Crown glass (window)


Crown glass (window)
Crown Glass

Crown glass was an early type of window glass. In this process, glass was blown into a "crown" or hollow globe. This was then transferred from the blowpipe to a pontil and then flattened by reheating and spinning out the bowl-shaped piece of glass (bullion) into a flat disk by centrifugal force, up to 5 or 6 feet (1.5 to 1.8 metres) in diameter. The glass was then cut to the size required.[1]

The thinnest glass was in a band at the edge of the disk, with the glass becoming thicker and more opaque toward the center.

Due to the distribution of the best glass, in order to fill large window spaces many small diamond shapes would be cut from the edge of the disk and these would be mounted into a lead lattice work and fitted in the window. Known as a bullseye, the thicker center area around the pontil mark was used for less expensive windows.

Crown glass was one of the two most common processes for making window glass until the 19th century. The other was blown plate. The process was first perfected by French glassmakers in the 1320s, notably around Rouen, and was a trade secret. As a result, crown glass was not made in London until 1678.

Crown glass is one of many types of hand-blown glass. Other methods include: broad sheet, blown plate, polished plate and cylinder blown sheet. 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, single and twin ground polished plate and float glass.[2]

References


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Look at other dictionaries:

  • Crown glass — is either of two kinds of glass: Crown glass (window) was a type of hand blown window glass. Crown glass (optics) is a type of optical glass used in lenses. This disambiguation page lists articles associated with the same title. If an …   Wikipedia

  • Crown glass (optics) — This article is about crown glass as used in optics. For the window glass, see Crown glass (window). Crown glass is type of optical glass used in lenses and other optical components. It has relatively low refractive index (≈1.52) and low… …   Wikipedia

  • Crown glass — Glass Glass (gl[.a]s), n. [OE. glas, gles, AS. gl[ae]s; akin to D., G., Dan., & Sw. glas, Icel. glas, gler, Dan. glar; cf. AS. gl[ae]r amber, L. glaesum. Cf. {Glare}, n., {Glaze}, v. t.] [1913 Webster] 1. A hard, brittle, translucent, and… …   The Collaborative International Dictionary of English

  • crown glass — crown′ glass n. 1) opt cer an optical glass of low dispersion and generally low index of refraction 2) cer an old form of window glass formed by blowing a globe and whirling it into a disk • Etymology: 1700–10 …   From formal English to slang

  • crown glass — n. 1. window glass made in flat, circular plates by blowing and whirling, with a small knot in the center left by the blower s rod 2. a very clear optical glass with a low index of refraction …   English World dictionary

  • crown glass — noun 1. a glass blown into a globe which is later flattened and spun to form a disk • Hypernyms: ↑glass 2. optical glass of low dispersion and low refractive index • Syn: ↑optical crown, ↑optical crown glass • Hypernyms: ↑optical glass …   Useful english dictionary

  • crown glass — 1. an optical glass of low dispersion and generally low index of refraction. 2. an old form of window glass formed by blowing a globe and whirling it into a disk. [1700 10] * * *       handmade glass of soda lime composition for domestic glazing… …   Universalium

  • crown glass — /ˈkraʊn glas/ (say krown glahs) noun 1. an optical glass of low dispersion and generally low refractive index. 2. an old form of window glass formed by blowing a globe and whirling it into a disc, composed essentially of soda, lime, and silica;… …   Australian English dictionary

  • Window glass — Glass Glass (gl[.a]s), n. [OE. glas, gles, AS. gl[ae]s; akin to D., G., Dan., & Sw. glas, Icel. glas, gler, Dan. glar; cf. AS. gl[ae]r amber, L. glaesum. Cf. {Glare}, n., {Glaze}, v. t.] [1913 Webster] 1. A hard, brittle, translucent, and… …   The Collaborative International Dictionary of English

  • Glass — (gl[.a]s), n. [OE. glas, gles, AS. gl[ae]s; akin to D., G., Dan., & Sw. glas, Icel. glas, gler, Dan. glar; cf. AS. gl[ae]r amber, L. glaesum. Cf. {Glare}, n., {Glaze}, v. t.] [1913 Webster] 1. A hard, brittle, translucent, and commonly… …   The Collaborative International Dictionary of English


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