# Water turns blue in reaction to red wine

**URL:** <https://boards.straightdope.com/t/water-turns-blue-in-reaction-to-red-wine/139570>\
**Category:** Factual Questions\
**Created:** [November 30, 2002, 12:15am UTC](https://boards.straightdope.com/t/water-turns-blue-in-reaction-to-red-wine/139570 "2002-11-30T00:15:58Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Koxinga](https://avatars.discourse-cdn.com/v4/letter/k/4af34b/32.png) [@Koxinga](https://boards.straightdope.com/u/Koxinga)\
**Post date:** [November 30, 2002, 12:15am UTC](https://boards.straightdope.com/t/water-turns-blue-in-reaction-to-red-wine/139570/1 "2002-11-30T00:15:58Z")

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I notice that when I’m washing out a cup stained with the residue of (rather cheap) red wine, the water immediately turns a deep blue very different from the color of the original wine. What kind of chemical reaction is going on here?

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**Author:** ![mnemosyne](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@mnemosyne](https://boards.straightdope.com/u/mnemosyne)\
**Post date:** [November 30, 2002, 12:29am UTC](https://boards.straightdope.com/t/water-turns-blue-in-reaction-to-red-wine/139570/2 "2002-11-30T00:29:46Z")

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Wow… I’ve never noticed that before. I’m going to have to check it tonight after supper when I wash out my wine glass!

The only things I can think of off-hand would be some sort of reaction with copper to give Cu(2+)…I think thats the blue one…maybe 3+? I forget. Anyways, solutions of one of the copper ions are blue, and so maybe there is some sort of exchange going on that’s causing copper to become free in the solution? I’m guessing the copper might come from your water pipes, but I don’t remember my chemistry well enough to say what might be causing it specifically. Sounds pretty cool, though!

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**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\
**Post date:** [November 30, 2002, 1:04am UTC](https://boards.straightdope.com/t/water-turns-blue-in-reaction-to-red-wine/139570/3 "2002-11-30T01:04:46Z")

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Your wine may be acting as a pH indicator. Try a little lemon juice or household ammonia and see if you get the same color change.