The Royal Ordnance Factory
Bridgend South Wales
  The Task Ahead
  The End of War

Gun Cotton Production at the Bridgend Royal Ordnance Factory

Waterton Site.

The primary function of the Bridgend ROF Waterton site when it was first planned was, as a bomb filling factory, it would produce gun cotton and cordite for Navy and Army ordnance. (See appendix 3)

Prior to 1939 production had been concentrated at Waltham Abbey and the Woolwich Arsenal sites.

In 1934 the government started planning the relocation of ordnance production to remoter sites in the West and North West of the UK.

Bridgend was one of the chosen sites because it met all of the governments criteria, it had the right infrastructure and constituent parts such as land, labour, material, plus road, rail and sea communications.

Construction of the works started in 1937 with planned production set for July 1940 when conflict with the 3rd Reich was expected to develop into a full-scale war.

At the planning stage production targets were set to meet the anticipated Army and Naval requirements. These were for 126,000 rounds a week for the Army, and 77,000 rounds a week for the Navy.

Gun Cotton.

Gun cotton was discovered in 1845 by C.F. Schonbein and independently by Bottger in 1846, both collaborated to develop it into a new explosive.

Early attempts to manufacture this explosive on a large scale were problematic and it was not until new methods had been developed for freeing the nitrated cotton from the associated dangerous impurities could it be safely manufactured and stored.

Gun cotton is obtained by steeping cotton in nitric and sulphuric acids in a carefully controlled environment.

In appearance it resembles ordinary cotton and at normal temperatures is safe to handle in small quantities and in the open it will burn harmlessly. However, in confined areas it will explode if heated or ignited.

Its principle use is as an explosive filling for Naval and Artillery shells, with its secondary use in blasting.

Gun Cotton Manufacture.

There were eleven steps in the Gun Cotton manufacturing process, each step required separate shops plus specialist skills to maximise production and reduce the risk of catastrophic accidents.

In the spinning shops cotton wool fibres were spun into loose threads of sufficient strength so that they could be easily handled.


Gun Cotton Preparation and Coding Shop


The cotton was then thoroughly boiled in a solution of potash or soda, in order to remove all greasy substances, which the cotton may have contained, following this process the cotton was dried in a heated room. 

This drying room was heated to 100°F/23°C until it had thoroughly dried before it was passed on to the next process

Following drying the cotton was transported to the blending shops, which comprised of three separate tanks.  The first of these tanks contained a mixture of nitric acid of 1.48 to 1.50 specific gravity, whilst the second tank contained a solution of common sulphuric acid.

The third tank was used for receiving the cotton following the immersion process.

Gun Cotton Pulping and Blending Shop

Small parcels of dry and clean cotton wool fibre threads were then immersed in the first tank such that they were fully immersed in the nitric acid solution.

Following removal from this tank the cotton was gently pressed to release the surplus acid back into the blending tank. The impregnated cotton was then transferred to the next stage in the process.

The parcels of nitric acid impregnated cotton wool threads were then immersed in the sulphuric acid tank such that they too were fully immersed in the solution.

Following removal from this tank the cotton was again gently pressed to release the surplus sulphuric acid back into the blending tank before it was transferred to the next stage in the process.

The fully impregnated cotton parcels were then immersed in the 3rd tank in a solution of nitric and sulphuric acid.

Following this stage the cotton was removed from the tank and was gently pressed to release the surplus acids back into the mixing tank.

The fully impregnated cotton was then centrifuged in constant stream of water to remove from the cotton fibres all of the unwanted impurities that may have adhered to the acids.

Next the impregnated cotton was removed to a scouring tank to extract the last vestiges of impurities; this process usually took several days.

The impregnated cotton was dried then immersed in a solution of Beaume, which helps preserve and stabilise the gun cotton material.

Finally the gun cotton material was subjected to a final soft water (free of lime) cold water rinse before drying and assembling into shells and torpedoes.


The plant had to produce sufficient gun cotton to meet the Naval and Army requirements. Unfortunately, at this time no actual production figures are available, but based on the filling requirements the plant would have had to produce at least a 500 tons of gun cotton a week; some 20,000 tons per annum to meet requirements.

In the main the Gun Cotton Facility was located at the South Eastern end of the Waterton site near the Pyro and Textile shops.

The gun cotton was used in Naval Bags as an explosive for naval shells and large artillery shells, and was processed in several shops in the HE section of the Waterton site. (See appendix 12 and Waterton Chapter)

There were all of the usual problems associated with the manufacture of explosive materials, such as:

Waste Water.

At the time the process was introduced disposal of contaminated wastewater was into the local sewerage main or into the storm water drains the fed the local Ewenny River.

Later on in 1942 the subject of water treatment and waste were dealt with when a 19” diameter sewerage main was constructed that pumped these waste waters out to the Tusker rocks in the Bristol Channel beyond the ebb tide barrier. (See Waste Chapter in the War Folder)

The rinse water contaminants contained traces of potash, soda, nitric acid and sulphuric acid.

Health Hazards.

There were also a number of health problems; these covered handling, the inhalation of fumes, cotton fibres and ingestion of chemicals.

From recent studies published elsewhere it is now known that the fumes cause chest and psychological problems amongst workers employed in the production of Gun Cotton.


Storage too was a significant problem area as Gun Cotton is very flammable and may explode or ignite without warning when dry or too hot.

In the main the bulk storage was contained within five of the magazine storage tunnels at the Brackla Hill site, these were environmentally controlled to maintain a constant temperature and humidity. (See the 8X’s Chapter)

J.D.V. Ludlow

29 December 2023

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