Reasons for Designation
Gunpowder was the only explosive available for military use and for blasting
in mines and quarries until the mid-19th century. Water-powered manufacturing
mills were established in England from the mid-16th century, although powder
had been prepared by hand for at least 200 years. The industry expanded until
the late 19th century when high explosives began to replace gunpowder. Its
manufacture declined dramatically after the First World War with British
production ceasing in 1976. The technology of gunpowder manufacture became
increasingly complex through time with the gradual mechanisation of what were
essentially hand-worked operations. Waterwheels were introduced in the 16th
century, and steam engines and water turbines from the 19th century. Pressing
and corning were also introduced between the 16th and 19th centuries to
improve the powders. Pressing improved the explosive power of the mill cake
and corning broke the pressing cake into different sizes and graded it with
respect to its fineness. Additional techniques were developed throughout the
17th, 18th and 19th centuries to improve the quality and consistency of the
finished product, and this in turn resulted in a variety of types of powders;
ranging from large coarse-grained blasting powders used in mines and quarries,
to fine varieties used, for example, in sporting guns.
Gunpowder manufacturing sites are a comparatively rare class of monument with
around 60 examples known nationally. Demand for gunpowder centred on the
London area (for military supply), other ports (for trade), and the main metal
mining areas. Most gunpowder production was, therefore, in Cumbria, the south
west, and the south east around the Thames estuary. The first water-powered
mills were established in south east England from the mid-16th century
onwards, and many of the major technological improvements were pioneered in
those mills. All sites of gunpowder production which retain significant
archaeological remains and technological information and survive well will
normally be identified as nationally important.
Despite conversion of part of the monument into a caravan site, much of the
northern and central parts of New Sedgwick gunpowder works still survive well
and it remains one of the better preserved 19th/early 20th century gunpowder
works in northern England. It retains many of its structural components,
including the remains of nine incorporating mills, corning mills, an engine
house, a dusting house, stove houses, glaze houses, a pump house, a press
house, a saltpetre refinery, a boiler station, stables and a joiner's shop,
together with large parts of the water management system which powered the
waterwheels and water turbines. Many of these surviving buildings preserve
technological information relating to their 19th and 20th century use. Buried
remains of other associated buildings depicted on site plans will also
survive.
Details
The monument includes an upstanding building, the ruins, earthworks and buried
remains of the northern and central parts of New Sedgwick gunpowder works,
located on the west bank of the River Kent approximately 1km NNW of Sedgwick
village. The gunpowders manufactured at New Sedgwick mainly comprised course
powders used for mining, quarrying and other blasting activities, and the
remains include a number of structures and ancillary buildings associated with
aspects of this manufacturing process, together with a weir and part of the
water management system constructed to provide water power for some of the
gunpowder production processes.
Gunpowder production consists of eight principal stages: preparation and first
mixing of the main ingredients of saltpetre, sulphur and charcoal,
incorporating these ingredients by mixing and grinding, pressing of the
mixed powder into a `cake' to improve its specific gravity and explosive
power, corning or breaking up and sizing of the press cake, dusting of the
sized powder to remove loose particles, glazing of the gunpowder to protect
against moisture, drying in a heated building known as a stove house or drying
house, then finally packing or moulding in barrels or cartridges. Each of
these processes took place in purpose-built structures, some of which were
located away from the main group of buildings because of the danger of
explosion, and remains of many of these, including corning mills, a dusting
house, stove houses, glazing houses, press houses, pump houses, a saltpetre
refinery, a boiler house, powder houses, an engine house and incorporating
mills survive at New Sedgwick.
The original licence to manufacture gunpowder at New Sedgwick was granted to
Walter Charles Strickland of Sizergh Castle in 1857 and production began the
following year. In 1864 the company failed but the business was reconstructed
by the Sedgwick Gunpowder Company. Rationalisation of the gunpowder industry
led to a merger with the Nobel organisation shortly after the end of World
War I but falling orders led to eventual closure in 1935. Following Board of
Trade regulations many of the buildings were subsequently dismantled and/or
burned to ensure no explosives could remain in crannies.
A weir, of which fragments survive, was constructed across the River Kent
upstream from the gunpowder works, and from it a large stone-lined mill race
was cut to provide water for waterwheels and turbines to power the machinery.
An electric engine was also used as an alternative power source. The remains
of the gunpowder works are described from north to south; the ruins of a
building sandwiched between the mill race and the river are those of the top
corning house, and a short distance to the south are the ruins of a dusting
house. Further south, on the west side of the mill race, stand the remains of
the new stove house and chimney where the gunpowder would have been placed to
dry, while a short distance to the south lie the footings of the old stove
house which it replaced. Opposite this latter building, on the east of the
mill race, are a wheelpit and the ruins of glazing houses, while a short
distance to the south are remains of a building variously described as a
corning mill and a glaze house. To the east of a bridge across the mill race
are two substantial earthen blast-banks between which ran the tramway used for
transporting powder around the works. Although no surface remains are visible,
a site plan depicts an early corning house located immediately to the south of
the eastern blast bank. On the west of the mill race a tramway cutting leads
to the ruins of a cartridge press house, while flanking the eastern side of
the mill race are remains of a corning mill with attendant blast banks, a
powder press pump house and a cartridge press house. A short distance to the
south stand remains of nine incorporating mills arranged as a group of six and
a group of three, with a tall blast wall separating the two groups. Here the
gunpowder ingredients were crushed and ground together under heavy edge
grinding runners to form mill cake. Large waterwheels powered the grinding
stones, meaning that the design of an incorporating mill is instantly
recognisable as identical structures either side of a waterwheel with a tail
race taking used water away.
When the mills were burned at the closure of the works, the light wooden-
framed huts that enclosed each mill were burned to the ground leaving only the
thick stone-built three-sided outer blast walls. To the south of the
incorporating mills, on the east side of a leat, are remains of a green charge
house or unprocessed powder store. To the north are remains of a ripe charge
house where the incorporated powder was stored. To the south, site plans show
the location of the preparing house where the gunpowder ingredients were
measured out and given an initial mix; buried remains of this structure will
survive. On the eastern side of the monument, close to the river, stands an
electric motor house which powered machinery in the now demolished adjacent
dust house. Site plans show that a cartridge press house and a heading house
were also located in the vicinity and buried remains of these structures will
also survive. To the south lie the remains of a group of buildings
collectively known as `Black Pot'; these consisted of the saltpetre refinery,
a boiler station, stables and a joiner's shop. Site plans show that a powder
packing house was located close to the point where the tailrace exits into the
river, and buried remains of this building will also survive.
The gunpowder works originally extended further south to the gatehouse which
provided access to the complex. Workshops and offices originally occupied this
southern area. Some of these buildings survive to some degree but they have
remained in use and are not included in the scheduling.
A number of features are excluded from the scheduling; these are all modern
buildings, barriers, signposts, electrical hook-up points and water points
associated with the caravan site, the surface of all roads, tracks, paths, car
parks and caravan pitches, a timber walkway flanking a glaze house, all
flagged areas, all modern bridges, and all modern walls, fences and railings,
although the ground beneath all these features is included.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
