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.
Details
The monument includes the earthworks and buried remains of a late medieval
glassworking site in Delamere Forest. The site was identified in 1933 and
partially excavated during 1933-5. The excavations revealed a dense
concentration of glass fragments including painted glass imported to the
site as cullet (scrap glass for remaking). In addition a glazed brick
floor was uncovered and this may be a part of the original furnace floor.
Crucible fragments confirm the presence of glassmaking here. Building
stone on the site and reused material in the field walls bears traces of
spilled glass. Associated with these remains were sherds of 15th century
pots and a silver penny of Edward I.
The site was further examined by excavation in 1947 and the report
concluded that the area of the glassmaking debris covered about 12 sq m,
and that there were probably more remains to be discovered in the
immediate vicinity. The excavators thought that the production of glass
at this location was confined to window glass, both clear and coloured,
and that the furnace was fired with wood from the forest around it. Work
probably ceased here when the use of wood was forbidden by law in royal
forests in about 1615. However, there is a plan of the forest dating to
1627, which marks this site as `Glassen House'.
A concrete footbridge crossing the brook in the centre of the site is
excluded from the scheduling, although the ground beneath it is included.
Legacy
The contents of this record have been generated from a legacy data system.
Legacy System number:
33880
Legacy System:
RSM
Sources
Books and journals Other
Legal
This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Culture, Media and Sport.
End of official list entry
