Editing Gunpowder (section)

== Production ==
{{main|Powder mill}}
[[File:Irvinepowderhouse2.JPG|thumb|upright=0.8|left|The old Powder or Pouther magazine dating from 1642, built by order of [[Charles I of England|Charles I]]. [[Irvine, Ayrshire|Irvine]], [[North Ayrshire]], Scotland]]

For the most powerful black powder, [[meal powder]], a [[wood]] charcoal is used. The best wood for the purpose is Pacific [[willow]],<ref>{{cite book|author=US Department of Agriculture|title=Department Bulleting No. 316: Willows: Their growth, use, and importance |year=1917|page=31|url=https://books.google.com/books?id=x20TAAAAYAAJ&q=black+powder+willow&pg=RA15-PA31|publisher=The Department}}</ref> but others such as [[alder]] or [[buckthorn]] can be used. In Great Britain between the 15th and 19th centuries charcoal from [[alder buckthorn]] was greatly prized for gunpowder manufacture; [[Populus sect. Aigeiros|cottonwood]] was used by the American [[Confederate States]].{{sfn|Kelly|2004|p=200}} The ingredients are reduced in particle size and mixed as intimately as possible. Originally, this was with a mortar-and-pestle or a similarly operating stamping-mill, using copper, bronze or other non-sparking materials, until supplanted by the rotating [[ball mill]] principle with non-sparking [[bronze]] or [[lead]]. 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.<ref name="earl-2" /> The mix was dampened with [[ethanol|alcohol]] or water during grinding to prevent accidental ignition. This also helps the extremely soluble saltpeter to mix into the microscopic pores of the very high surface-area charcoal.

[[File:Hagley Mill Equipment.jpg|thumb|Edge-runner mill in a restored mill, at [[Hagley Museum and Library|The Hagley Museum]]]]
[[File:Martello Tower barrels.jpg|thumb|Gunpowder storing barrels at the [[Martello tower]] in [[Point Pleasant Park]], [[Halifax, Nova Scotia]], Canada]]
[[File:Barout khaneh near Tehran by Eugène Flandin.jpg|thumb|right|1840 drawing of a [[gunpowder magazine]] near [[Tehran]], [[Persia]]. Gunpowder was extensively used in the [[Naderian Wars]].]]
Around the late 14th century, European powdermakers first began adding liquid during grinding to improve mixing, reduce dust, and with it the risk of explosion.{{sfn|Kelly|2004|pp=60–63}} The powder-makers would then shape the resulting paste of dampened gunpowder, known as mill cake, into corns, or grains, 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, powder-makers standardized the process by forcing mill cake through sieves instead of corning powder by hand.

The improvement was based on reducing the surface area of a higher density composition. At the beginning of the 19th century, makers increased density further by static pressing. They shoveled damp mill cake into a two-foot square box, placed this beneath a screw press and reduced it to half its volume. "Press cake" had the hardness of [[slate]]. They broke the dried slabs with hammers or rollers, and sorted the granules with sieves into different grades.  In the United States, [[Eleuthere Irenee du Pont]], who had learned the trade from Lavoisier, tumbled the dried grains in rotating barrels to round the edges and increase durability during shipping and handling. (Sharp grains rounded off in transport, producing fine "meal dust" that changed the burning properties.)

Another advance was the manufacture of kiln charcoal by distilling wood in heated iron retorts instead of burning it in earthen pits. Controlling the temperature influenced the power and consistency of the finished gunpowder.  In 1863, in response to high prices for Indian saltpeter, [[DuPont]] chemists developed a process using [[potash]] or mined [[potassium chloride]] to convert plentiful [[Chile]]an sodium nitrate to potassium nitrate.{{sfn|Kelly|2004|p=199}}

The following year (1864) the Gatebeck Low Gunpowder Works in Cumbria (Great Britain) started a plant to manufacture potassium nitrate by essentially the same chemical process.<ref>{{cite journal |last1=Jecock |first1=Marcus |last2=Dunn |first2= Christopher |title=Gatebeck Low Gunpowder Works and the Workers' Settlements of Endmoor and Gatebeck, Cumbria |journal=Research Department Report Series|publisher=[[English Heritage]] |date=2009 |volume=63 |issn=1749-8775 |display-authors=etal}}</ref> This is nowadays called the 'Wakefield Process', after the owners of the company. It would have used potassium chloride from the Staßfurt mines, near Magdeburg, Germany, which had recently become available in industrial quantities.<ref>{{cite web|last1=Heller|first1=Cornelia|title=Stassfurt|url=http://www.fad.cat/citytocity/2/cat/wp-content/uploads/guanyadora/booklet_stassfurt.pdf |archive-url=https://web.archive.org/web/20120619094334/http://www.fad.cat/citytocity/2/cat/wp-content/uploads/guanyadora/booklet_stassfurt.pdf |archive-date=2012-06-19 |url-status=live|website=STASSFURT – FAD|publisher=Ministry of Regional Development and Transport Saxony-Anhalt|access-date=27 May 2015|page=10|date=December 2009}}</ref>

During the 18th century, gunpowder factories became increasingly dependent on mechanical energy.<ref>{{cite book |editor-last=Frängsmyr |editor-first=Tore |editor-first2=J.L. |editor-last2=Heilbron |editor-first3=Robin E. |editor-last3=Rider |title=The Quantifying Spirit in the Eighteenth Century |location=Berkeley |publisher=University of California Press |date=1990 |url= http://ark.cdlib.org/ark:/13030/ft6d5nb455/ |page=292}}</ref> Despite mechanization, production difficulties related to humidity control, especially during the pressing, were still present in the late 19th century. A paper from 1885 laments that "Gunpowder is such a nervous and sensitive spirit, that in almost every process of manufacture it changes under our hands as the weather changes." Pressing times to the desired density could vary by a factor of three depending on the atmospheric humidity.<ref>C.E. Munroe (1885) "Notes on the literature of explosives no. VIII", Proceedings of the US Naval Institute, no. XI, p. 285</ref>