The Slave Trade and the Growth of the British Gunpowder Industry, 1698–1808

Although Africans encountered gunpowder from the moment of European contact, the explosive remained little used until the introduction of flintlock muskets in the seventeenth century. African consumers eagerly embraced these new weapons not only for warfare but also for hunting, as status symbols, and as valuable trade items: by abolition, Britons alone annually brought approximately two hundred thousand weapons to Atlantic Africa. Over the course of the eighteenth century, the volume of powder imports used to fire these weapons increased exponentially: in 1698, the English brought just fifty-four thousand pounds of powder; by 1750, annual imports from Britain had increased sixfold. Captives were acquired with proportionately more powder from the second quarter of the eighteenth century onwards providing a further boost; in the thirty years before abolition, Africans annually acquired a million pounds of gunpowder from Britons, on average—enough ammunition to fire a musket more than twice every second throughout that thirty-year period (Figure 1).Footnote ⁶

Figure 1. Powder exported to Africa from Britain (lb.) vs. enslaved people carried from Africa in British ships (#), 1698–1808. (Sources: Powder exports are drawn from “Ledgers of Imports and Exports,” CUST3/1-82, The National Archives, Kew, United Kingdom [TNA], and “States of Navigation, Commerce and Revenue,” CUST17/1-30, TNA, which provide annual totals of the volume and value of commodities exported from Britain c.1698–1807, gunpowder included, with the exception of 1705, 1713, 1728, 1735, and 1745, the ledgers for which are not available. I have downloaded each of the digitized ledgers from the TNA catalog and then extracted powder exports into an annualized series. Numbers of people carried from Africa by Britons is from the Trans-Atlantic Slave Trade Database, “Slave Voyages,” accessed 27 Apr. 2023, www.slavevoyages.org.)

African slave sellers demanded a specific type of gunpowder that suited how they employed guns. Gunpowder is comprised of saltpeter, charcoal, and sulfur that is ground together in varying proportions (usually 70:15:15) before being graded according to its fineness. The best-quality powder was of a small grain, producing a sustained charge that was ideal for military and hunting weapons. Europeans discovered that Africans disliked such powder because it absorbed moisture easily in the topics; the explosive power of fine powder also threatened to burst the barrels of low-quality “trade guns” exported to Africa. Europeans therefore devised a specialist product known as “African,” “Guinea,” or “Trade” powder. While African powder lacked “quickness or strength,” one manufacturer observed, it was “large grained, hard dried & of a quality that will keep a long time.” Trade powder was also cheap at around half the price of the highest-graded products.Footnote ⁷

Manufacturers in south-east England—the historic center of powder making owing to the army's and navy's vociferous consumption of the explosive—initially met the demand for African powder. Powder production in London was facilitated by the capital's trading links to India, the center of global saltpeter production, and the sulfuric islands of southern Italy. By 1700, approximately twenty works surrounded London, which furnished powder to the military, but also merchants, miners, sportsmen, and wholesalers.Footnote ⁸ The London-based Royal African Company—England's largest slaving company before 1700—ordered powder from these works. The London merchants that elbowed the RAC aside at the turn of the eighteenth century continued to obtain powder from nearby mills while also purchasing the explosive from Holland, itself a major exporter of gunpowder. London mills do not appear to have been founded specifically to supply the slave trade, however; African demand was met by manufactories that also supplied a variety of buyers, especially the military.Footnote ⁹

Provincial merchants, who supplanted Londoners as the largest British slave traders in the second quarter of the eighteenth century, established new plants specifically focused on producing African powder. Bristol's slave trade grew steadily from 1698 through 1721, a period when the town's merchants laboriously imported their gunpowder from London. To open a more direct supply, a consortium of four Bristol merchants erected a new powderworks in 1722 at Woolley, a hamlet ten miles to the east of the town (Figure 2). In 1749, another consortia established a plant named Littleton in a secluded valley six miles to the southwest of Bristol. When Liverpool merchants seriously entered the slave trade in the 1730s, they sourced powder from Bristol, London, or Holland. These various sources apparently sufficed, as Liverpool's slave trade vaulted ahead of Bristol's and London's by mid-century. Limitations on the movement of powder imposed by the Board of Ordnance during the Seven Years’ War (1755–1763), including an embargo on the shipping of powder from Bristol to Liverpool in 1762, spurred the local production of powder; in 1757, four Liverpool merchants built a new powderworks at Thelwall, a village twenty miles up the River Mersey.Footnote ¹⁰ In 1764, a group of Kendal businessmen founded another new works at nearby Sedgwick, which was linked to Liverpool via ports at the mouth of the Kent River. After 1764, Liverpool's slaving merchants sourced powder from the new sites at Thelwall and Sedgwick, but also continued to purchase from London, Bristol, and Holland.Footnote ¹¹

Figure 2. Locations of the principal gunpowder works supplying Britain's slave trade, c.1722–1808.

The continued growth of the slave trade, especially at Liverpool, encouraged the further expansion of powder production. In the early 1730s, new mills were erected at Woolley, doubling capacity; once expanded, the site could grind a hundred-pound barrel of gunpowder in just two hours. Output was also increased at Littleton in the 1760s through the construction of two new mills at nearby Chew Stoke and Chew Magna. Given that Bristol's slave trade declined after 1740, this capacity was almost certainly opened to supply Liverpool's expanding trade. The northern mills were also enlarged to feed Liverpool: four expansions were made to Thelwall's output between 1764 and 1774; in 1790—the peak year for powder exports to Africa—output at Sedgwick was increased by the construction of a new set of works down the Kent River at Basingill. The growing demand for powder at Liverpool spurred the establishment in 1798 of another new plant named Low Wood, ten miles to the west of Sedgwick. Low Wood initially had two mills; in 1803, another was added to meet surging African demand. Britain's slave trade was thus supplied with gunpowder through the erection and then expansion of five new manufactories (two near Bristol, three near Liverpool) and from existing mills in London and Holland.Footnote ¹²

The establishment and then expansion of the five new works necessitated substantial capital inputs because of the multi-staged and energy-intensive nature of gunpowder making. Each site had a plant that had to be housed within numerous buildings; Sedgwick, for example, had “about twenty different buildings” including the mills, magazines, a blacksmith, cooperage, and a sawmill. Weirs, races, and “cuts” also had to be constructed to channel waterpower to the mills. Constructing a new works hence required teams of hired tradespeople to work for at least a year—a period when the investors received no income. Large sums also had to be spent on powder's three ingredients, especially saltpeter; two of the firms took out bridging loans specifically to purchase precursors.Footnote ¹³ Once a works finally produced powder, sales were made on credits that typically stretched to a year, prolonging the wait for revenue. The sums invested in setting up powder works were consequently large: Woolley's owners had sunk £9,000 into the business by 1746, and Thelwall cost £9,577, of which £3,700 was invested in the plant; £2,203 in inventory, and the remainder—including the firm's profits—circulated as credit sales. Sedgwick and Low Wood were equally as costly at £10,000 and £13,800, respectively. Establishing the five plants thus required approximately £50,000 in capital.Footnote ¹⁴

Powder works were especially capital intensive when compared to alternative investments in the Atlantic World. In 1745, for example, nine Bristol merchants fitted out the slave ship Jason Galley to drag 450 people from the Gold Coast. The vessel and its equipment cost £1,939 and the cargo added a further £2,676—£4,615 in total, or roughly half the cost of Woolley. Establishing a plant was more comparable to founding Caribbean sugar plantations, which were capital intensive because they likewise involved the semi-industrial processing of raw materials; by 1774, a typical Jamaican sugar estate with a hundred enslaved people cost £10,000. Although equivalent to Caribbean plantations, powder mills were expensive when compared to other provincial investments. In Bristol's surrounds, for example, establishing a mine or paper mill in the late eighteenth century involved approximately £2,000 of fixed capital. The powder mills were likewise some of the most capital-intensive establishments in the northwest; only coke-fired iron works and textile mills exceeded Sedgwick and Low Wood in value. The founder of Low Wood was correct when he described his plant as a “great manufactory.”Footnote ¹⁵

The large sums used to establish the five works were obtained from two principal sources: Atlantic merchants, especially slavers, and local merchant-capitalists. Each of the five firms was founded by a partnership that ranged in size from three to five individuals, with each usually investing an equal share; twenty people initially founded the firms. Most of those individuals—eleven of the twenty—had previously invested in slave ships; most continued as slavers once the works were in operation. The Cunliffe brothers Ellis (1717–1767) and Robert (1719–1778), for example, enslaved eight thousand Africans as Liverpool merchants before co-founding Thelwall. Joseph Fayrer (1743–1801), an initial investor in Low Wood, raised his capital by captaining ships that carried over four thousand people into captivity. Four of the other twenty founders were connected to the Atlantic slave economy via the bilateral colonial trade; one of the Woolley partners was previously an attorney for Caribbean plantations. The remaining five investors, all of them partners in Sedgwick or Low Wood, were local capitalists who apparently aimed to profit from Atlantic slavery without directly enslaving people. John Wakefield (1738–1811), for example, was engaged in brewing; textile making; and Caribbean trade but not the slave trade, perhaps because of his Quakerism. He nonetheless profited from enslavement by establishing, and eventually owning outright, the Sedgwick plant. Wakefield's fellow Kendal businessman Christopher Wilson Jr. (1765–1845) likewise eschewed slave ships and plantations, but enthusiastically plunged his capital into producing powder that would be bartered for slaves at Low Wood. At least two women—the widows of deceased partners—also held shares in Woolley between 1753 and 1764. The capital that financed the powderworks thus emerged principally from the Atlantic slave economy but also encompassed individuals who held themselves aloof from the bloody business of slaving.Footnote ¹⁶

These investors’ collectively expanded the geographic distribution of the British explosives industry. Prior to 1722, gunpowder manufacturing remained entirely concentrated around London; no licensed provisional mill was in permanent operation. By century's end, the erection of five new works to meet the slave trade's demand had spread powder making into south- and north-west England for the first time. The creation of this manufacturing complex enabled provincial powder makers to dominate African markets. For example, in 1767—a peace year when Britain's slave trade was buoyant—just 18 percent of gunpowder exported from London went to Africa, versus 92 percent from the outports (principally Liverpool and Bristol). Londoners instead shipped most of their powder to the Americas (47 percent of exports) Europe (19 percent), and India (17 percent). Outport merchants sent no powder to India, less than 1 percent to Europe, and just 7 percent to the Americas. The expansion of the slave trade from the metropolis to the provinces was therefore mirrored by a simultaneous expansion of manufacturing to supply that trade (Figure 3).Footnote ¹⁷

Figure 3. Gunpowder exported from Britain (lb.) versus gunpowder exported to Africa (lb.), 1772–1807. Note: The data are based on customs ledgers that provide total powder exports from Britain broken down by destination. The customs records prior to 1772 take a different format that makes it difficult to calculate the export markets for powder with the same level of precision. (Source: “States of Navigation, Commerce and Revenue,” CUST17/1-30, TNA.)

The slave trade also boosted the overall output of Britain's gunpowder industry (Figure 4). Between 1698, when detailed customs records documenting powder exports commence, and abolition in 1808, Africa absorbed at least fifty-eight million pounds of British powder—twelve percent of total production. Across that period, Africa was by far the largest export market: between 1772 and 1807, 63 percent of exported powder went to Atlantic Africa—almost three times the quantity that was shipped to the Americas, the next largest zone. Africa's importance rose over the eighteenth century: at the opening of that century, the slave trade absorbed just 5 percent of British powder production; by midcentury, Africa imported twice as much of Britain's increased output; and between 1786 and 1792—the peak of the slave trade's importance—Africa consumed a third of production. Africa was an especially significant peacetime market, with 18 percent of output headed there in peace time versus just 8 percent in war. The slave trade's significance to the powder industry reduced considerably after the 1793 outbreak of the French Revolutionary Wars, though, as output was massively increased by London mills to supply the military; in the decade before abolition, Africa once again received around 8 percent of output. The slave trade was thus certainly important for growing the overall size and extent of the British gunpowder industry during the eighteenth century, but it was by no means the primary driver of growth.

Figure 4. Total production of gunpowder (lb.) versus gunpower exported to Africa (lb.), 1698–1807. Notes: Saltpeter (which was principally imported from India) was almost entirely used for the production of gunpowder, and so the volume of powder produced in Britain can be determined by extracting the annual volumes of saltpeter imports (less any re-exports) from the customs ledgers and then multiplying those totals by 1.43—the ratio of gunpowder to its saltpeter content, by weight. The volume of powder exported to Africa annually is drawn from the same records. (Sources: “Ledgers of Imports and Exports,” CUST3/1-82, and “States of Navigation, Commerce and Revenue,” CUST17/1-30, TNA.)

Supplying the Slave Trade, c.1722–1807

British merchant-capitalists established new works because they hoped to profit by satisfying the slave trade's voracious demand for gunpowder. Earning those profits was not straightforward, though. Powder makers needed to convert their working capital into a product that had to meet the exacting standards of African consumers; sell it into a slave trade that fluctuated in volume year on year; and extend their capital, via credit sales, into a notoriously precarious business. Manufacturers who successfully navigated these myriad challenges stood to make large sums, though, offering an alternative way to profit by Atlantic slavery that bypassed the risks and moral opprobrium of owning slave ships or enslaving people.

Mill owners began the long process of earning profits by first processing saltpeter, charcoal, and sulfur into finished gunpowder. Gunpowder was a “perishable article” and so manufacturers set production targets based on forecasted African demand and ordered in precursors accordingly. Charcoal was usually obtained locally; Low Wood, for example, was supplied by wood coppiced from local forests that also fueled nearby iron furnaces. The other two ingredients came from Britain's expanding empire: sulfur was principally acquired from Sicily, where forced child laborers mined the volcanic element; and saltpeter, which comprised 70 percent of gunpowder by weight, was sourced from India via London, where the East India Company held a twice-annual auction of the substance.Footnote ¹⁸ Having obtained the ingredients, a small team of mill workers set about converting them into gunpowder. Saltpeter and sulfur were refined to remove impurities and then tumbled together with charcoal to produce a “green charge.” The charge moved into the incorporating mill—the heart of the plant—where heavy water-powered edge-runners ground the precursors together over several hours into a compacted “mill cake.” A worker then forced chunks of the cake through a series of hair sieves of increasing fineness. The largest resulting grains were graded as African powder, and the remainder were categorized by a series of Fs to indicate increasing levels of fineness: with F the lowest, followed by FF, and so on. The graded powder was “glazed” by tumbling it in barrels and then dried for at least two days, with African powder dried for a longer period to ensure durability. The finished product was loaded into one-hundred-pound barrels and stored far from the works to await shipment to Bristol or Liverpool.Footnote ¹⁹

Powder makers found customers for their finished product via agents working in Liverpool and Bristol, who were either partners within the powder-making firm or outsiders hired on commission. The two Bristol firms initially competed for local customers via their respective owners, most of whom were slaving merchants; Woolley also obtained custom in Liverpool via two agents, both slavers. In 1758, Woolley and Littleton combined their competing sales arms to form a single concern that had a permanent marketing office in the Bristol Exchange; the manufacturing arms remained distinct.Footnote ²⁰ The new firm continued to employ its Liverpool agents, who competed for business with representatives of the London and northern mills. In addition to making sales, agents also forwarded information on anticipated demand and feedback from African consumers—which could be used to set future production targets and adjust manufacturing methods. Sales agents were thus crucial links in a chain that tied British manufacturers to African buyers via slaving merchants; one agent observed that he could not sell “a single barrel” of powder if he was not “on the spot” in Liverpool.Footnote ²¹

The presence of agents from numerous gunpowder mills in the major slaving ports made for a competitive market. While Woolley and Littleton apparently enjoyed a monopoly on gunpowder sales in Bristol, competition was fierce at Liverpool, with eleven different companies selling powder there by century end. Unlike London makers, who formed a price-fixing trust, the provincial powder makers ruthlessly cut prices to gain business. Slaving merchants understood this well and they drove hard bargains by playing agents against each other. In 1801, a three-year price war erupted between the northern mills, which drove out most of the Bristol and London makers. Their competitors gone, the three northern mills sold between 80 percent and 87 percent of all the powder vended in the town between 1801 and 1807. While supplying the slave trade was a cutthroat business, specialized firms that could produce a low-priced product that met stringent African demand thus thrived. Once an agent for a powder maker secured an order, they usually sold their powder on credits extending to a year. As the slave ship departed for Africa, the powder was winched aboard from magazines at the mouths of the Mersey and Avon Rivers. Crewmen then laded the explosive into small kegs holding between a pound and twenty pounds of powder, which were used to purchase enslaved people in Africa. The ship next proceeded to the Americas, where the captives were sold, usually for bills of exchange drawn on a British banker. At the conclusion of the allotted credit period—by which time the ship had often returned—the slaving merchant finally paid for their powder, usually with a new bill of exchange drawn at three months but sometimes with bills from colonial slave sales extending to two or even three years. A year or more after the powder had been made, the manufacturer finally received revenue.Footnote ²²

Although lengthy, the completion of this cycle of production, sales, and debt collection was typically lucrative. Viewed in the aggregate profits at all the powder companies were high: Woolley returned 16 percent per annum, on average, between 1746 and 1807 (Figure 5). Profits at the other mills were equally impressive. Thelwall averaged a 21 percent annual return in its first eight years of operation, c.1761–1767; within four years of its founding, the partners had doubled their money. The accounts changed after 1768, making it difficult to track annual profits. Even so, the partners paid themselves a £900 dividend in 1774 and resolved to pay further dividends annually, indicating that the business remained healthy. After drawing out dividends, the company was still, by 1797, worth £23,959—a hefty return on the £9,577 initially subscribed. Accounts for Sedgwick show equally rapid growth: between 1788 and 1809, the company's capital value quadrupled. The nearby Low Wood works also thrived: by abolition—just eight years after the company was founded—the firm had cleared its loans and paid substantial dividends; by 1814, the partners’ capital was fully repaid via dividends, and the company was worth £34,102—almost three times the initial investment.Footnote ²³

Figure 5. Annual profits of the Woolley gunpowder works, c.1746–1807. Notes: Gaps in the data are where annual profits accounts are not extant. (Sources: “Gun Powder Annual Accounts from the Year 1746,” DD/SH/27, SHC; letters from George Dyer to Henry Strachey Jr, 1795–1801, DD/SH/27.)

While profitable in the aggregate, annual returns from powderworks fluctuated considerably, especially between peace and wartime. Although provincial powder makers did not supply the military because their product was of too low quality, the state's voracious demand for powder nonetheless bid up prices and with it the makers’ profits. Woolley's profits soared during the Seven Year's War, for example, and again during the French Revolutionary Wars; the investors made a 34.3 percent return in 1795 alone (Figure 5). The quadrupling in the capital value of Sedgwick also occurred during the French Revolutionary Wars. Although often beneficial, war was not a guarantee of success in the competitive gunpowder-making industry, though, because war also depressed the slave trade. Thelwall's profits flattened considerably during the American Revolutionary War; in 1779—a nadir for Liverpool's slave trade—the firm suffered a deep loss. Low Wood likewise made little after its initial founding during the depths of the French Revolutionary Wars; in 1799 and 1800, loans were taken out and the partners subscribed additional capital. Joseph Fayrer, the company's Liverpool-based partner and agent, feared in early 1800 that the new firm would still not “yeald a profit or Incom sufficient for me to rely upon” and so he returned to captaining slaving voyages; he died in Africa. In the same period, Woolley's profits were squeezed by a combination of the collapse of Bristol's slave trade and the loss of market share at Liverpool. Although demand from the slave trade grew in peace years, the price of powder usually fell as the state withdrew from the market. Profits in peace years could hence be low, with Woolley's investors receiving just 0.4 percent on their capital in the years 1750 and 1751, for example. Although every powder company produced healthy returns for their investors in the long run, each firm's fortunes hence fluctuated, indicating that supplying the fickle slave trade was a volatile business.Footnote ²⁴

Although fickle, the profits of manufacturing for the slave trade likely exceeded those to be made via investing in the trade itself. Annual profits from slave ship investments averaged 10 percent—a third less than the average returns reaped by Woolley's investors. Profits in the slave trade were, however, even more unpredictable than in powder making: returns ranged from bonanzas of 100 percent or more through catastrophic losses. Powder making was certainly not without risk: the African export market was highly unpredictable and the business was uniquely vulnerable to accidental explosions destroying the investors’ capital. Even so, manufacturers still made consistent returns by comparison to the slave trade; Woolley's partners, for example, never made a loss in the forty-four years for which accounts are extant. Supplying the slave trade must have thus been an important hedge against that trade's notorious risks as well as one of the most lucrative uses for provincial merchant capital.Footnote ²⁵