The Devil’s Porridge

(Page created 02/05/08. Last updated 14/08/08)

The manufacture of cordite at HM Factory Gretna during World War One

By the end of the first year of the First World War the British forces were having difficulty in obtaining sufficient ammunition. The solution to the problem was to build HM Factory Gretna with the capacity to produce 800 tons per week of cordite, the propellant for shells and bullets. This was more than the combined outputs of all existing UK sources of cordite.

It was a huge undertaking, eventually stretching the nine miles from Annan to Longtown. Started in mid 1915, 15 thousand workers, mainly Irish, built the plant within a year with the first test production starting in January 1916. At its height it employed over 30,000 workers from all over the British Empire. Such a large workforce needed more accommodation than was available in the surrounding area and a new town was built, complete with high quality welfare and social facilities. Once the war was over production was quickly run down and the factory closed in 1919. Whilst all the houses were sold off, most are still standing, together with two churches, the social hall and other important buildings.

The active ingredient of cordite is nitro-glycerine. To make this highly unstable material safe to handle it was absorbed onto the surface of “nitro-cotton” – chemically charred cotton waste which became known as “gun-cotton”. When extruded and dried, the finished product resembled hemp rope, which lead to the name “cordite”.

The factory synthesised all the ingredients needed to produce cordite, and recycle as many of the reagents and solvents as possible. This meant that the factory had to accommodate a wider range of processes covering a vast area, partly to separate the processes in the interest of safety. This article will only outline the central production process.

Nitro-cotton was made by charring cotton waste with “oleum”, a mixture of concentrated nitric and sulphuric acids. The workers filled stoneware pans with the acid mixture and added the cotton to it, stirring with rakes. This process was obviously hazardous, with danger of splashing and fumes. When ready, the raw nitro-cotton was transferred into vats of boiling water to wash off excess acid. It was then scooped out of the vat and washed with cold water and powdered chalk to remove any remaining acid before being centrifuged and dried with warm air. The finished material was transported to the next stage, “paste-making”, in rubber bags.

Nitro-glycerine was synthesised by reacting glycerine with a mixture of concentrated nitric acid (HNO3) and disulphuric acid (H2S2O7), the glycerine being obtained by distilling the residues of soap-making. The glycerine and acids were gently mixed in lead cylinders and then allowed to settle, when the nitro-glycerine floated to the surface and could be skimmed off. It was then washed with a dispersion of chalk in water to remove the excess acid before being moved under gravity along lead lined troughs to the paste making room. Gravity was used as the nitro-glycerine was too unstable to pump or move about the site in containers!

In the paste making stage, employees mixed nitro-glycerine and nitro-cotton by hand on (open) lead tables shaped like shallow mixing bowls come five feet in diameter. A solvent, traditionally acetone, was added to assist with the mixing process which resulted in a cordite paste. However acetone could not initially be synthesised until later in the war, and a mixture of ethanol and ether had to be used initially. Clearly this was a very dangerous process, with health hazards in addition to the ever present threat of explosion! On a visit to the factory in 1916, Arthur Conan-Doyle (of Sherlock Holmes fame) described the paste as “The Devil’s Porridge”. The paste was pressed through leather sieves into clean rubber bags for transport about the site. Trains of bags of paste were pulled to the cordite press house by a “steamless” engine in which the steam was generated remotely from the engine.

In the cordite press house women used presses to force the paste (known as “dough”) through apertures to produce long strings of explosive. These cords were cut in length and left to dry for six days in stoves below 80 degrees F when the ether/charcoal mixture evaporates. The finished cordite strips were tested for quality and then blended in 50 ton lots for shipment to the munitions factory. Final (firing) testing was carried out on each batch at Woolwich Arsenal.

These notes by Ron Lyon summarise information on the process in a paper – “The Gretna Garrison”, published in Chemistry in Britain, March 1996, vol.32, no.3, pg.37.

The Devil’s Porridge exhibition at Eastriggs between Annan and Gretna covers both the technical and social aspects of this project. See www.devilsporridge.co.uk

See also Gretna’s Secret War by Gordon L Routledge, Bookcase, 1999