One the best-preserved industrial archaeology sites in Ireland is a well-hidden secret in Ballincollig, Co. Cork. In 1794 two Corkmen established the gunpowder mills on the banks of the River Lee, at Ballincollig, five miles from Cork city. The gunpowder factory was in operation for over 100 years until it finally closed in 1903. The isolated site meant that the site was never used again or redeveloped and from 1983 Cork County Council has been restoring the site as part of the Ballincollig Regional Park. The site was first opened to the public as a visitor attraction in 1988. The entrance is off the main Cork-Killarney road, in the centre of Ballincollig, adjacent to the old barracks.
For the chemistry teacher the Royal Gunpowder Mills has a special attraction as it is an example of one of Ireland's early chemical industries [1], illustrating some interesting chemistry, and with a great attraction for young people - an ideal place for a school trip. The name 'Gunpowder Mills' derives from the fact that gunpowder manufacture traditionally used water-powered mills for grinding the ingredients together to make gunpowder, which is a an intimate mixture of potassium nitrate (saltpetre), sulphur and carbon (charcoal). Obviously naked lights and fires mustn't be used around explosives and so water-power rather than steam-power was used as a source of power. The restored part of the extensive Ballincollig site consists of a series of gunpowder mills, powered by water brought by canal from the River Lee nearly 2 miles upstream and then released back into the river. A pollution-free and free source of energy.
The rest of the 130 acre site stretches over one and a half miles alongside the southern bank of the Lee. The buildings were originally linked by a network of canals, which were used to transport the raw materials and products. The various buildings were dispersed over the site, keeping the various stages of the process widely separated as a safety precaution. The map below shows the size of the site and the many buildings dotted over it, many of them in ruins and unrestored. The site has a visitor centre with a display on the manufacture of gunpowder and the history of the site, and a video telling the story of the site and how gunpowder was made. Guided tours are available of the various grinding (known as incorporating mills), one of which has been restored to working order, and the charge houses where the materials were stored. A pleasant walk through the park leads you eventually to the entrance/gatehouse and the Iniscarra Bridge.
Figure 1 shows the extent of the site along the River Lee, taken from the site leaflet. The shaded area is the restored area.
Charcoal was made on the site and potassium nitrate and sulphur were imported and purified, ready for

blending - a process known as incorporating - into the black powder known as a gunpowder. Barrels were also made on the site for shipping out the product.

The History
The mills have changed ownership over the years and closed at times as the demand for gunpowder waxed and waned. The factory was started in 1794 by Charles Henry Leslie and John Travers. In 1804 Leslie bought out Travers and in 1805 the British Board of Ordnance bought the mills from Leslie, in the face of the threat from Napoleon. They built the main canal, increased the capacity tenfold and built an army barracks adjacent to the site to protect the works. In 1815 after the defeat of Napoleon, the mills were closed for 20 years and the buildings decayed, equipment was sold off and the canals silted up. Revival came when two Liverpool merchants, Thomas Tobin and Charles Horsfall, bought the site in 1834, refurbished them and started production again. In the next 20 years the mills expanded in size and production - from 200 workers in 1837 to over 500 twenty years later. The owners were enlightened employers and built houses for workers and their families near the mills. As gunpowder gave way to more powerful explosives like dynamite, nitroglycerine and guncotton the market for gunpowder declined.

In 1888 the mills were bought by John Briscoe and in 1898 they came under the control of Curtis and Harvey. This was period of rationalisation in the explosives industry and after a mini-boom during the Boer War, the mills were closed for good and production ceased in June 1903. Curtis and Harvey became in turn part of Nobel industries, which became part of Imperial Chemical Industries in 1926 and ICI became owners of the site, retaining and interest in it until 1971. In 1983 Cork County Council took over the site and started to restore it.

The Manufacture of Gunpowder
The manufacture of gunpowder is essentially one of mixing the ingredients in the correct proportions, and then grinding them into a fine powder to ensure thorough mixing and a small particle size to provide rapid burning.

The incorporating mills were at the heart of the process, and are the main attraction at the restored site. Batches of 'green charge' were mixed in the batch houses and then taken to the incoporating mills. The materials were mixed damp to reduce the risk of explosions. The 'mill cake' was transported along the canal to the press house, where it is was s squeezed to remove moisture. The 'press cake' was broken into small pieces and sent to the corning mill, where small grains of powder were produced. Different sizes produce different burning rates and thus different grades of powder. The grains were then dried in the stove house and the dry grains were glazed with graphite powder to repel water, and presumably reduce friction also. The resulting black powder was bagged or put into barrels, stored in magazines and then shipped out via the port of Cork to purchasers in Britain or abroad. Peak production (1877) was 32,000 barrels of gunpowder per year. The barrel contained 100lb. ( 45.36kg) of gunpowder, with twenty barrels to the short ton of 2,000lb.

Opening hours:
Easter to end of September; 10 a.m. to 6 p.m. daily
For information check:
www.cork-guide.ie/attractions/gunpmill.htm