# Glass "waves"

**URL:** <https://boards.straightdope.com/t/glass-waves/272307>\
**Category:** Factual Questions\
**Created:** [November 1, 2004, 1:10pm UTC](https://boards.straightdope.com/t/glass-waves/272307 "2004-11-01T13:10:36Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![CaryGMcC](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@CaryGMcC](https://boards.straightdope.com/u/CaryGMcC)\
**Post date:** [November 1, 2004, 1:10pm UTC](https://boards.straightdope.com/t/glass-waves/272307/1 "2004-11-01T13:10:36Z")

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Can anybody offer a good explanation as to why glass, especially so-called “plate glass” appear somewhat wavy, especially the reflection?  
I have observed that tempered glass seems to cast a slightly more distorted reflection than ordinary, old-fashioned window glass.

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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:** [November 1, 2004, 2:19pm UTC](https://boards.straightdope.com/t/glass-waves/272307/2 "2004-11-01T14:19:41Z")

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Waves are caused by either surface imperfections (older window glass) or by differences in density within the glass caused by internal stresses (tempered glass). Laminated safety glass, such as used in car windshields, may also show some ‘rainbow’ fringing due to slight variations in the lamination layers.

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**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\
**Post date:** [November 1, 2004, 9:00pm UTC](https://boards.straightdope.com/t/glass-waves/272307/3 "2004-11-01T21:00:20Z")

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Cecil did a piece on this, but I’m too lazy to look it up.