# Circular Distortions in London Windows

**URL:** <https://boards.straightdope.com/t/circular-distortions-in-london-windows/385454>\
**Category:** Factual Questions\
**Created:** [December 24, 2006, 5:22pm UTC](https://boards.straightdope.com/t/circular-distortions-in-london-windows/385454 "2006-12-24T17:22:41Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Richard\_Parker](https://avatars.discourse-cdn.com/v4/letter/r/35a633/32.png) [@Richard\_Parker](https://boards.straightdope.com/u/Richard_Parker)\
**Post date:** [December 24, 2006, 5:22pm UTC](https://boards.straightdope.com/t/circular-distortions-in-london-windows/385454/1 "2006-12-24T17:22:41Z")

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I’m traveling through Europe for the first time this holiday season, starting in London. I’m sure I’ll have lots of questions for The Dope, but this is my first: what are the circular distortions in windows around here? I’ve seen a number of windows in which the glass is distorted in such a way that it looks like someone has dropped a rock in a still pond. It is, uniformly, a 4-inch diameter circle with concentric waves terminating in the center. Is this a way to repair glass? Is it an artifact of the manufacturing process for old windows? Why don’t I see this in the US?

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**Author:** ![ticker](https://avatars.discourse-cdn.com/v4/letter/t/d07c76/32.png) [@ticker](https://boards.straightdope.com/u/ticker)\
**Post date:** [December 24, 2006, 5:37pm UTC](https://boards.straightdope.com/t/circular-distortions-in-london-windows/385454/2 "2006-12-24T17:37:08Z")

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See this site for a history of window glass: [Period Window Glass](http://www.ihbc.org.uk/context_archive/48/periodwindow.htm). The glass you are describing came originally from the center of the spun plate shown in the diagram at bottom of the page. Obviously it was far cheaper than that cut from the rest of the sheet. Most you see now is probably reproduction glass popular in 70’s along with several other crimes against architecture.

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**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\
**Post date:** [December 24, 2006, 5:40pm UTC](https://boards.straightdope.com/t/circular-distortions-in-london-windows/385454/3 "2006-12-24T17:40:22Z")

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“bullseye” glass may be produced deliberately these days, to reproduce old window glass, and is likely what you saw:

> **[Hand-blown Bullseye Window and Door Glass from Sugar Hollow Glass in...](https://www.sugarhollowglass.com/)**
>
> Sugar Hollow Glass designs and creates hand-blown, museum quality, authentic reproduction Bullseye Window Glass

Circular distortions USED to be an artifact of the “crown glass” manufacturing process. See notes in this wiki article:

> **[Architectural glass](https://en.wikipedia.org/wiki/Architectural_glass#Crown_glass:_The_earliest_style_of_glass_window)**
>
> Architectural glass is glass that is used as a building material. It is most typically used as transparent glazing material in the building envelope, including windows in the external walls. Glass is also used for internal partitions and as an architectural feature. When used in buildings, glass is often of a safety type, which include reinforced, toughened and laminated glasses.
> Glass casting is the process in which glass objects are cast by directing molten glass into a mould where it solidifi...