Scheduled Monument: Royal Naval Cordite Factory at Holton Heath (1019151)

EXTRACT FROM ENGLISH HERITAGE'S RECORD OF SCHEDULED MONUMENTS MONUMENT: Royal Naval Cordite Factory at Holton Heath PARISH: WAREHAM ST MARTIN DISTRICT: PURBECK COUNTY: DORSET NATIONAL MONUMENT NO: 33181 NATIONAL GRID REFERENCE(S): SY94559043 SY94409090 SY94649086 SY95159155 SY95619105 DESCRIPTION OF THE MONUMENT The monument, which falls into five separate areas of protection, includes those parts of the former Royal Naval Cordite Factory (RNCF) at Holton Heath which display the best surviving remains, representing the key industrial processes undertaken at RNCF. The factory originally covered an area of about 200ha, predominantly on heathland, around a group of low hills on the north western edge of Poole Harbour. Much of the southern part of the site is now occupied by an industrial estate. During World War II, the factory was protected by a group of anti-aircraft batteries and a bombing decoy site established to the south. These lie outside the main factory complex and surviving examples are the subjects of separate schedulings. In 1914, Winston Churchill (then First Lord of The Admiralty) commissioned a plant to provide the Royal Navy with an independent supply of high quality cordite as a propellant for shells. The cordite was manufactured by mixing nitroglycerine (a dense and colourless liquid) and guncotton (a fibrous solid). These ingredients are volatile and highly explosive in nature and their production required a remote and secure location. The site at Holton Heath met these requirements and also had the advantage of a coastal location and good communications inland, connecting it with, for example, the principal naval bases at Chatham, Portsmouth and Devonport. Construction began in 1915 and the factory opened in January 1916. The site was enclosed by an outer fence and access strictly regulated through the main gates situated on the site's western side. During World War II two pillboxes were constructed, one at either end of the road which ran along the northern side of the factory; the eastern example survives and is included in the scheduling. Three main production areas can be identified within the factory. These include the acetone plant within the south western area (33181/01); the nitration plant and cordite press plant within the central area (33183/03); and the cordite drying plant and picrites factory to the east (area 33181/04). All were contained within the so-called `Danger Area'; a fenced compound which housed all structures involved in the production, processing and handling of explosive material. An area in the north west of the complex contained the general offices and laboratories, set around a courtyard. This area lies outside the area of scheduling, although the buildings are seperately recommended for Listing at Grade II. To the west of the main factory complex, a separate square fenced compound contained an experimental area where cordite was tested under a variety of atmospheric conditions; this area lies outside the area of scheduling. In addition to these areas of protection, two further areas are included in the scheduling: area 33181/05 includes a reservoir at the south east of the site, and area 33181/02 includes the control trench and associated air raid shalters from which defence of the factory site was coordinated. Within the factory over 120 buildings lay within the Danger Area. These `Danger Buildings' were each identified by a letter code and, if not a unique structure, a following number. The Danger Buildings at Holton Heath were mainly of flimsy construction at first, mostly composed of matchboarding with wooden roofs covered in a rubberoid material which would, in the event of an explosion, extinguish themselves when projected through the air. The floors were often covered in asphalt (except in the nitrator plant where lead was used). All Danger Buildings had to be set at prescribed distances from other structures and earthen mounds were constructed around their periphery in order to prevent explosive waves from travelling horizontally between them. The mounds were typically 6m to 8m wide at the base and usually built to the same height as the enclosed building. The mounds were turfed in order to retain the sandy soil, and this gave the site an almost park-like appearance. The acetone factory was situated to the north of the railway station within the south western area of the site (area 33181/01). Acetone was important for incorporating the principal ingredients during cordite production, but a world shortage during World War I meant that the factory required its own supply. The plant was built by 1917 and production employed novel fermentation technology using maize as a starch source. The factory included a brick granary which housed the maize for production. Maize was initially imported from the USA, but during the peak U-boat campaign these imports were disrupted and other materials including artichokes, horse chestnuts and even acorns were temporarily employed as alternatives. The cooker house on the eastern side of the plant is a large two storeyed structure which originally contained six cookers. Here, the maize was reduced to a mash and transported to the eight fermentation vessels which were composed of aluminium and housed within reinforced concrete tanks. Six of the concrete tanks survive and each is 10m in diameter and about 4m high. These were originally housed within the structure of the main factory building, the largest within the RNCF complex. A change to the production of flashless cordite in the later 1920s reduced the need for acetone. From this time the plant was disused and the small quantities of acetone now required were imported to the site. As a result the granary was demolished while the cooker house was converted into workshops and offices; the cooker house is Listed Grade II and overlies part of the scheduled area. The concrete tanks were later converted for use as air raid shelters during World War II. Nitroglycerine (NG) production involved adding nitric and sulphuric acid with glycerene (which was imported to the site). This process took place within a nitration plant located within the central area of the factory complex (area 33181/03). A plan of 1922 shows that the plant initially consisted of a charge house, a nitrator-separator, a washing house and a wash water settling house. The production method employed a process which involved mixing batches of nitroglycerine. The floors of all NG production houses were lined with lead (which was acid resistant and too soft to strike sparks) and lighting was provided by electrical lights mounted externally to shine through windows. On 23rd June 1931 a major accident occurred when a charge of NG blew up and destroyed the nitrator house and charge house. The filter house and mixing house were also destroyed as the explosion spread via the guttering linking the structures. The accident killed ten staff, including the chief chemist and a senior engineer and severely disrupted production. The nitrator plant was rebuilt using the `Schmid System' which was installed by German engineers. This system produced a continuous supply of NG rather than batches as before. The new nitrator-separator house was built on the same site, but the lower half was now set below ground level. The wooden two storey building was encased within a concrete structure which was reinforced with steel bars. The whole structure was then covered by 11m of earth and the resulting artificial mound became known as `Nitroglycerine Hill'. The structure was designed to provide protection against aerial attacks, lightning strikes and any internal explosion. Additional safety was provided by the means to flood the interior in the event of an emergency. This plant was supplied with mixed acids via tanks contained in a brick structure to the north. A control trench designed for the coordination of defence during airborne attack, an associated storage building and a group of air raid shelters are located a short distance to the west, within a separate area (33181/02). Guncotton, which was mixed with the NG to produce cordite, was initially produced by using waste cotton as a raw material. This was dipped in acid in earthenware pans arranged in groups of four and then boiled in wooden vats before being pulped. The guncotton was then washed in vessels known as `poachers', where it was allowed to settle before being sent to drying houses, which were buildings of light wooden construction fitted with internal shelving. From the later 1920s, the process was modified with shredded paper being used instead of cotton. During the 1930s, the mixture was made into a slurry and pumped around the mixing houses in channels. The rolling houses and drying houses at RNCF have since been removed and their sites are now occupied by the industrial estate; this area is not included within the scheduling. Following the manufacture of the main ingredients, cordite production proper could begin. Three methods of cordite manufacture were used throughout the production period at Holton Heath. Initially, quantities of dry guncotton were placed in rubberised bags and added to nitroglycerine. This was then poured onto lead tables, kneeded by hand, sieved and taken to the incorporating houses, where acetone was added and a jelly-like material produced. It was then passed through hydraulic presses in the press houses in order to produce a cord-like material, from which measured lengths could be cut. The material was later dried in the cordite drying plant situated within the north eastern area of the site (area 33181/04). The cordite was finally transported to Rocklea Jetty, to the south east of the factory site, from where it was taken by barge to Priddy's Hard at Gosport in Hampshire or Upnor Castle at Medway in Kent. From 1927 a solventless `Cordite SC' was produced using a mixture of NG and NC (material with a nitrogen content of less than 13%). This was turned into a paste and pumped to a mixing house, where excess water was removed by presses. The resulting paste was passed through rollers in order to create a jelly. This allowed production of sheets of cordite, which were cut into squares and further consolidated in the press houses. This process produced a more highly explosive cordite and following a number of accidents a new form of press house was developed which included three separate structures for the operatives, motors and presses, with each building separated by earthen banks. The new structures gradually replaced the older drying stove sites. During the 1940s, large presses were introduced to produce rocket propellant and catapult cordite. These were also housed in new buildings, which occupied old press house sites. These were much larger and of a new construction composed of reinforced concrete, with steel frames and an interior of glazed brick. These press rooms were covered by a large earthen mound which was subsequently turfed. A number of these structures are included in the scheduling representing the diversity of types present at the site. The use of cordite SC produced an enormous flash during firing which gave away the position of guns. In order to prevent this, picrites were added and a `flashless' cordite produced. A picrites factory was built within the complex in 1937; this plant included about 20 structures and it achieved maximum production from 1939. The site of this plant has survived and is included in area 33181/04 of the scheduling. Tetryl was the only product manufactured at Holton Heath which was not used for cordite production. This pale yellow crystalline material, used to detonate shells and bombs, was manufactured here because its main ingredients (sulphuric acid, nitric acid and acetone) were all produced on site. The tetryl factory was situated within the central southern area, close to the acids plant, but has since been demolished, and the site is now overlain by the industrial estate. The large size of the factory site determined the need for extensive movement of material and equipment. As a result, a number of transport networks were developed for this purpose. These included a standard gauge rail network, which served to enable access of equipment and raw materials into the factory complex from the mainline railway. Within the complex itself, a narrow gauge rail network served all buildings associated with the production of cordite. Initially, some use was made of guttering in order to enable liquid NG to travel, assisted by gravity, between various production plants. However, after the accident of 1931, NG was transported between the plants by means of trolleys with rubber tyres. Water was suppied to the factory from the River Stour, about 10 miles to the north, by means of a pumping house at Corfe Mullen. The main reservoir is situated within the centre of the site, relatively close to Nitroglycerine Hill, and lies in area 33181/03. This structure was divided into two areas and both were eventually covered. This reservoir served the complex without a problem. However, a second smaller reservoir was constructed within the south eastern area, in order to provide a reserve supply in the event of an emergency or failure of the main supply. This lies in the area 33181/05. During World War II, a borehole was dug and a local water supply was also established in case of failure of the main supply. Cordite manufacture at RNCF ended in 1946, while picrites and tetryl production continued on an intermittent basis until 1957, when production at RNCF finally ended. All gate and fence posts relating to land boundaries and the structure of the cooker house, which is Listed Grade II, are excluded from the scheduling, although the ground beneath these features is included. ASSESSMENT OF IMPORTANCE The Royal Naval Cordite Factory (RNCF) at Holton Heath represents the first purpose-built site for cordite production in the United Kingdom and the only such site built and managed by the Royal Navy. The range and complexity of manufacturing processes conducted at Holton Heath required a variety of production plants, many of which survive well providing evidence for construction techniques and technology. The nitration plant represents the heart of the Nitroglycerine (NG) production process. `Nitroglycerine Hill' is key to this and, by virtue of its size and central location, dominates the entire site. Despite the removal of the wooden structure and lead floor from the interior, the internal concrete structure and artificial mound survive well, while the infilling of the interior with earth and blocking of the entrance tunnels has sealed the foundation levels. Other surviving remains within the nitration plant include the sites of wash houses to the south and a brick building which contained a large tank which supplied the Nitroglycerine Hill complex with mixed acids during World War II. This structure is situated between Nitroglycerine Hill and the reservoir to the north west. The acetone factory represents the first purpose-built industrial plant in the United Kingdom designed for the application of a `biotechnology'. It was the first to employ the fermentation technology developed by Chaim Weizmann (who was later to become the first president of Israel) and this introduced laboratory-like sterility into an industrial process for the first time. This plant was to provide a model upon which others were based, including plants at Terre Haute in Indiana, Toronto in Canada and Nazik in India. Despite the partial demolition of the acetone factory at Holton Heath during the mid-1930s, many elements remain intact. The six surviving reinforced concrete tanks (which contained the fermentation vessels) are especially unusual, as this material was very rarely used in the construction of chemical plants at this time. This survival is complemented by associated features such as the cooker house, railway embankment and associated tramlines. In addition it is possible to trace the foundations of the whole complex on the ground. RNCF Holton Heath pioneered the technological development of cordite within the United Kingdom from 1916 during a period of great demand towards the end of World War I. This process continued throughout the 1920s and 1930s. The technology developed at Holton Heath also made an important contribution to the war effort during the period 1939-1945. The Holton Heath complex is a rare survival in Britain of a purpose-built munitions factory constructed during World War I. Earlier sites such as the important complex at Waltham Abbey in Essex, were based on gunpowder production and were very different in form and development. Later sites, such as the Royal Naval Propellants Factory at Caerwent in South Wales, built in 1938 benefitted from the technology gained at Holton Heath and represents the `next generation' of this type of site. MONUMENT INCLUDED IN THE SCHEDULE ON 25th June 2001

Record last edited

Sep 13 2024 11:28AM