Reasons for Designation
Glass has been produced in England since the Roman period, although field
evidence is scarce until the late medieval period. Wood was the main
manufacturing fuel up to the early 17th century, so the industry was located
in woodland areas, particularly the Weald. From about 1610, production shifted
to the coalfields.
Glass production requires three major components: silica, alkali and lime,
together with colouring material for certain products and decolourisers for
clear glass. Lead was also used in the production of certain types of glass
during the Roman period and after the 17th century. The manufacturing process
involves three stages, fritting, melting and annealing. Fritting was a common
practice before the 19th century involving heating the main glass constituents
to produce an unmolten material for grinding, melting and annealing. Melting
involved the remelting of previously formed glass, and the production of new
glass from raw materials. Until the late 19th century, glass was normally
melted in pre-fired crucibles of refractory clay, on stone benches called
sieges, within the melting furnace. Use of coal as the preferred fuel and
automatic bottle-making machinery in the 1880s led to changes to the melting
furnaces and the use of larger furnaces, hitherto conical structures over
circular furnaces. Regenerative furnaces were developed in the 1860s, and tank
furnaces for bulk melting quickly followed. Flat-glass production methods were
made obsolete by the Pilkington float-glass system of 1959. The third process
is annealing. Because the rapid cooling of molten glass can give rise to
internal stresses, glass was treated in furnaces designed to heat the glass to
a point where deformation begins, then cooled gradually. In the 19th century
conveyors were introduced to take glass through a hot zone into cool air.
Features on glass manufacturing sites include various types of furnaces,
producer-gas plants for the making of gas from coke at 19th century
glassworks, bottle-making machinery, blowing irons or pipes for blowing glass,
glass residues and various buildings used as stores or warehouses. A total of
135 glass production sites (representing about 25% of the estimated national
archaeological resource for the industry) have been identified as being of
national importance. This selection, compiled and assessed though a
comprehensive national survey of the glass industry, is designed to represent
the industry's chronological depth, technological breadth and regional
diversity, and to include all the better preserved glass sites, together with
rare individual component features.
Despite the lack of surface evidence, the buried remains of Maryport glass
house survive reasonably well. The monument is an exceptionally
well-documented small 18th century glass bottle works, and is a rare example
of this class of monument to offer the opportunity for further study of
furnace and annealing ovens together with the range of associated buildings
such as the clay mill, clay, bottle, kelp and korker stores. It dates from a
period of experimentation with furnace and crucible design and as such has the
potential to include innovative features.
Details
The monument includes the buried remains of Maryport glass house, an 18th
century bottle manufacturing works located between Irish Street and the River
Ellen 200m north of Mote Hill. It is not known for certain when bottle
manufacturing began here but a map of 1745 depicts the glass house. An
advertisement for the sale of the glass house in 1773 mentions ancillary
buildings such as the korker and ash houses. A plan of the glass house
produced during the 1780s depicts the circular cone containing melting
furnaces together with three annealing furnaces and two flue entrances. The
melting furnaces facilitated the re-melting of previously-formed glass, the
production of new glass from raw materials, or a combination of the two
activities whereby new materials were mixed with broken glass known as cullet.
The glass was melted in clay crucibles placed in the furnace. The rapid
cooling of molten glass gives rise to internal stresses and deformation and
unless annealed the glass will readily shatter. The annealing furnaces here
facilitated the process of re-heating previously molten glass to a temperature
below the point where deformation begins. The glass was then gradually cooled
thus resulting in a considerably strengthened finished product. The 1780s map
also depicts a number of ancillary buildings including a clay store and clay
mill for producing the crucibles, a bottle store, and a kelp store where
seaweed used as an alkali in the glass-making process was stored. One other
building shown on the 1780s map of the glass house is a korker store. Korker
is an obscure term, possibly a corruption of the word celcar, which refers to
the main constituents of glass which have been partially heated to produce an
unmolten material which could be ground up ready to place in the crucible for
the main melt. The more familiar term for this process is fritting thus the
korker store is considered to represent the store room for fritted material
awaiting the final melt.
The glass house is thought to have ceased production towards the end of the
18th century and by 1803 the site had been taken over by shipbuilders John
Peat & Co. During the mid-to late 1980s parts of the glass house were exposed
during land grading operations. Remains of the clay mill and store together
with remains of the korker store were visible, while the cone and furnace area
appeared relatively undisturbed. These remains have since been reburied.
All fence posts, gateposts, railings and the retaining wall on the west bank
of the River Ellen are excluded from the scheduling although the ground
beneath these features is included.
MAP EXTRACT
The site of the monument is shown on the attached map extract.
