Polished plate is a type of hand-made

glass Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling ( quenching ...

. It is produced by casting glass onto a table and then 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 Broad sheet is a type of hand-blown glass. It was first made in Sussex in 1226. Production It is made by blowing molten glass into an elongated tube shape with a blowpipe. Then, while the glass is still hot, the ends are cut off and the resu ...

blown plate Blown plate is a hand-blown glass. There is a record of blown plate being produced in London in 1620. Production Blown plate was made by hand-grinding broad sheet glass. As the process was labour-intensive, and expensive, blown plate was mainly use ...

, 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 iron mold. The ends are cut off an ...

. 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 Rolling is a type of motion that combines rotation (commonly, of an axially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exist, the two are in contact ...

machine drawn cylinder sheet Machine drawn cylinder sheet was the first mechanical method for "drawing" window glass. Cylinders of glass 40 feet (12 m) high are drawn vertically from a circular tank. The glass is then annealed and cut into 7 to 10 foot (2 to 3 ...

flat drawn sheet Flat or flats may refer to: Architecture * Flat (housing), an apartment in the United Kingdom, Ireland, Australia and other Commonwealth countries Arts and entertainment * Flat (music), a symbol () which denotes a lower pitch * Flat (soldier), a ...

single and twin ground polished plate Single may refer to: Arts, entertainment, and media * Single (music), a song release Songs * "Single" (Natasha Bedingfield song), 2004 * "Single" (New Kids on the Block and Ne-Yo song), 2008 * "Single" (William Wei song), 2016 * "Single", by ...

, and float glass. The Frenchman, Louis Lucas de Nehou, in 1688, in conjunction with Abraham Thevart, succeeded in perfecting the process of casting plate-glass. Mirror plates previous 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 Ravenhead is an area of St Helens in the North West of England. It is bordered by Thatto Heath, Sutton and the Town Centre. The area is thought to take its name from a farm once located nearby (Ravenhead Farm), while the 'head' portion of the n ...

. By 1800 a steam engine was used to carry out the grinding and polishing of the cast glass.

References

Glass production Glass types {{Glass-engineering-stub