides, which will corrode wrought iron or steel gun barrels. Black powder arms must be well cleaned inside and out after firing to remove the residue. The thick smoke of black powder is also a tactical disadvantage, as it can quickly become so opaque as to impair aiming; it also reveals the shooter's position.

The size of the granule of powder and the confinement determine the burn rate of black powder. Finer grains result in greater surface area, which results in a faster burn. Tight confinement in the barrel causes a column of black powder to explode, which is the desired result. Not seating the bullet firmly against the powder column can result in a harmonic shockwave, which can create a dangerous over-pressure condition and damage the gun barrel. One of the advantages of black powder is that precise loading of the charge is not as vital as with smokeless powder firearms and is carried out using volumetric measures rather than precise weight. However, damage to a gun and its shooter due to overloading is still possible.

Black powder is well suited for blank rounds, signal flares, and rescue line launches.

Additionally, the low brisance of black powder made it useful when blasting monumental stone such as granite and marble. Black powder caused fewer fractures when compared to other explosives, with the result that more of the quarried stone could be used. Gunpowder is used to make fireworks by mixing with chemical elements that produce the desired color.

References

• Ebrey, Patricia Buckley (1999). The Cambridge Illustrated History of China. Cambridge University Press. ISBN 0-521-66991-X.
• Partington, James Riddick (1998). A History of Greek Fire and Gunpowder. The Johns Hopkins University Press. ISBN 0-8018-5954-9.
• Liang, Jieming (2006). Chinese Siege Warfare: Mechanical Artillery & Siege Weapons of Antiquity. ISBN 981-05-5380-3.

See also

• Four Great Inventions of Ancient China
• List of Chinese inventions
• Firework
• Greek fire
• Gunpowder Plot
• Cannon
• Musket
• Arquebus
• Guns
• Firearms
• Brown powder
• Gonne
• W231

External links

• Gun and Gunpowder
• The Origins of Gunpowder
• Cannons and Gunpowder
• History of Science and Technology in Islam
• Ulrich Bretschler's Gunpowder Chemistry page
• Oare Gunpowder Works, Kent, UK
• Royal Gunpowder Mills
• Chinese Siege Warfare: Mechanical Artillery and Siege Weapons of Antiquity - An Illustrated History