Polished plate is a type of hand-made
glass
Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...
. It is produced by casting glass onto a table and subsequently grinding and polishing the glass. This was originally done by hand, and then later by machine. It was an expensive process requiring a large capital investment.
Other methods of producing hand-blown window glass included:
broad sheet,
blown plate,
crown glass and
cylinder blown sheet
Cylinder blown sheet is a type of hand- blown window glass. It is created with a similar process to broad sheet, but with the use of larger cylinders. In this manufacturing process glass is blown into a cylindrical shape by a glass blower. The en ...
. These methods of manufacture lasted at least until the end of the 19th century. The early 20th century marks the move away from hand-blown to machine manufactured glass such as
rolled plate,
machine drawn cylinder sheet, flat drawn sheet,
polished plate glass, and
float glass
Float glass is a sheet of glass made by floating molten glass on a bed of molten metal of a low melting point, typically tin, although lead was used for the process in the past. This method gives the sheet uniform thickness and a very flat surfa ...
.
In 1688, the Frenchman Louis Lucas de Nehou, in conjunction with Abraham Thevart, succeeded in perfecting the process of casting plate-glass. Mirror plates prior to the invention had been made from blown "sheet" glass, and were consequently very limited in size. De Nehou's process of rolling molten glass poured on an iron table rendered the manufacture of very large plates possible.
[''Encyclopædia Britannica'' 11th edition (1911)]
In 1773 English polished plate (by the French process) was produced at
Ravenhead.
By 1800 a steam engine was used to carry out the grinding and polishing of the cast glass.
References
Glass production
Glass types
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