# Tanning through glass?

**URL:** <https://boards.straightdope.com/t/tanning-through-glass/249780>\
**Category:** Factual Questions\
**Created:** [June 11, 2004, 4:29am UTC](https://boards.straightdope.com/t/tanning-through-glass/249780 "2004-06-11T04:29:38Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Atticus\_Finch](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Atticus\_Finch](https://boards.straightdope.com/u/Atticus_Finch)\
**Post date:** [June 11, 2004, 4:29am UTC](https://boards.straightdope.com/t/tanning-through-glass/249780/1 "2004-06-11T04:29:38Z")

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I realise this is likely to have been answered before, but I couldn’t see it when I searched.

Anyway, is it true that you tan less if the sun is shining through glass? That is, does common window glass block some wavelengths of UV light or something like that? A friend suggested this was the case, but didn’t have any evidence when asked.

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**Author:** ![Eleusis](https://avatars.discourse-cdn.com/v4/letter/e/f4b2a3/32.png) [@Eleusis](https://boards.straightdope.com/u/Eleusis)\
**Post date:** [June 11, 2004, 4:44am UTC](https://boards.straightdope.com/t/tanning-through-glass/249780/2 "2004-06-11T04:44:08Z")

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[http://www.straightdope.com/classics/a1\_163b.html](http://www.straightdope.com/classics/a1_163b.html)

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**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\
**Post date:** [June 11, 2004, 4:45am UTC](https://boards.straightdope.com/t/tanning-through-glass/249780/3 "2004-06-11T04:45:27Z")

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Yes, window glass block the vast majority of shortwave UV-B and UV-C, which causes the most tanning (and skin damage), while passing most of the longer wavelength UV-A, which gives very little tanning results.

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**Author:** ![Atticus\_Finch](https://avatars.discourse-cdn.com/v4/letter/a/ec9cab/32.png) [@Atticus\_Finch](https://boards.straightdope.com/u/Atticus_Finch)\
**Post date:** [June 11, 2004, 5:10am UTC](https://boards.straightdope.com/t/tanning-through-glass/249780/4 "2004-06-11T05:10:37Z")

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Too easy! Thanks, guys.

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**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\
**Post date:** [June 11, 2004, 6:44am UTC](https://boards.straightdope.com/t/tanning-through-glass/249780/5 "2004-06-11T06:44:28Z")

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The eight people locked inside Biosphere 2 were quite pasty after spending two years inside due to the UV blocking of the 1/2" glass. An unfortunate side effect was that bees did very poorly as pollinators as they were probably unable to identify UV images of flowers.