Conkers for Cordite: How British Children Gathered Horse Chestnuts for the Guns of 1917

In the autumn of 1917, a notice went up on the walls of classrooms and scout huts across Britain. “Groups of scholars and boy scouts are being organised to collect conkers,” it read. “This collection is invaluable war work and is very urgent. Please encourage it.”

Conkers. The glossy brown seeds of the horse chestnut, the ones British children had been drilling, threading onto string and smashing against each other in playground duels for generations. The government wanted them by the ton, it was paying for them, and it would not say what they were for.

The answer was cordite, the smokeless propellant that fired British shells and bullets. The link between a schoolboy’s conker and a naval gun ran through a shortage of one solvent, a fermenting bacterium and a Manchester chemist who would later become the first president of Israel. The scheme was real, and it did produce explosives. It also turned out to be one of the war’s more awkward experiments in home-front improvisation.

A propellant that needed a solvent

By 1914 the British Army and Royal Navy fired their guns with cordite. It was an improved version of Alfred Nobel’s 1888 “ballistite”: guncotton (nitrocellulose) mixed with nitroglycerine, plus petroleum jelly, worked into a paste and pressed through dies into long cords, which gave it its name. Britain had made it since 1889 at the Royal Gunpowder Factory at Waltham Abbey.

The ingredient that made the process work was acetone. As McGill University’s Office for Science and Society explains, acetone acted as the solvent that let the explosive components blend into a single dough that could be extruded. Then it evaporated, leaving the finished cords behind. Without it, cordite production stalled.

Before the war, acetone came mostly from the dry distillation of wood. Heat timber hard enough and the vapours contain a little of it. That was fine in peacetime. It was nowhere near enough for a war that, by 1915, was consuming shells at a rate no one had planned for. Britain’s shell shortage that year helped bring down the Liberal government and led to a new Ministry of Munitions under David Lloyd George. One of its quieter emergencies was where to find thousands of tons of solvent.

Weizmann’s bacterium

The fix came from microbiology. Since 1912 the Synthetic Products Company had been trying to make acetone and butanol by fermenting starch, and had converted an oil-cake factory at Alexandra Dock in King’s Lynn, Norfolk, for the job. The Microbiology Society’s history of the effort says the company’s results were shaky. It had trouble meeting its government contract, and in March 1916 the state nationalised the works as His Majesty’s Explosive Factory, King’s Lynn.

Chaim Weizmann, a Russian-born chemist at the University of Manchester, had been working on the same problem. He was originally after butanol, as a route to synthetic rubber. In 1914 he went looking for starch-eating bacteria in maize meal. After 100 to 150 rounds of subculturing he had a strain, now classed as Clostridium acetobutylicum, that turned starch into a mixture of acetone, butanol and ethanol. He patented it in March 1915.

The newspaper editor C. P. Scott of the Manchester Guardian introduced Weizmann to Lloyd George, and the government quickly saw what the bacterium could do. The process was scaled up to a 7,000-gallon fermenter at the Royal Naval Cordite Factory at Holton Heath in Dorset in 1916. King’s Lynn switched to the Weizmann strain in mid-1916 and then ran continuously on maize. Plants followed in Toronto and, once the United States entered the war, in Terre Haute, Indiana.

It is often said that Lloyd George rewarded Weizmann for the acetone with the 1917 Balfour Declaration, which promised British support for a Jewish national home in Palestine. Lloyd George later encouraged that version himself. Historians generally treat it as a large oversimplification, since the declaration came out of wartime diplomacy and years of Zionist lobbying, in which Weizmann’s scientific standing was only one thread.

Why the government came for the conkers

The catch was the feedstock. Weizmann’s bacterium needed starch, and the most convenient starch was maize, much of it shipped across the Atlantic. By 1917 German U-boats were sinking merchant ships at a frightening rate, and every ton of grain fed to a fermenter was a ton not fed to people. A file of the Royal Society’s Food (War) Committee, dated August 1917 to 1918, describes a scheme to collect horse chestnuts for acetone as “a plan to indirectly increase the country’s food supply by freeing the tons of cereals that were being used for this purpose.”

Horse chestnuts are inedible to people and full of starch, and Britain had plenty of horse chestnut trees in parks, lanes and school grounds. The government also tried other starch sources. According to the BBC’s World War One at Home series, it experimented “with everything from acorns to Jerusalem artichokes.”

The planning started months before the conkers fell. On 24 April 1917, according to a letter in the Royal Society’s catalogue, Sir Frederic Nathan, who ran propellant supplies for the Ministry of Munitions, wrote to the scientist William Hardy about using chestnuts for acetone. He said King’s Lynn would need 500 tons a month.

The great conker collection of 1917

That autumn, schools and scout troops were mobilised. McGill’s account says the Director of Propellant Supplies wrote to schools asking pupils to gather horse chestnuts. Historic England’s summary of the campaign says collectors were paid 7 shillings and 6 pence per hundredweight, about 50 kilograms, and the nuts were wanted without their spiky green husks.

The local records give a sense of what it looked like on the ground. A Royal Society catalogue entry dated 14 September 1917 mentions The Times publicising the appeal, villages offering prizes to the school that gathered most, and supervised groups of children wearing armbands so that they could collect on private land. In Norfolk, a local First World War history records that Queen Mary encouraged the staff at Sandringham, where horse chestnuts were plentiful, to join in. A September 1917 item in the Eastern Daily Press lists blackberries, acorns and horse chestnuts among the things being gathered.

In Lincolnshire, the 1918 annual report of the Louth Women Workers’ Association, now held by Louth Museum, records that “a Depot was opened for the collection of Horse Chestnuts, in co-operation with the Schools in Louth and District,” and that “the result was 6 tons, which were forwarded through the direction of the Minister of Propellant Supplies.” That was one market town.

Children did not need much persuading. Gathering conkers was already an autumn ritual, and now it came with money, prizes and the feeling that a sack of nuts might help a brother or father at the front. Across the country, girls and boys were also picking blackberries and gathering medicinal herbs. This was children’s war work at its most literal.

Secrecy, sacks and rotting piles

The government kept quiet about the reason. The nuts were not sent straight to the factory. Schools were told to send them to government offices in London, which forwarded them on, and the location of the plant was not publicised. The BBC put it simply: “The chestnuts were sent secretly to factories at Holton Heath and King’s Lynn.” Accounts differ on how much went where. Most of the written record points to King’s Lynn as the main user, while the Louth Museum blog, following Historic England, names Holton Heath.

The secrecy made sense in wartime. Advertising the location of a solvent plant feeding the cordite works was not a good idea, and the acetone went on to factories such as HM Factory, Gretna, on the Scottish border, where thousands of workers, most of them women, mixed what came to be called the “devil’s porridge.” But secrecy also made the logistics harder. The public was collecting with enthusiasm for a purpose it could not see, through a supply chain it could not follow.

The result was a glut. According to the Imperial War Museums’ Lives of the First World War project, children “collected more conkers than there were trains to transport them, and piles were seen rotting at railway stations.” Wet seeds sitting in sacks are not a stable raw material. A crisis-era transport system had more urgent loads than horse chestnuts.

Still, a lot of them got through. The IWM account, and a 2014 House of Commons speech, put the total that reached the Synthetic Products Company at King’s Lynn at about 3,000 tonnes. That is a striking number for a schoolchildren’s harvest. It is also well short of the 500 tons a month Nathan had hoped for in April, which would have meant 6,000 tons a year.

Why it under-delivered

The chemistry worked, but not as well as hoped. Acetone was produced from horse chestnuts, but by most accounts the conkers made a poor feedstock compared with maize. New Scientist called them poor-quality raw material, and Historic England notes that the work of stripping and processing the nuts made wider use impractical. Production from conkers at King’s Lynn reportedly started only in April 1918, and the plant is said to have closed in July of the same year. Those dates come from secondary accounts, and the factory’s exact running record is hard to pin down.

There was also no single point at which the scheme failed. The fermentation route kept running on grain, and supplies from North America filled the gap. McGill’s verdict is that “whether from corn mash or chestnuts, enough acetone was produced to meet the Allies’ demands.” The conkers were a hedge, and the hedge was only partly used.

It was not the only time wartime Britain bet on improbable materials. In the next war it seriously considered building an aircraft carrier out of frozen sawdust and ice. In the United States, a tank of molasses that gave way in Boston in 1919 had been holding feedstock for industrial alcohol, another munitions chemical. See the Great Molasses Flood.

Peach pits for gas masks in America

Britain’s conkers had an American cousin. Chemical weapons on the Western Front from 1915 made the gas mask standard kit, and the best filters used carbon made from charred fruit stones and nut shells. In September 1918, the North Carolina state archives recount, the US government asked citizens to dry and gather “seeds or pits of peaches, apricots, plums, cherries, and prunes,” along with hickory nuts, walnuts and butternuts. Schoolchildren were a particular target.

Collection barrels appeared on street corners with slogans like “Help save a soldier’s life.” By the North Carolina account, 200 peach pits or seven pounds of nuts made enough carbon for one mask filter, though other wartime figures differ. More than a hundred carloads had reached the Chemical Warfare Service by the Armistice on 11 November 1918, and the campaign was dropped almost at once. The same war economy produced the luminous dials painted by the radium girls and, in December 1917, the Halifax explosion, when a munitions ship blew up in a busy Canadian harbour.

Germany’s children went foraging too

The blockaded Central Powers went much further. Germany created a war committee for oils and fats, the Kriegsausschuss für Öle und Fette, in 1915, and appeals went out, especially to young people, to gather fruit stones, beechnuts and similar seeds that could be pressed for oil. German-language histories of the wartime collections describe schools cancelling much of their teaching from autumn 1916 so that pupils could collect. They went after nettles for fibre, cockchafers, acorns and chestnuts, among much else.

The rewards were sometimes very concrete. Children could earn honour badges in iron, silver or gold for 1,000, 2,000 or 5,000 collection stamps. In 1918, handing in a kilogram of beechnuts reportedly entitled a family to an extra 60 grams of weekly fat ration. The overall results were modest, and historians judge that many campaigns cost more effort than they returned.

Rosehips and conkers in the Second World War

When war came again, British children were sent back into the hedgerows, this time for food. On 30 July 1941, Edith Summerskill asked in the House of Commons about wild-rose hips as a source of vitamin C. The answer for the Ministry of Food was, “It is intended to encourage the use of these and other hedgerow products this autumn.” Memories collected by the BBC’s WW2 People’s War project recall children picking hips through August and September and taking them to the Women’s Voluntary Service to be made into syrup. Some accounts put the national haul in the hundreds of tons a year, though those figures are harder to verify.

Conkers were collected again too, but not for guns. Records cited by the Royal Berkshire Archives show conkers gathered in 1942 going to Macleans Ltd to extract aesculin and related compounds for laboratory and medical uses.

What the conkers tell us

It would be easy to call the 1917 campaign a failure. The conkers came in faster than the railways could take them, many rotted, and the factory ran on them for only a few months. But it was a real attempt to solve a real problem. Food was scarce, ships were being sunk, and a war that ran on chemistry had found a way to turn a children’s game into feedstock for a bacterium.

It is also a small, vivid example of something the First World War did everywhere: it pulled science, industry and ordinary life into one machine. A Manchester chemist’s microbe and a factory on a Norfolk dock connected the propellant in a naval gun to the sacks children were filling in the park. In Britain the link was kept quiet at the time. After the war, the children who had gathered them could finally hear what they had been for.

Further reading