# Color-changing glass - how does it work?

**URL:** <https://boards.straightdope.com/t/color-changing-glass-how-does-it-work/145941>\
**Category:** Factual Questions\
**Created:** [December 31, 2002, 9:30pm UTC](https://boards.straightdope.com/t/color-changing-glass-how-does-it-work/145941 "2002-12-31T21:30:53Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![dna\_man](https://avatars.discourse-cdn.com/v4/letter/d/d2c977/32.png) [@dna\_man](https://boards.straightdope.com/u/dna_man)\
**Post date:** [December 31, 2002, 9:30pm UTC](https://boards.straightdope.com/t/color-changing-glass-how-does-it-work/145941/1 "2002-12-31T21:30:53Z")

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Why does color-changing glass, commonly used in smoking accessories, change color? I’ve noticed that it seems to change color as the inner surface gets dirty, and will change back if cleaned. What gives?

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**Author:** ![Duck\_Duck\_Goose](https://avatars.discourse-cdn.com/v4/letter/d/50afbb/32.png) [@Duck\_Duck\_Goose](https://boards.straightdope.com/u/Duck_Duck_Goose)\
**Post date:** [January 1, 2003, 6:18am UTC](https://boards.straightdope.com/t/color-changing-glass-how-does-it-work/145941/2 "2003-01-01T06:18:04Z")

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Is the only place they use color-changing glass in bongs and pipes, or what? 😕 'Cause that’s all Google’s giving me.

Anyway, found this.

[http://shop.grasscity.com/cgi-bin/grasscity/faq\_color\_effect.html](http://shop.grasscity.com/cgi-bin/grasscity/faq_color_effect.html)

> [@](#):
>
> How do they get those colors in there? What is responsible for the “color change” effect?
> 
> Small pieces of metal (usually silver and/or gold) are held in the flame of the torch until vaporized (often called ‘fuming’). The glass is rotated in this vapor stream until a fine layer of the vaporized metal is visible on the surface of the glass. After this, clear glass is applied (often in ‘dots’ and ‘lines’) to ‘encase’ the vaporized metal in between layers of glass. There are many techniques and methods of applying the fumes and clear glass making a myriad of different colors, and endless types of patterns that one can come up with. The colors produced with fumed metals are best when they are translucent, vibrant, and reflective. As the pipe darkens with use, the colors (many barely visible) become darker and much more conspicuous, thus causing the appearance of ‘color change’ (the glass doesn’t really change colors though).