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.
