Gunpowder is classified as a low explosive because of its slow decomposition rate and consequently low brisance. Low explosives produce a subsonic deflagration wave rather than the supersonic detonation wave produced by brisants, or high explosives. The gases produced by burning gunpowder generate enough pressure to propel a bullet, but not enough to destroy the barrel of a firearm. This makes gunpowder less suitable for shattering rock or fortifications, where high explosives such as TNT are preferred.
Potassium nitrate is the most important ingredient in terms of both bulk and function because the combustion process releases oxygen from the potassium nitrate, promoting the rapid burning of the other ingredients. To reduce the likelihood of accidental ignition by static electricity, the granules of modern black powder are typically coated with graphite, which prevents the build-up of electrostatic charge.
The current standard composition for black powder manufactured by pyrotechnicians was adopted as long ago as 1780. It is 75% potassium nitrate, 15% softwood charcoal, and 10% sulfur. These ratios have varied over the centuries and by country, and can be altered somewhat depending on the purpose of the powder.
The burn rate of black powder can be changed by corning. Corning first compresses the fine black powder meal into blocks with a fixed density (1.7 g/cm³). The blocks are then broken up into granules. These granules are then sorted by size to give the various grades of black powder. In the USA, standard grades of black powder run from the coarse Fg grade used in large bore rifles and small cannons, through FFg (medium and smallbore arms such as muskets and fusils), FFFg (smallbore rifles and pistols), and FFFFg (extreme small bore, short pistols and most commonly for priming flintlocks). In the United Kingdom, the gunpowder grains are categorised by mesh size: the BSS sieve mesh size, being the smallest mesh size on which no grains were retained. Recognised grain sizes are Gunpowder 'G 7', 'G 20', 'G 40', and 'G 90'.
A simple, commonly cited, chemical equation for the combustion of black powder is
A more accurate, but still simplified, equation is
The products of burning do not follow any simple equation. One study's results showed that it produced (in order of descending quantities): 55.91% solid products: potassium carbonate, potassium sulfate, potassium sulfide, sulfur, potassium nitrate, potassium thiocyanate, carbon, ammonium carbonate. 42.98% gaseous products: carbon dioxide, nitrogen, carbon monoxide, hydrogen sulfide, hydrogen, methane, 1.11% water.
Black powder formulations where the nitrate used is sodium nitrate tend to be hygroscopic, unlike black powders where the nitrate used is saltpetre. Because of this, black powder which uses saltpetre can be stored unsealed and remain viable for centuries provided no liquid water is ever introduced. Muzzleloaders have been known to fire after hanging on a wall for decades in a loaded state, provided they remained dry. By contrast, powder that uses sodium nitrate, which is typically intended for blasting, must be sealed from moisture in the air to remain stable for long times.
Generally, high explosives are preferred for shattering rock. However, because of its low brisance, black powder causes fewer fractures and results in more usable stone compared to other explosives, making black powder useful for blasting monumental stone such as granite and marble.
Gunpowder can be used to make fireworks by mixing with chemical compounds that produce the desired color.
Combustion converts less than half the mass of black powder to gas. The rest ends up as a thick layer of soot inside the barrel. In addition to being a nuisance, the residue from burnt black powder is hygroscopic and an anhydrous caustic substance. When moisture from the air is absorbed, the potassium oxide or sodium oxide turns into hydroxide, which will corrode wrought iron or steel gun barrels. Black powder arms must be well cleaned both inside and out to remove the residue.
Gunpowder was discovered in China in the 9th century by Taoist monks-alchemists searching for an elixir of immortality. The discovery of gunpowder was probably the product of centuries of alchemical experimentation. Saltpetre was known to the Chinese by the mid-1st century AD and there is strong evidence of the use of saltpetre and sulfur in various largely medicinal combinations. A Chinese alchemical text from 492 noted that saltpeter gave off a purple flame when ignited, providing for the first time a practical and reliable means of distinguishing it from other inorganic salts, making it possible to evaluate and compare purification techniques.
The first reference to gunpowder is probably a passage in the Zhenyuan miaodao yaolüe, a Taoist text tentatively dated to the mid-800s:
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 wasted little time in applying gunpowder to warfare, and they produced a variety of gunpowder weapons, including flamethrowers, rockets, bombs, and mines, before inventing firearms. There was once a great deal of confusion and controversy surrounding the invention of firearms, but it is now generally accepted that firearms originated in China.
The Arabs acquired knowledge of gunpowder some time after 1240, but before 1280, by which time Hasan al-Rammah had written, in Arabic, recipes for gunpowder, instructions for the purification of saltpeter, and descriptions of gunpowder incendiaries. However, because al-Rammah attributes his material to "his father and forefathers", argues that gunpowder became prevalent in Syria and Egypt by "the end of the twelfth century or the beginning of the thirteenth".
C. F. Temler interprets Peter, Bishop of Leon, as reporting the use of cannon in Seville in 1248. Al-Hassan claims that "the first cannon in history was used by the Mamluks against the Mongols at the Battle of Ain Jalut in 1260; Khan states that it was invading Mongols who introduced gunpowder to the Islamic world and cites Mamluk antagonism towards early riflemen in their infantry as an example of how gunpowder weapons were not always met with open acceptance in the Middle East. Similarly, the refusal of their Qizilbash forces to use firearms contributed to the Safavid rout at Chaldiran in 1514.
Though the consensus is that gunpowder originated in China, others have suggested that gunpowder might possibly have been invented by the Arabs, by Roger Bacon, or by Berthold Schwarz. According to , the Arabs "had developed the first real gun, a bamboo tube reinforced with iron, which used a charge of black powder to fire an arrow" some time before 1300; however, according to , the Arabs only obtained firearms in the 1300s and all evidence points to Chinese origins.
Hasan al-Rammah included 107 gunpowder recipes in his al-furusiyyah wa al-manasib al-harbiyya (The Book of Military Horsemanship and Ingenious War Devices), 22 of which are for rockets. If one takes the median of 17 of these 22 compositions for rockets (75% nitrates, 9.06% sulphur and 15.94% carbon), it is almost identical with the reported ideal recipe (75% potassium nitrate, 10% sulphur, and 15% carbon).
The earliest extant written references to gunpowder in Europe are from the works of Roger Bacon. In Bacon's Epistola, "De Secretis Operibus Artis et Naturae et de Nullitate Magiae," dated variously between 1248 and 1257, 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 has been interpreted as an elaborate coded anagram for the quantities needed, but it may also be simply a garbled transcription of an illegible passage.
In the Opus Maior of 1267, Bacon describes firecrackers:
a child’s toy of sound and fire and explosion made in various parts of the world with powder of saltpeter, sulfur and charcoal of hazelwood.The Liber Ignium, or Book of Fires, attributed to Marcus Graecus, is a collection of incendiary recipes, including some gunpowder recipes. Partington dates the gunpowder recipes to approximately 1300. One recipe for "flying fire" (ingis volatilis) involves saltpeter, sulfur, and colophonium, which, when inserted into a reed or hollow wood, "flies away suddenly and burns up everything." Another recipe, for artificial "thunder", specifies a mixture of one pound native sulfur, two pounds linden or willow charcoal, and six pounds of saltpeter. Another specifies a 1:3:9 ratio.
Some of the gunpowder recipes in the De Mirabilibus Mundi of Albertus Magnus are identical to the recipes of the Liber Ignium, and according to Partington, "may have been taken from that work, rather than conversely." Partington suggests that some of the book may have been compiled by Albert's students, "but since it is found in thirteenth century manuscripts, it may well be by Albert." Albertus Magnus died in 1280 AD.
A major european invention was corning, which greatly increased the reliability and consistency of gunpowder. Around the late 14th century, European powdermakers began adding liquid to the constituents of gunpowder to reduce dust and with it the risk of explosion. The powdermakers would then shape the resulting paste of moistened gunpowder—known as mill cake—into "corns," or granules, to dry. Not only did "corned" powder keep better because of its reduced surface area, gunners also found that it was more powerful and easier to load into guns. The main advantage of corning is that the flame spreads between the granules, lighting them all, before significant gas expansion has occurred (when the gunpowder explodes). Without corning much of the powder away from the initial flame would be blown out of the barrel before it burnt. The size of the granules was different for different types of gun. Prior to corning, gunpowder would gradually demix into its constitutive components and was too unreliable for effective use in guns . The same granulation process is used nowadays in the pharmaceutical industry to ensure that each tablet contains the same proportion of active ingredient.
Shot and gunpowder for military purposes were made by skilled military tradesmen, who later were called firemakers, and who also were required to make fireworks for celebrations of victory or peace. During the Renaissance, two European schools of pyrotechnic thought emerged, one in Italy and the other at Nürnberg, Germany. The Italian school of pyrotechnics emphasized elaborate fireworks, and the German school stressed scientific advancement. Both schools added significantly to further development of pyrotechnics, and by the mid-17th century fireworks were used for entertainment on an unprecedented scale in Europe, being popular even at resorts and public gardens.
The introduction of smokeless powder in the late 19th century led to a contraction of the gunpowder industry.
By the early fourteenth century, according to N.J.G. Pounds's study The Medieval Castle in England and Wales, many English castles had been deserted and others were crumbling. Their military significance faded except on the borders. Gunpowder made smaller castles useless.
The English Civil War, 1642-1645, led to an expansion of the gunpowder industry, with the repeal of the Royal Patent in August 1641.
The introduction of smokeless powder in the late 19th century led to a contraction of the gunpowder industry. After the end of World War I, the majority of the British gunpowder manufacturers merged into a single company, "Explosives Trades limited"; and number of sites were closed down. This company became Nobel Industries Limited; and in 1926 became a founding member of Imperial Chemical Industries. The Home Office removed gunpowder from its list of Permitted Explosives; and shortly afterwards, on 31 December 1931, the former Curtis & Harvey's Glynneath gunpowder factory at Pontneddfechan, in Wales, closed down, and it was demolished by fire in 1932.
The last remaining gunpowder mill at the Royal Gunpowder Factory, Waltham Abbey was damaged by a German parachute mine in 1941 and it never reopened. This was followed by the closure of the gunpowder section at the Royal Ordnance Factory, ROF Chorley, the section was closed and demolished at the end of World War II; and ICI Nobel's Roslin gunpowder factory which closed in 1954.
This left the sole United Kingdom gunpowder factory at ICI Nobel's Ardeer site in Scotland; it too closed in October 1976. Since then gunpowder has been imported into the United Kingdom. In the late 1970s / early 1980s gunpowder was bought from eastern Europe, particularly from what were then East Germany and the former Yugoslavia.
It was written in the Tarikh-i Firishta (1606-1607) that the envoy of the Mongol ruler Hulegu Khan was presented with a dazzling pyrotechnics display upon his arrival in Delhi in 1258 AD. Firearms known as top-o-tufak also existed in the Vijayanagara Empire of India by as early as 1366 AD. From then on the employment of gunpowder warfare in India was prevalent, with events such as the siege of Belgaum in 1473 AD by the Sultan Muhammad Shah Bahmani.
By the 16th century, Indians were manufacturing a diverse variety of firearms; large guns in particular, became visible in Tanjore, Dacca, Bijapur and Murshidabad. Guns made of bronze were recovered from Calicut (1504) and Diu (1533). Gujarāt supplied Europe saltpeter for use in gunpowder warfare during the 17th century. Bengal and Mālwa participated in saltpeter production. The Dutch, French, Portuguese, and English used Chāpra as a center of saltpeter refining.
War rockets, mines and counter mines using gunpowder were used in India by the time of Akbar and Jahangir. Fathullah Shirazi (c. 1582), a Persian-Indian polymath and mechanical engineer who worked for Akbar the Great in the Mughal Empire, invented the autocannon, the earliest multi-shot gun. As opposed to the polybolos and repeating crossbows used earlier in ancient Greece and China, respectively, Shirazi's rapid-firing gun had multiple gun barrels that fired hand cannons loaded with gunpowder.
The ingredients are mixed as thoroughly as possible. This is achieved using a ball mill with non-sparking grinding apparatus (e.g., bronze or lead), or similar device. Historically, a marble or limestone edge runner mill, running on a limestone bed was used in Great Britain; however, by the mid 19th century this had changed to either an iron shod stone wheel or a cast iron wheel running on an iron bed. The mix is sometimes dampened with alcohol or water during grinding to prevent accidental ignition.
Around the late 14th century, European powdermakers began adding liquid to the constituents of gunpowder to reduce dust and with it the risk of explosion. The powdermakers would then shape the resulting paste of moistened gunpowder, known as mill cake, into "corns", or granules, to dry. Not only did "corned" powder keep better because of its reduced surface area, gunners also found that it was more powerful and easier to load into guns. Before long, powdermakers standardized the process by forcing mill cake through sieves instead of corning powder by hand.
During the 18th century gunpowder factories became increasingly dependent on mechanical energy.