Gunpowder was very expensive, largely because of the monopoly on saltpetre. It was made by grinding charcoal, sulphur and saltpetre together in ‘incorporating mills’. The process was complex and extremely dangerous. At all stages the mixture was unstable to a greater or lesser degree.

Gunpowder was imported into Cornwall until 1808 when the first Cornish gunpowder factory opened: at Cosawes Wood, Perran-ar-Worthal, about 5 miles from Falmouth. The site at Cosawes and at other works - such as the one at nearby Kennall Vale which followed in 1813 - were chosen for their seclusion in wooded river valleys. This ensured both the availability of water power and the relative safety of nearby settlements, shielded as they were by the trees. The roofs of the factory buildings were also designed to blow off relatively harmlessly in the event of an explosion.

The Kennall Vale Works (Scheduled Monument), originally a subsidiary of the Fox family’s Perran Foundry Company,was built to a substantial and technologically advanced design in 1812 and expanded by 1835. © Barry Gamble.

The adoption of gunpowder represented a great technological breakthrough. In 1836 alone, 30 tonnes of gunpowder were used in Cornish mines. The first practical high-explosive ever fired in a mine was in the Restormel Iron Mine (managed by John Taylor) at Lostwithiel in 1846. By the 1860s high explosives were being used far more efficiently and had become far more refined. In 1866, Alfred Nobel (1833-96) invented dynamite. This nitroglycerine-based explosive reached Britain the following year and Cornwall soon after. The principal Cornish gunpowder manufacturer - Shilson - set up the National Explosives Company in 1888.

British & Colonial Explosives Company works (1891). © Barry Gamble.

The first factory was built amidst the protective environment of Hayle Towans and soon became one of the leading manufactories in Britain. In 1889 the British & Colonial Explosives Company was formed. The site chosen for the new factory was a hectare of remote old mining ground at St George’s Common on the cliffs west of Perranporth. Extensive structures survive, both at Hayle and at Perranporth.